dissertation seaweed insulation
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Seaweed insulation
7. semester Dissertation
Author: Anna Katarzyna Plawecka
Consultant: Heidi Merrild
Date: October 2015
BATCoM–Bachelor of Architectural Technology and Construction Management
VIA University College, campus Horsens, Denmark
Anna Katarzyna Plawecka October 30, 2015
1
TITLE PAGE
BATCoM- Bachelor of Architectural Technology
and Construction Management
Elective title: Seaweed insulation
Consultant: Heidi Merrild
Author : Anna Katarzyna Plawecka
Date/signature: 30 October 2015
Student identity number: 187988
Number of copies: 1
No. of pages: 41
No. of characters: 63.895
Font: Calibri
All rights reserved – no part of this publication may be reproduced without the prior
permission of the author.
NOTE: This dissertation was completed as part of a Bachelor of Architectural Technology
and Construction Management degree course – no responsibility is taken for any advice,
instruction or conclusion given within!
Anna Katarzyna Plawecka October 30, 2015
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Preface
This report is a part of a final examination for the Bachelor of Architectural Technology
and Construction Management education at VIA University College.
The title of the report is “Seaweed insulation” and the aim of the report is to examine the
potential of seaweed as a modern insulation material.
I would like to thank everybody, who helped me while writing the report with good advice
and inspiration. First of all, I would like to thank my consultant, Heidi Merrild, who helped
me through the process of researching and writing the report. I would also like to thank
Gordon Alcock, who guided me through the rules of writing academic report.
Anna Katarzyna Plawecka October 30, 2015
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Abstract
The subject of the report is seaweed insulation. The aim of the report is to examine the
potential of seaweed as a modern insulation material. The report contains research on
usage of seaweed in building industry in the past as well as analyses of modern project
and production methods of building materials made out of seaweed. The the report
reflects also on material properties. Furthermore, research paper includes interview with
Flemming Werk from Advance Nonwoven (seaweed insulating mat producer) as well as
interview with Bodil E. Pallesen from AgroTech. Moreover, the report contains the brief
description of the seaweed workshop, two information sheets gathering main properties
of different types of seagrass and in the end an amateur experiment on eelgrass
inflammability.
The report starts form reflecting on history of seaweed in general and then it is going
deeper into specific role of this material in the building industry. Then it describes the first
attempts of using seaweed again in 2000s by Seaweed Triumvirate on Læsø. The papers
characterize in detail various aspects of the modern seaweed house, starting from
esthetics, through sustainability and economy, finishing at construction solutions. Then
the focus is turned on modern production process and the level of difficulty while working
with ready product. In the end, the report describes properties of seaweed and judges
threats connected with popularizing seaweed insulation.
The report concludes with the statement that seagrass has many virtues and can be
competitive insulation material on the market. However, more tests are needed in order
to examine deeply its properties. The threat is also insufficient amount of raw material in
case of starting a production on the bigger scale.
Key words
Seaweed/ seagrass/ eelgrass/ zostera marina/ posidonia oceanica insulation - New
biological insulation – History – Esthetics – Sustainability - Production process - Modern
applications - Properties
Anna Katarzyna Plawecka October 30, 2015
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Glossary
• Seaweed- general term to describe all the plants living in the sea. From biology
point of view seaweed is a marine alga and was never used to insulate houses.
(www.seagrasswatch.org)
• Seagrass- only flowering plant that can live underwater. From biology point of
view it has nothing to do with seaweed. Seagrass is an actual material which
was/is used to insulate houses. Commonly called seaweed.
(www.seagrasswatch.org)
• Zostera Marina- spices of seagrass. Appears in many places around the globe.
Commonly called eelgrass. In many publications called also seaweed.
(www.iucnredlist.org). For more information see enclosure 5.
• Posidonia Oceanica- spices of seagrass endemic to the Mediterranean Sea. Called
Neptune Grass or Mediterranean tapeweed. In many publications called also
seaweed. (www.iucnredlist.org) For more information see enclosure 6.
Anna Katarzyna Plawecka October 30, 2015
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Contents
1. Introduction with problem formulation ........................................................................ 9
1.1. Problem background information and presentation of the subject ...................... 9
1.2. Reasons for choice of the subject – personal relevance ........................................ 9
1.3. Problem statement ................................................................................................. 9
1.4. Delimitation .......................................................................................................... 10
1.5. Choice of theoretical basis and sources of empirical data ................................... 10
1.6. Choice of research methodology and empirical data ........................................... 10
1.7. Choice of working method .................................................................................... 10
2. Closer look on the seaweed ........................................................................................ 11
3. History of seaweed in building industry ...................................................................... 12
3.1. China ..................................................................................................................... 12
3.2. Denmark ................................................................................................................ 13
3.3. Netherlands .......................................................................................................... 16
3.4. USA ........................................................................................................................ 17
3.5. Part conclusion ...................................................................................................... 19
4. The seaweed triumvirate ............................................................................................. 20
4.1. Triumvirate´s activity ............................................................................................ 20
4.2. The gathering and Seaweed Bank idea ................................................................. 21
4.3. The construction methods .................................................................................... 22
4.4. Part Conclusion ..................................................................................................... 23
5. The modern seaweed house ....................................................................................... 24
5.1. The challenge ........................................................................................................ 24
5.2. Esthetics ................................................................................................................ 25
5.3. Sustainability ......................................................................................................... 26
5.4. Economy................................................................................................................ 27
5.5. Construction .......................................................................................................... 27
5.6. The future ............................................................................................................. 29
Anna Katarzyna Plawecka October 30, 2015
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5.7. Part conclusion ...................................................................................................... 29
6. Production of seaweed insulation and its application ................................................ 30
6.1. Seaweed insulation mats ...................................................................................... 30
6.2. Neptune Balls ........................................................................................................ 32
6.3. Part conclusions .................................................................................................... 33
7. Properties of seaweed ................................................................................................. 34
7.1. Thermal conductivity ............................................................................................ 34
7.2. Acoustic properties ............................................................................................... 34
7.3. Reaction to fire ..................................................................................................... 34
7.4. Lifespan and resistance to mold ........................................................................... 35
7.5. All the other virtues of seaweed ........................................................................... 36
7.6. Threats .................................................................................................................. 36
7.7. Part conclusion ...................................................................................................... 36
8. Conclusion ................................................................................................................... 37
Bibliography ......................................................................................................................... 39
Enclosures .............................................................................................................................. 1
Enclosure 1 ........................................................................................................................ 1
Enclosure 2 ........................................................................................................................ 3
Enclosure 3 ........................................................................................................................ 6
Enclosure 4 ........................................................................................................................ 8
Enclosure 5 ........................................................................................................................ 9
Enclosure 6 ...................................................................................................................... 10
Enclosure 7 ...................................................................................................................... 11
Anna Katarzyna Plawecka October 30, 2015
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List of figures
Unless otherwise stated all illustrations / photographs are the work of the author
Figure 1: Eelgrass on the beach (Jensen, Tængemænd og vaskerpiger, 2012) ............................................... 11
Figure 2: Seaweed as a first fridge insulation (www.seagrassli.org) ............................................................... 11
Figure 3: Timeline showing history of seaweed used as building material ..................................................... 12
Figure 5: Seaweed roof of traditional Chinese house in Jiaodong Peninsula (www.usa.chinadaily.com) ....... 12
Figure 4: Chinese seaweed houses (www.duskyswondersite.com) ................................................................ 12
Figure 6: Construction of Chinese seaweed roof (Zhang, 2011) ...................................................................... 13
Figure 7: House with seaweed roof thatching at Læsø (Jensen, Tængemænd og vaskerpiger, 2012) ............ 13
Figure 8: Seaweed roof thatching at Læsø (Jensen, Tængemænd og vaskerpiger, 2012) ............................... 13
Figure 9: Women rolling the eelgrass (Jensen, Tængemænd og vaskerpiger, 2012) ...................................... 14
Figure 10: Process on constructing eelgrass roof (Jensen, Tængemænd og vaskerpiger, 2012) ..................... 15
Figure 11 : Half-finished seaweed roof. (Jensen, Tængemænd og vaskerpiger, 2012) ................................... 15
Figure 12: Seaweed house on Læsø nowadays. (Jensen, Tængemænd og vaskerpiger, 2012) ....................... 15
Figure 13: Seagrass moving in Netherlands around 1900 (Nienhuis, 2008) .................................................... 16
Figure 14: Table showing number of bales (36 kg each) transported through the sea from the Port of
Yarmouth to Boston (Wylle-Echeverria & Cox, 1999) ...................................................................................... 17
Figure 15: Cabot´s Quilt Leaflet (Cabot, 1928) ................................................................................................ 18
Figure 16: Workers gathering already dry eelgrass form the fields (around 1925) (Wylle-Echeverria & Cox,
1999)................................................................................................................................................................ 18
Figure 17 : Seaweed from Cabot´s Insulation Quilt (www.seagrassli.org) ...................................................... 19
Figure 18: Radio City Music Hall insulated by seaweed (www.seagrassli.org) ............................................... 19
Figure 19: Works on Kjeld Post Fårehus (www.tangtag.dk) ............................................................................ 20
Figure 20: Adriane´s House before renovation (www.tangtag.dk) ................................................................. 21
Figure 24: Adriane´s House after renovation (www.tangtag.dk) .................................................................... 21
Figure 22: Europa Nostra prize awarded to the triumvirate´s activity since 2007 (www.tangtag.dk) ............ 21
Figure 23: Seaweed bales transported by ship (www.tangtag.dk).................................................................. 21
Figure 24: Seaweed Bank (Jensen, Tængemænd og vaskerpiger, 2012) ......................................................... 22
Figure 25: Pictures form renovation of Adriane´s House showing step by step how to build the seaweed roof.
(Jensen, Tængemænd og vaskerpiger, 2012) .................................................................................................. 22
Figure 26: The modern seaweed house (Realdania Byg, 2013) ....................................................................... 25
Figure 27: External cladding made out of seaweed stuffed into kitting net (Realdania Byg, 2013)................ 25
Figure 28: Interior of the modern seaweed house (www.dezeen.com) ........................................................... 26
Figure 29: Wooden skeleton of the house during construction process (Realdania Byg, 2013) ...................... 27
Figure 30: Prefabricated wooden element filled with dried seaweed (Realdania Byg, 2013) ......................... 28
Figure 31: Filling the nets with dried seaweed. (Realdania Byg, 2013) ........................................................... 28
Figure 32: Process of upholstering interior cladding (Realdania Byg, 2013) ................................................... 28
Figure 33: Installation of Interior cladding (Realdania Byg, 2013) .................................................................. 29
Figure 34 : Adding the binder to the material ................................................................................................. 30
Figure 35: Material during production. ........................................................................................................... 30
Figure 36: Seaweed rolls (Enclosure 2) ............................................................................................................ 31
Figure 37: Seaweed mats (Enclosure 2) ........................................................................................................... 31
Figure 38: Ridge finish out of seaweed mats (Enclosure 4) ............................................................................. 31
Figure 39: Ridge finish out of seaweed roll with seaweed mats on the sides and loose eelgrass in the middle.
(Enclosure 4) .................................................................................................................................................... 32
Anna Katarzyna Plawecka October 30, 2015
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Figure 40: Neptune Balls (www.fraunhofer.de)............................................................................................... 32
Figure 41: Installation of seaweed insulation produced by Neptutherm. (www.neptutherm.com) ................ 33
Figure 42: Old and new seaweed mat (Enclosure 4)........................................................................................ 36
Anna Katarzyna Plawecka October 30, 2015
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1. Introduction with problem formulation
1.1. Problem background information and presentation of the subject
This report is a part of a final examination for the Bachelor of Architectural
Technology and Construction Management education at VIA University College. The
choice of topic is inspired by growing need of finding more sustainable and
environmentally friendly materials in modern building industry. The answer for this
need can be new biological insulation materials, and seaweed is one of the most
promising one. The report will investigate into history of seaweed used as building
material, elaborate on its properties and research into use of seaweed in modern
design, including production and construction methods, aspects of esthetic and
sustainability.
1.2. Reasons for choice of the subject – personal relevance
The choice of the topic is inspired by personal interest in sustainable and
environmentally friendly materials. I believe that the future of architecture is the
design based on local, long-lasting resources which do not harm the environment.
Therefore the idea of using seaweed as an insulation material caught my attention
and I would like to research into possibilities of integrating it into modern design.
1.3. Problem statement
The problem in building industry of our times is that even though there is more and
more sustainable building materials discovered, architects and engineers are afraid of
implementing them, because they are not convinced about their quality. New
biological insulation materials, among which figures seaweed, are more subject of
jokes rather than being taken in account as a proposal for insulating buildings. This
attitude can be changed only by investigating into the topic and researching about the
materials. This report is going to focus on seaweed, which is really promising
insulation material, but most of the architects and construction architects still would
not even risk thinking about actually using it in theirs projects, because in their
opinion it is not really good material to use. Or is it? It is obviously hard to judge
unknown, and that it how the main research question emerged:
o Is it possible to use in building industry simple seaweed considered as sea
waste, learn from its rich history and transform it into modern, sustainable
material standing up to 21st
century esthetic and technical demands, or will it
always stay on the carts of history just as an old, good fairy tale?
Anna Katarzyna Plawecka October 30, 2015
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1.4. Delimitation
This report will focus on history, properties, esthetics, modern design, production as
well as construction of seaweed insulation. This report is not going into details of any
other purpose of seaweed than insulating material for buildings. Furthermore, the
report will keep to commonly used terms in building industry and do not stick strictly
to proper biological terms.
1.5. Choice of theoretical basis and sources of empirical data
The report will be based on Building Regulations 2010, books, articles, websites as
well as interviews, seaweed workshop and an amateur experiment as sources of
empirical data.
1.6. Choice of research methodology and empirical data
The report will be based mostly on secondary data-books and articles. (Primary data
in form of interviews, event participation and an experiment will also be included).
The report will analyze mostly qualitative data (however, quantitative data will also be
included).
1.7. Choice of working method
Frist of all I have researched all information I could find about seaweed used in the
building industry. Then I started reading obtained materials, from time to time finding
some new article / book relevant to the research. After the general research I decided
what exactly my report should contain, I got it approved by supervisor, and I started
detail research on particular sections. Along with detail research I began writing the
report. During the process I have visited Advance Nonwoven, company producing
seaweed insulation mats, and interviewed Flemming Werk. After that I participated
partly in the workshop about using seaweed mats as a ridge finish for roofs thatched
with straw. From there comes the interview with Bodil E.Pallesen. Then I added
obtained information to the report and changed some of the existing parts of the
report. In the end I checked everything again, read it through and handed it in.
Anna Katarzyna Plawecka October 30, 2015
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2. Closer look on the seaweed
For a human of XXI century seaweed is mostly a sea waste,
disturbing swimming and general holiday experience. It is
something unpleasant, unwanted and annoying. But it had not
always been like that. Seaweed has a rich history in many areas of
our lives, a lot of them the ordinary man in the street would
never imagine. It also plays crucial role in the sea. It provides
shelter and food for many plan and animals; it can also improve
water quality. (www.mesa.edu.au)
Seri Indians of Mexico considered seagrass really important material. They were using
seagrass almost everywhere: as a source of food, material to smoke the deer meat as well
as to make either baskets or toys for children. Furthermore, they did also use seagrass to
produce a medicine to treat diarrhea. Seagrass played so big role in their culture, that it
even influenced the name of the month: April in their local language was called “the
month when the eelgrass is mature”. (www.seagrassli.org)
Moreover, through the ages seaweed had been used (and in some cases is still used) as a
soil fertilizer and conditioner as well as mulch, stock supplement and above all as a fill in
pillows and matrasses as well as upholstery. Furthermore, it can be used also to make
furniture, mats, ropes or even shoes (www.seagrassli.org;
www.mesa.edu.au)
Getting closer to the insulating properties of the material, it is
reported that Frigidaire´s first refrigerator produced in 1919
contained eelgrass insulation in the construction, but had to be
replaced by corkboard in the mid 20´s due to smell issue.
(www.seagrassli.org)
To sum up, seaweed is an incredible material with many possible applications in wide
array of different fields. It was proven by history that this material can more than just lie
on the beach and disturb dream holiday. The next chapters show that seaweed had been
equally valuable material for building industry and definitely deserves more than just
being called a sea waste.
Figure 1: Eelgrass on the beach
(Jensen, Tængemænd og
vaskerpiger, 2012)
Figure 2: Seaweed as a first fridge
insulation (www.seagrassli.org)
Anna Katarzyna Plawecka October 30, 2015
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3. History of seaweed in building industry
The idea of using seaweed as insulating material is not new. It was used through the ages
in many different parts of the world. However, the technique and the way it was used is
not precisely the same. This chapter will analyze circumstances and reasons of using
seaweed as a building material, methods of gathering and construction solutions, and in
the end cause of its disappearing.
3.1. China
Sources point on China as the place where seaweed
was used in building industry for the first time. Some
publications also speculate usage of seaweed in
Europe at that time, but because of lack of evidence it
is not possible to confirm this hypothesis. The first
“seaweed houses” were mainly scattered over
Jiaodong Peninsula (costal area of Shandong Province)
and they started appearing in early stage of Shang and
Zhou Dynasties, which dates back to 1600 B.C. The
houses were really simple at the beginning, but with
the time the technique of construction gradually
improved. The seaweed houses were a perfect
solution for temperature monsoon climate – their two
meter thick stonewall and seaweed roof was natural
thermal insulator and kept houses warm in winter
and dry in summer. The houses started disappearing
in XX century partly because of illness which
significantly decreased the seaweed population.
(www.china.org)
1600 B.C.
Traditional Seaweed Houses
China
Xlll century
Denmark Læsø
XVII century
First settlers on Long
Island (USA)
1890s -Cabot`s
Quilt Insulation
The Netherlands
1907-1960
Gathering in USA
1930s -seagrass disease
1930Guildfords
Limited, Nova Scotia
Figure 5: Chinese seaweed houses
(www.duskyswondersite.com)
Figure 4: Seaweed roof of traditional
Chinese house in Jiaodong Peninsula
(www.usa.chinadaily.com)
Figure 3: Timeline showing history of seaweed used as building material
Anna Katarzyna Plawecka October 30, 2015
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Construction solutions
According to the traditional working methods,
seaweed should be placed directly on the battens
and cover the timber skeleton in turns. A layer of
seaweed was 100 mm thicker at the ridge in order
to enlarge the roof slope and facilitate drainage.
Each layer of seaweed was followed by wooden
frame in order to prevent seaweed being blown
away form the roof. Wooden frame created also an
air gap between seaweed layers, which was
lightening, insulating and sealing the whole
construction. Every wooden frame was fixed and
linked with timber frame underneath. This
construction process requires tree or four people to
work constantly 10 days. All work was done by
hand. (Zhang, 2011) (www.chinadaily.com)
3.2. Denmark
It was actually one specific part of Denmark, where
the special method of building seaweed roofs was
invented. The method of building is now an
exceptional part of cultural heritage of Denmark and
catches attention all over the world. This place is an
island on the north of Denmark, called Læsø.
First seaweed houses started appearing there in XIII
century, after the Viking era, when first inhabitants
arrived on Læsø. The island was rich in salt, and they
were attracted by possibilities of harvesting salt.
Unfortunately, besides high salt concentration the
island was poor in building materials known at that
time – there were no lakes with reed and the soil
type did not give much hope for farming. However,
the island was rich in forests and plenty of eelgrass
lying on the coast. That is probably why the first
inhabitants of Læsø, being used to straw thatched
roofs, decided to replace missing building material
Figure 6: Construction of Chinese seaweed
roof (Zhang, 2011)
Figure 7: House with seaweed roof thatching at
Læsø (Jensen, Tængemænd og vaskerpiger,
2012)
Figure 8: Seaweed roof thatching at Læsø
(Jensen, Tængemænd og vaskerpiger, 2012)
Anna Katarzyna Plawecka October 30, 2015
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with eelgrass. (Jensen, Naturens eget tag, 2014)
According to Jensen seaweed houses existed also on Halland in Sweden and on two
islands in Horsens Fjord – Endelave and Hjarnø – but they do not represent as important
cultural heritage as the unique houses from Læsø. The reason of that is the fact that they
were constructed just due to lack of other resources and the technique of building the
seaweed roofs was not exceptional. (Jensen, Tængemænd og vaskerpiger, 2012)
Gathering methods
Seaweed was collected from the beach with horse carriages and placed on the fields to
dry out. There seaweed was drying for around 14 days, after that it was collected again
and stored. (Jensen, Naturens eget tag, 2014)
Construction solutions
The first seaweed roofs were easy and fast to build and did not require deep construction
knowledge.Loose eelgrass, a type of seaweed used at Læsø, was just placed on top of the
roof skeleton and fixed to it in many different combinations, which yet did not resemble
the method of fixing used for constructing straw thatched roofs at that time. This simple
method had one big disadvantage: loose eelgrass was heavy, which created a challenge of
constructing load-bearing structure strong enough to withstand the weight of seaweed.
Roofs made out of loose seaweed were being constructed trough following around four
up to five hundred years. (Jensen, Naturens eget tag, 2014)
During these centuries many things happen. Production of salt led to deforestation of the
island, and despite of many tries the salt business ended. Many people decided to move
out from the island and Læsø became deserted. That became a reason of really
characteristic division of work which appeared around XVIII century. Men were mostly
sailors, and when they were back on the island they were either fishing or collecting
timber form ship wrecks around the island. On the Contrary, women had to take care of
the fields, family and house, and that included also construction of buildings. (Jensen,
Naturens eget tag, 2014)
In the construction process were involved almost all
women from the island. That means that at the “building
site” could be even 100 people in one day. Women
working with the eelgrass were called “vaskerkoner” or
“vaskerpiger”. As it is shown in figure 9 and 10, women
were working in pairs, rolling and turning the piece of
eelgrass to obtain the sausage-like shape (“vasker” in
Danish). Seagrass rolls were tied to the lowest timber rack
Figure 9: Women rolling the eelgrass
(Jensen, Tængemænd og vaskerpiger,
2012)
Anna Katarzyna Plawecka October 30, 2015
15
in the roof, so the rest of the seaweed can bear on them.
The work was managed by a man, who was experienced in
carpentry. He was the one tying seaweed to the battens
and making sure the roof had the right thickness and
airtightness. Even though it
may be surprising, that the
man was the one leading
the work, everything has its
explanation. The timber
used for the construction was coming from ship wrecks and
only the carpenter could estimate if each piece of timber is
strong enough in order to use it in the construction.
(Jensen, Naturens eget tag, 2014)
What happened with seaweed houses at Læsø
The last fully thatched roof was built in 1870s. Later on roofs
were only renovated, but it did not last long. Eelgrass was
decimated by fungus illness in 1930s, which led to the end of
seaweed era on Læsø. In XIX century there was around 230
seaweed houses at Læsø, in 1970s the number dropped to
90.
In 1951 women from Læsø were invented by Danish museum
to thatch a new eelgrass roof. The process was recorded and
photographed and is now the main source of information
about the construction solutions that are now unique cultural
heritage of Læsø Island.
In 1955 the Læsø´s museum opened. It was located in the old building which eelgrass
thatched roof renovated with 40 tons of seaweed bought form Kallehave Tang-Export
form Zealand, close to both Møn and Bogø Islands. In the best period the company was
employing around 40 people and exporting seaweed to many countries for insulating
purposes as well as matrasses filling. Unfortunately the company closed in 1959 and for
some decades the world forgot about eelgrass.
Nowadays there are around 20 houses left, most of them being forgotten and slowly
falling into decay, until seaweed return on the island in 2000s, which will be described in
next chapter. (Jensen, Naturens eget tag, 2014)
Figure 10: Process on constructing
eelgrass roof (Jensen, Tængemænd og
vaskerpiger, 2012)
Figure 11 : Half-finished seaweed
roof. (Jensen, Tængemænd og
vaskerpiger, 2012)
Figure 12: Seaweed house on Læsø
nowadays. (Jensen, Tængemænd og
vaskerpiger, 2012)
Anna Katarzyna Plawecka October 30, 2015
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Figure 13: Seagrass moving in Netherlands
around 1900 (Nienhuis, 2008)
3.3. Netherlands
In Netherlands the first use of seagrass is dated back to 14th
century, where it was used to
reinforce levees on Wieringen Island in North Holland. The island was frequently flooded
and that is why levees were in high need. According to Nienhuis “the dried weed had the
advantage that it compacted to a hard almost stone-like mass that was rather resistant to
wave attack”. (Nienhuis, 2008, p. 442) Later on, in 16th
century, eelgrass together with
wood was used to build 2 m high dyke. Dyke`s remains which survived to our times are
the proof of exceptional durability of eelgrass. Nienhuis also mentions that seaweed in
Northern Europe was used to thatching roofs. (Nienhuis, 2008)
More information is available about 18th
and 19th
century. Seaweed was gathered either
directly from the sea or form tidal flats, dried and used as roof thatching and insulation.
During renovation of castle Waardenburg on river Waal in 2007 it was revealed that part
of the ceiling construction contained layer of eelgrass in perfect conditions, even though
it is assumed that it lied there at least 150 years. (Nienhuis, 2008)
19th
century and the industrial gathering
In 19th
century seaweed became popular building material and a source of main income
for many fishers. In 1826 the first industrial moving of seaweed started. This seaweed,
gathered directly from the water, was better quality than the one collected on the beach.
It was gathered by people standing in half-tide water who moved the eelgrass with an
elongated scythe, gathered it to the net and then speeded it to dry partially on the field.
After that seaweed was staying in freshwater ditches for certain amount of time in order
to take the salt out of the plant, then dried again. In the end seagrass was transported to
warehouses and pressed in special weed-press into bales ready for shipment. (Nienhuis,
2008)
The end of seaweed business
Due to the construction of Closure Dike (major
causeway in the Netherlands) in 1920s tidal
currents and patterns of sedimentation in
Wadden Sea changed. It resulted in destroying
seaweed beds, which never recovered. This led to
an end of seaweed gatherings in Netherlands.
(Nienhuis, 2008)
Anna Katarzyna Plawecka October 30, 2015
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3.4. USA
In XVII century early settlers arrived on Long Island in North America. It is documented,
that they were using eelgrass as an insulating material for homes. They were making so-
called “banking up” which consisted of layering outer walls of the buildings with loose,
dry leaves of Zostera Marina. The early settlers were also using Zostera Marina to fill up
various air gaps in the construction. In the result humans and animals were protected
from cold in winter and warmth in summer. Eelgrass was used as well as a bedding
material for livestock and mulch for gardens. The first settlers of North America were
gathering Zostera Marina for non- commercial, private use. (Moe, 2014) (Wylle-
Echeverria & Cox, 1999)
The example of building from those times is Old Pierce House in Dorchester,
Massachusetts in New England, build in 1683. During renovation works in 1893 dried
eelgrass was found between timbers framing of the structure. It might be that the
eelgrass used in the construction caught attention of Samuel Cabot, who at that time
came up with the idea of using seaweed as heat and sound insulating product, known as
Cabot’s Quilt insulation. That is also when the commercial gathering of seaweed started.
The house stands today. (Moe, 2014) (Wylle-Echeverria & Cox, 1999)
Yarmouth County was the place, where early
commercial gathering took place, and everything was
driven by manufacture of a seagrass quilt in Boston,
Massachusetts, USA. The gatherings did not require
big capital, because participants usually were farmers
or fishers and they could use equipment they
possessed. The big advantage was the time of
gathering (late July-October) which did not conflict
with farming or fishing time.
Then seagrass was first purchased exclusively by
Samuel Cabot Insulation Quilt, and after that also by
another company, Guildfords Limited from Dartmouth
in Nova Scotia. Data extracted form newspapers form
years 1907-1931 shows, that from 102 bales in year
1907 the production reached 12854 bales in 1929
(Figure 14). Each bale weighted approximately 36 kg.,
which means, that in 1929 almost 463 tons of seagrass
was produced. The business expanded so much, that
Figure 14: Table showing number of bales (36
kg each) transported through the sea from the
Port of Yarmouth to Boston (Wylle-Echeverria
& Cox, 1999)
Anna Katarzyna Plawecka October 30, 2015
18
Samuel Cabot`s company started to import seagrass form other countries, such as
Germany or Netherlands. Even the famous Titanic had some Dutch eelgrass cargo on
board. (Nienhuis, 2008)
In early 1930s the disease significantly reduced or
eliminated the population of Zostera Marina and
number of bales produced dropped significantly. It
prevented gatherings in Yarmouth County until 1939
and forced companies to import seagrass form River
Herbert in northern Nova Scotia and form Germany.
However, due to Word War II and lack of sufficient
seagrass resources in America the production of
seaweed insulation stopped. Guildfords limited tried to
continue production in 1950s, after recovering seagrass
form disease, but in result of advancement of other
insulation materials such as fiberglass and other
synthetic fiber products it did not succeed and the
commercial gatherings of eelgrass in United States were suspended in early 1960s.
(Wylle-Echeverria & Cox, 1999)
Gathering
The specific thing about the Yarmouth County was the 75 m long rock wall built in order
to capture seagrass before it will reach the coast. The eelgrass was forked form the wall
and placed on the ox carts. In other parts of Yarmouth County the leaves were captured
directly from the water or from the rocks. Then it was spread on the freshly moved hay
fields to dry and turned from time to time. When eelgrass was thoroughly dry, it was
transported to one of fourteen collection shed owned by Samuel Cabot. The sheds were
equipped in two types of balers. One was an iron hay baler and another wooden hand
press. Ready bales were stored until shipped to Boston. (Wylle-Echeverria & Cox, 1999)
Guildfords Limited used to gather seaweed in exactly the same way, with the difference
of transporting loose seagrass rather than baled leaves. (Wylle-Echeverria & Cox, 1999)
Figure 15: Cabot´s Quilt Leaflet
(Cabot, 1928)
Figure 16: Workers gathering already dry eelgrass form the fields (around 1925)
(Wylle-Echeverria & Cox, 1999)
Anna Katarzyna Plawecka October 30, 2015
19
Material description
Cabot`s Quilt Insulation, popularly called just Cabot`s
Quilt, was a material made by stitching layers of dried
eelgrass in various thickness between heavy Kraft paper.
It was available in three variations: single-ply (80 mm) for
single-family houses, double-ply (127 mm) for additional
sound insulation and asbestos single or double-ply
(covered with asbestos instead of paperboard). Later
other varieties became available, ending up in eight
different products. Cabot`s Quilt was used for wide array
of building types, from family houses, through apartment
buildings, offices, schools and lecture halls up to hospitals
and warehouses on the territories United States, Canada
and Great Britain, Australia, New Zealand, Sweden,
Finland, Holland and Argentine Republic. (Moe, 2014)
Many buildings in New York built at that time, including
Carnegie Hall, Radio City Music Hall and Rockefeller
Center were insulated by Cabot`s Quilt due to its brilliant
sound properties. (Wylle-Echeverria & Cox, 1999)
(www.seagrassli.org)
Construction solutions
Enclose 2 contains Cabot`s Quilt leaflet with technical details of construction solutions for
either new or existing buildings. Even though the insulation solutions are not perfect form
nowadays point of view, brochure like this one encouraged architects to start using
insulation in the construction. (Moe, 2014)
3.5. Part conclusion
We can learn a lot from the rich history of seaweed in building industry. It has been
proven, that seaweed is a strong, durable material, with good thermal insulation
properties. Examples of Chinese and Læsø`s seaweed houses show, that it can be used as
a long-lasting roof thatching which can withstand difficult weather conditions. Also
examples of Netherlands and America exhibit exceptional lifespan of seaweed. The
Cabot`s Quilt Insulation proved that seaweed used as sound and thermal insulating mat is
easy to install and good quality product which can be manufactured on large scale.
Comparing gathering methods it is clear that the seaweed gathered directly from the
water is a lot better quality than the one collected form the beach. The threating
Figure 17 : Seaweed from Cabot´s
Insulation Quilt (www.seagrassli.org)
Figure 18: Radio City Music Hall
insulated by seaweed
(www.seagrassli.org)
Anna Katarzyna Plawecka October 30, 2015
20
methods are really similar in all the countries, only Netherlands stands aside with their
method of desalting seaweed until it is thoroughly dry, but since there is not much
information available we cannot assess how much it changes seaweeds properties and
lifespan.
According to construction methods, it is hard to examine whether loose seaweed or
seaweed pressed in bales has better insulating properties. Generally speaking it also
depends on where the material should be used. Seaweed mats are of course easier to
work with, but they also require more processing than loose seaweed.
All in all, the seaweed`s rich history in building industry gives a lot of possibilities to build
on. The past of seaweed can become a good starting point in order to create new ideas of
applying seaweed into modern building industry.
4. The seaweed triumvirate
The history of seaweed did not end in XX century, it just stayed forgotten until the
initiative started in the first decade of 2000s by “Seaweed Triumvirate” at Danish island
Læsø. The triumvirate consisted of two inhabitants of Læsø, farmer Henning Johansen
and businessmen Poul Christensen, together with architect Marcelle Meier.
The triumvirate was well matched. Henning Johansen was roof thatcher at Læsø who
knew how to work with eelgrass, Poul Christensen was his neighbor who succeeded in
obtaining funds for Læsø´s salt production, and Marcelle Maier had strong theoretical
knowledge about seaweed due to the fact that her master theses were about unique
seaweed thatched roofs. In the other words, they had all type of experience needed:
practical, theoretical and economical. (Jensen, Naturens eget tag, 2014)
4.1. Triumvirate´s activity
The triumvirate, together with Rune Ottesen, a museum´s thatcher
trainee, began the work form thatching the roof of newly built Kjeld
Post Fårehus. The project was financed by Realdania and brought
first experiences of working with seaweed. The first three tons of
material delivered from Bogø did not stand up to quality standards,
but the next transport containing seaweed just after harvest was
totally fine. That was the lesson, that quality of seaweed matters:
“We have all learned that seaweed is not just seaweed”
commented Henning Johansen, initiator of the triumvirate. (Jensen,
Naturens eget tag, 2014, p. 163)
Figure 19: Works on Kjeld Post
Fårehus (www.tangtag.dk)
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21
After completing roof of Kjeld Post Fårehus the group continued
with small renovations of existing seaweed roofs, until the decision
was made that in 2011 the “Adirane´s House” should be
renovated thoroughly and a new seaweed roof should be
thatched. First time since 1870s a completely new eelgrass roof
was build. For these single construction 35 tons of seaweed was
used. (Jensen, Naturens eget tag, 2014)
In 2012 Realdania Byg purchased “Kaline´s house”, which is another
old seaweed house on Læsø, and renovated it. (Jensen, Naturens
eget tag, 2014)
In the same year the prestigious Europa-Nostra prize for Cultural
Heritage in category: Education, training and awareness rising was
awarded to the triumvirate´s activity since 2007, which included
establishment of Seaweed Bank and the plan of rescuing the last
existing seaweed houses in the world. General interest in seaweed
roofs grew, and that led to initiative of using this material in new,
modern ways. (Jensen, Naturens eget tag, 2014)
(www.tangtag.dk)
4.2. The gathering and Seaweed Bank idea
Seaweed is gathered and dried on two Danish islands, Møn and
Bogø, and then transported to Læsø. It should be gathered
immediately after appearing on the beach: “Seaweed should be
gathered form the beach and dried as soon as possible, the best in
the same day. It lies for a long time in warmth without any risk of
moisture, processes which are decomposing the fibers in seaweed
starts.” These are words of the farmer and seaweed fisher form
Møn, Ib Ungermand (Realdania Byg, 2013, p. 3)
Because eelgrass is a living plant, the harvest time is not constant,
and it depends a lot on the water condition. Some years waters may be rich in eelgrass,
some not. This infrequency in harvest time forces seaweed to be gathered when
possibility occurs, and that leads to costs of storing huge quantities of eelgrass for
unprecise amount of time. The solution for that is Seaweed Bank, which should always
have at least 100 tons of eelgrass on stock. (www.tangtag.dk)
Figure 23: Seaweed bales
transported by ship
(www.tangtag.dk)
Figure 22: Europa Nostra prize
awarded to the triumvirate´s
activity since 2007
(www.tangtag.dk)
Figure 21: Adriane´s House after
renovation (www.tangtag.dk)
Figure 20: Adriane´s House before
renovation (www.tangtag.dk)
Anna Katarzyna Plawecka October 30, 2015
22
The bank itself is not a cheap thing, but the idea caught the attention of the public and
many sponsors decided to donate money in order to help with establishment of such
seaweed storage. The role of the bank is to buy and sell
seaweed for each individual renovation project as well as to
take care of the process of registration and arrangement of
replacement of existing seaweed roofs so that the
possibilities of improving construction techniques and
working method are examined. The future aim is to
mechanize the construction process so that construction
period is shorter and working method is easier. The Bank tries also to change thatching
law in order to use seaweed as a material on a straw roof which would in that case
replace heather. (www.tangtag.dk)
Organization is said to be non-profit and the money from the seaweed sell are just for
covering the expenses of transportation and other costs of running the Bank. The
Seaweed Bank on Læsø is managed by Seaweed Triumvirate members. (www.tangtag.dk)
4.3. The construction methods
The construction method used by
Seaweed Triumvirate is based on
traditional Læsø´s technique of thatching
seaweed roofs with few modern
improvements. The starting point is a
good quality, well-dried eelgrass of
appropriate length. Another important
issue is accuracy in creating rolls out of
seaweed. The better they are made and
fastened to the battens, the longer the
roof will last. (Jensen, Tængemænd og
vaskerpiger, 2012)
Figure 25 shows how such a roof is built
step by step. The first step is to twist the
seaweed so the rolls are created. The
process is mechanized with the use of
electronic screwdriver on one side of the
seaweed roll and electronic machine built
by local electrician on the other side. The machine requires assistance of three men, but
Figure 24: Seaweed Bank (Jensen,
Tængemænd og vaskerpiger, 2012)
Figure 25: Pictures form renovation of Adriane´s House
showing step by step how to build the seaweed roof. (Jensen,
Tængemænd og vaskerpiger, 2012)
Anna Katarzyna Plawecka October 30, 2015
23
on the contrary the process is at least twice as fast as the traditional one. (Jensen,
Tængemænd og vaskerpiger, 2012)
After rolls are ready they have to be lifted by two men each and tied strong to the lowest
roof batten. Then space between the tied rolls is filled up with non-tied rolls. And the
process is continued until the three lowest racks are ready. They should be altogether
around 180 cm thick. (Jensen, Tængemænd og vaskerpiger, 2012)
Then the wooden skeleton of the roof is covered with fir, pine or spruce branches
preventing the seaweed to fall inside the house though gaps between battens. Finally,
loose seaweed is placed on the roof, filled in the gaps and stepped on in order to
strengthen the construction. On top of the seaweed is laid a turf ridge, which will blend
with seaweed after some time. (Jensen, Tængemænd og vaskerpiger, 2012)
(www.naturalhomes.org)
When the construction is finished roof requires few months so the seaweed falls a bit
down and the structure becomes more dense and strong. Then the openings for windows
and doors in the roof are cut using nowadays petrol-powered hedge trimmer. (Jensen,
Tængemænd og vaskerpiger, 2012)
After about one year roof changes the color to silvery grey, it´s structure becomes more
solid and plants starts growing on top of seaweed thatching. It is also the time when the
roof becomes waterproof. Even though the seaweed thatching is not initially airtight, its
thickness does not allow any water to penetrate through anyway and no damages occur
because of that reason. (www.naturalhomes.org)
4.4. Part Conclusion
Generally speaking Seaweed Triumvirate achieved a lot. The most important thing is that
it brought back to llife the forgotten tradition of thatching roof with seaweed. Many
houses were renvated and some new were build. Fruthermore, the Seaweed Bank was
established ensuring inhabitants and investors that the material will be always avaliable.
Last, but not least, the activity of Seaweed Triumvirate got noticed and awarded by
honourable price Europa-Nostra in 2012. All of these achievement made the island and
seaweed more known. On the other hand, the activity of Triumvirate, even though
excellent while repearing old seaweed roofs and maintaining tradition, did not improve
the working methods and old house outlook. If the material should be used in modern
buildings, the esthetics and building process also need to stand up to nowadays standads,
and Seaweeed´s triumvirate proposal did not fulfil these needs. However, they reminded
Anna Katarzyna Plawecka October 30, 2015
24
the world about valuable, old building material, which possibilities can reach far beyond
simple roof thatching.
5. The modern seaweed house
Restauration of traditional seaweed houses on Læsø and activity of Seaweed Triumvirate
have proven that seaweed plays its role as an insulator and roof thatching, but it was still
not clear, how the material could be use in contemporary design. Something had to be
changed, because not everybody fancies living in traditional seaweed house with few tons
of eelgrass used as a roof thatching. Therefore the idea of building the modern seaweed
houses emerged.
5.1. The challenge
Realdania Byg is a non-profit organization which has been supporting the activity of
Seaweed Triumvirate since the beginning. This organization founded the new roof of
“Kjeld Post Fårehus” and later on bought and then renovated the “Kaline´s house” in
2012. And it actually was the same organization, which have bought the land on Læsø
and decided to build a modern house made out of seaweed. (Ehmann, Klanten , &
Borges, 2014; Jensen, Naturens eget tag, 2014)
Realdania announced a competition in 2012 for designing a modern summerhouse on
Læsø. The new seaweed house was supposed to be mostly a material experiment, which
was an attempt to try out the same materials used in traditional seaweed houses, but in
new, modern ways. The project was supposed to be sustainable not only in
environmental aspect, but also in economical. In the other words, it was required, that
the cost of the building fits in the budget of any other summerhouse of similar size.
Furthermore, the house was supposed to stand just nearby freshly renovated “Kaline´s
House”, which meant, that its appearance has to match to traditional seaweed houses on
the island. (Realdania Byg, 2013)
The competition organized by Realdania Byg won Vandkunsten Tegnestue, Architectural
office from Copenhagen. They came up with the design of the house, which “combines
the traditional material with twenty-first century construction techniques,” as Jørgen
Søndermark from Realdania Byg summed it up (www.dezeen.com).
Indeed, the design of the house does not stand out form modern architectural norms,
even though the main material used for the construction is not that modern seaweed.
“We have used natural materials in the modern way, and we had luckily a client, that was
willing to experiment” says Søren Nielsen, architect maa from Vandkunsten Tegnestue
(Jensen, Naturens eget tag, 2014, p. 167)
Anna Katarzyna Plawecka October 30, 2015
25
The results of this experiment are quite impressive.
The house is built in simple, long traditional shape
characteristic to the island, with seaweed cladding
composed gently into the form. The Vandkunsten
Tegnestuen took care of details: the size of the
building, duo-pitched roof, or even East-West
orientation is matching perfectly with the Læsø´s
tradition as well as local planning restrictions, which
makes the house literally blend in the environment.
Only the small elements of design, beyond which
the most distinctive is seaweed external cladding, indicate the modernity of the project.
(Realdania Byg, 2013; Ehmann, Klanten , & Borges, 2014)
5.2. Esthetics
Seaweed is a challenging material for an architect, because it is completely opposite of
precision – it´s irregular, messy and unstructured. On the other hand, in the modern
architecture really important is precision. Lines should be straight and edges sharp. By
that architects create a rational and perfect world, which in real life is really hard to
achieve. For an average man perfection is something beyond his abilities, and it results in
less and less people actually believing in it. Understanding it in this way, the conclusion
can be that adding some softness to the building´s straight lines and sharp edges which
actually can make the building easier to relate to for people of our times, who are not
craving for perfection any more, but they still need some kind of balance in their lives.
(Realdania Byg, 2013)
Following this thought the architect maa Søren
Nielsen form Tegnestuen Vandkunsten cape up with
the idea of the modern seaweed house´s design. He
decided to find a balance between the softness the
material the perfection and proposed to use as
external cladding the cylindrically shaped nets filled
with eelgrass. Each building element was supposed to
have certain amount of cylinders installed inside the
wooden frame. In this way a structure of rhythmical
vertical and horizontal elements was created, and a softness and irregularity of the
seaweed was balanced with a precision of repetitive simple pattern. “The building
vibrates lively between abandon and discipline”, as Søren Nielsen had summed it up.
(Realdania Byg, 2013, p. 34)
Figure 26: The modern seaweed house
(Realdania Byg, 2013)
Figure 27: External cladding made out of
seaweed stuffed into kitting net (Realdania
Byg, 2013)
Anna Katarzyna Plawecka October 30, 2015
26
Interior design, despite its simple form, also brings some
novelty. The uncommon choice was a ceiling finish made out of
linen cloth stuffed with eelgrass. Upholster Brian Liebeck
admits: “To find a right fabric had been itself a challenge. Only
after checking at least hundred different fabric samples in
cooperation with the architects we came up with the final
solution. It is a light linen fabric, which can last up to twenty
years, if it is properly maintained.” (Realdania Byg, 2013, p. 5)
The architect´s initial idea was to install one unbroken piece of
cloth at the ceiling in order to create the impression of being in
the tent, but due to the necessity of prefabrication this idea could not be fully realized.
However, even though the element´s breaks are visible, the ceiling still gives incredible
impression of coziness, which does not appear so often in modern architectural design.
Another virtue of the internal cladding is its excellent acoustic properties, owing to either
eelgrass or soft linen textile. (Realdania Byg, 2013)
Wood is the second material significant in the modern seaweed house´s design. It
appears almost everywhere. Larch, pine or spruce battens are main part of house´s
construction. Furthermore, they appear in most of the finishes such as floors, internal
cladding or even kitchen table. But even though three matches perfectly as a background
for exterior seaweed cladding, it deserves also to be appreciated individually. Timber is
never the same, and despite of the fact that these unpredictable and unstructured
differences in wood grain and wood color can be challenging to the ones admiring
perfection, it hard not to enjoy the beauty of it. Wood is an amazing material, because it
changes with time and makes building alive. (Realdania Byg, 2013)
5.3. Sustainability
Jørgen Søndermark from Realdania Byg said : "By using seaweed in the construction, we
not only secure the continued supply of seaweed for use on the historic houses, we also
reintroduce a material to the modern building industry which is CO2-reducing,
environmentally friendly and sustainable in a broader sense." (www.dezeen.com)
Indeed, seaweed is a natural material of the sea, which can be gathered and processed
with remarkably little amount of energy. Together with wood, they both produce
negative carbon dioxide footprint and have a huge advantage towards other buildings in
energy consumption calculations just form the start. Furthermore, the building is said to
consume no more energy than 20 KWh per meter squared per year, which stands up to
highest energy requirements in Denmark and fulfils energy frame 2020. This is achieved
due to composition of many passive elements in the house, starting from high pitched
Figure 28: Interior of the modern
seaweed house (www.dezeen.com)
Anna Katarzyna Plawecka October 30, 2015
27
roof in order to maximize the passive solar heating through skylights, through airtight
construction, thick layer of insulation and triple-glazed windows, ending with mechanical
ventilation with heat recovery and heat pump. (Ehmann, Klanten , & Borges, 2014;
www.bygningsreglementet.dk)
Generally speaking, sustainability is becoming more and more important aspect of
modern building industry. Søren Nielsen describes it perfectly: “The modern seaweed
house on Læsø is not just a tale about innovative applications of a renewable material in a
distinctive place with a rather unusual buildings history. It is also a crystal ball, which
captures and enlightens many of the most vital problems the building industry is facing
today.” (Realdania Byg, 2013, p. 13)
5.4. Economy
The modern seaweed house can be considered sustainable not only environmentally, but
also economically. The goal of the project was to fit into budget of standard Danish
summerhouse of similar size, and due to prefabrication it managed to be fulfilled.
Moreover, owing to prefabrication the prize of the building fell according to the
estimations, and that allowed realizing more expensive ideas in the project, such as
upholstered ceilings or energy-saving installations. The price of the construction turned
out to be 2 million DKK excluding taxes. (Vandkunsten Tegnestuen; Ehmann, Klanten , &
Borges, 2014; Realdania Byg, 2013)
Furthermore, it is not required to maintain the seaweed elements of the house, and the
expected lifespan is comparable to similar house built with standard materials. (Ehmann,
Klanten , & Borges, 2014)
5.5. Construction
The modern seaweed house built with
prefabricated wooden element resting on
the wooden skeleton. The insulating
material of all elements, the same as
internal and external cladding of the house
is made out of seaweed. The decision of
prefabrication was taken due to financial
issues and really tight time schedule, and in result elements were produced in three
workshops in different parts of Denmark: one in Frederiksberg in Copenhagen, another
one in Kongerslev in Northern Denmark, and the last one on the Møn Island. (Realdania
Byg, 2013)
Figure 29: Wooden skeleton of the house during
construction process (Realdania Byg, 2013)
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The wooden skeleton of the house was produced in Kongerslev in Northern Denmark, and
then wooden modules were packed on a truck and shipped to Læsø. To transport all the
modules process needed to be repeated five times. After that the wooden skeleton was
mounted on pile foundations, which were chosen due to moist climate on Læsø in winter
time. (Realdania Byg, 2013)
The wooden floor, roof, and wall elements stuffed with
seaweed were a lot more challenging to work with. The
company was used to work with firm insulation materials
and dried seaweed was completely opposite of that. It had
to be separated from each other in order to obtain a loose
material. To be sure that the elements have sufficient u-
value loose seaweed needed to be weighted before placed
in the element. To that process a hanging butcher´s weight
was used. (Realdania Byg, 2013)
Even more complicated was working with exterior cladding. It was the task of the Praktisk
Service company form Møn Island. The seaweed was stuffed
into net made out of brown knitting wool. The net was
handmade, but it was knitted in the way, that it possible to
be industrialized in the future. The biggest challenge was
stuffing the seaweed into woolen “sleeves” to obtain an
equal thickness of the bolster on the whole length. It was
obtained by carefully filling in the dry eelgrass trough short
plastic pipe. The process required a lot of skill, but it
succeeded. (Realdania Byg, 2013)
There were two different types of external cladding. The roof bolsters were thicker and
softer. They were fixed to spruce rafters and then fasten to trusses. That is why their
needed to be 6 meters long. The wall bolsters should fit on the wall elements, so they
were shorter and harder. On one wall element could fit around 15 bolsters. (Realdania
Byg, 2013) (Ehmann, Klanten , & Borges, 2014)
To integrate the structure of the roof dense roofing felt was placed
between wooden roof elements and seaweed cladding. During the
time it is expected that as a part of natural process of weathering
the roof will become a habitat of plants and birds. (Ehmann,
Klanten , & Borges, 2014)
The interior cladding is another unconventional element of the
house. It is made out of panels upholstered with linen fabric and Figure 32: Process of
upholstering interior cladding
(Realdania Byg, 2013)
Figure 30: Prefabricated wooden
element filled with dried seaweed
(Realdania Byg, 2013)
Figure 31: Filling the nets with dried
seaweed. (Realdania Byg, 2013)
Anna Katarzyna Plawecka October 30, 2015
29
stuffed with seaweed. Fortunately the technique was similar to the one used before
1960s to produce matrasses out of seaweed, so the process was not so new, it just
required a lot of time, since the method of upholstering did not change much since 1600s
and was mostly handmade. The panels 2,4 meter long and 0,6 meter wide were first filled
with dried seaweed, then upholstered first with fireproof layer, and at then with the
visible one made out of linen. (Realdania Byg, 2013)
Even though the work is mostly handmade, the precise sizes of panels could not be
possible to predict if not advanced architectural 3D
software, especially while talking about the panels at
the ridge or around skylights. The wooden panels
were manufactures with CNC cutting machine.
(Realdania Byg, 2013)
The expected lifespan of the linen fabric is around 20
years, if it will be maintained correctly and not
exposed too much to the sunshine. (Realdania Byg,
2013)
5.6. The future
The project on Læsø has shown the possibilities of sustainable, environmentally-friendly
building industry. "The seaweed houses on Læsø are physical testimony to the culture
and the life that have characterized the building tradition on the island for centuries,"
said Realdania Byg director Peter Cederfeld. "It is our hope that others will embrace the
experiences from this project and develop the ideas even further." (www.dezeen.com)
5.7. Part conclusion
The example of the modern seaweed house on Læsø has shown that it is possible to use a
really old building material such as seaweed and adjust it to today´s standards of esthetics
and functionality. Furthermore, the project had proven that it is possible to build a
seaweed house with the same budget and time schedule as similar-size building made out
of standard materials, but with the significant difference in carbon dioxide footprint.
Moreover, the techniques of prefabrication used in the project (or the possibility of
mechanizing the work in case of woolen knitting nets production) create the way to lower
the price even more due to rise of demand of the product. In the end, the project got
interest of many people all over the world and turned the attention on Læsø and its
unique building techniques.
Figure 33: Installation of Interior cladding
(Realdania Byg, 2013)
Anna Katarzyna Plawecka October 30, 2015
30
6. Production of seaweed insulation and its application
This chapter will describe the various modern methods of producing seaweed insulation
material and evaluate the sustainability of each of them as well as analyze the efficiency
of each method and the level of difficulty while working with the ready product.
6.1. Seaweed insulation mats
Seaweed insulation mats are produced by Advance nonwoven, which is an international
company using natural fibers, waste or recycled materials to production various purposes
mats. The company is using unique CRAFT technology which is yet the only one on the
world, according to the interview with Flemming Werk form Advance Nonwoven
(Enclosure 2)
Source of seaweed
According to the interview with Flemming Werk form Advance Nonwoven (Enclosure 2)
seaweed is gathered on Bogø Island and transported to the company´s production hall in
Roende in Northern Denmark.
Production Method
Flemming Werk from Advance Nonwoven A/S explains the
exceptional production process as following:
“The raw material first goes through hammer mill, and goes
through a fiberizer and into storage boxes (hopper feeder and
weighing system) and then the binder is added to the material
mixed in “mixer.” After that the material is going through the
patented CAFT technology machine which creates desired
density and thickness of the mat. Then the mat goes to the
oven where the heat is used to bond the fibers. In the end mat is cooled down, cut into
required sizes, winded or stacked and packed, wrapped.” (Enclosure 2)
Sustainability aspect
According to the interview with Flemming Werk form Advance
Nonwoven (Enclosure 2) the technique of producing seaweed
mats or mats form any other natural fibers as well as recycled
materials and waste can be considered really sustainable and
futuristic. The company is able to reuse wide array of materials
until the point that fibers are too short to be reused, which
basically means that the only thing that remains form the
material is a bit of dust. Additionally, despite consuming the
Figure 34 : Adding the binder to
the material
Figure 35: Material during
production.
Anna Katarzyna Plawecka October 30, 2015
31
fuel and energy the machines do not pollute the atmosphere, due to installation of the
special Co2 filters.
Installation of the insulation
Since the product is still at the testing stage, no certain construction method had been
developed. However, the seaweed mats are consistent in structure and can be produced
in various sizes and forms (see figures 36 and 37), so there is variety of applications
available. Generally speaking, seaweed mats has a potential of being used as insulating
material in the form we are used to. In other words, they can replace standard, inorganic
materials such as mineral wool or polystyrene and be placed in traditional way as
insulation inside wall, roof or storey partition construction.
Furthermore, the project carried out in collaboration between Henning Johansen, Læsø
Seaweed Bank, Advance Nonwoven and AgroTech and the support of MUDP (Danish
Environmental Technology and Demonstration Department under the Environmental
Protection Agency) is researching weather seaweed mats can be used as a ridge finish on
the straw roofs. The project started 1st
of January 2015 and is expected to be finished 30th
of September 2016. (Enclosure 4)
The project is examining whether seaweed mats are better solution of straw roof ridge
finish in comparison with existing ones. The new material is expected to have longer
lifespan be easier to work with. In addition, the seaweed is famous of its poor
flammability, which would be an advantage.
The project is also researching into the best construction
method of building up the seaweed ridge. During the workshop,
which took place on 23th October 2015(Enclosure 4), various
solutions had been tested.
The initial idea was to place seaweed mat rule on the ridge,
with the roofing felt on one side and without on the other side,
and fix it with a metal net. However, thatchers decided to try
Figure 37: Seaweed mats (Enclosure 2) Figure 36: Seaweed rolls (Enclosure 2)
Figure 38: Ridge finish out of
seaweed mats (Enclosure 4)
Anna Katarzyna Plawecka October 30, 2015
32
also other solutions. On the connection between two parts of the roof on 90 degrees
angle the mats had been placed on one another with an overlap of around 100 mm. Each
mat had a size of 120 x 140 mm (see figure 38).
On the other side of the roof, due to esthetics reason, seaweed
rule with the roofing felt underlay was covered from two sides
by seaweed mats. In the gap between the mats dry eelgrass was
placed and on top of it another seaweed mat was installed.
(Figure 39).
Workshop had experimental character and allowed thatchers to
try the material in many different ways. All the work was
managed by Henning Johansen and Bodil Pallesen.
(www.agrotech.dk)
6.2. Neptune Balls
This type of seaweed is endemic to the Mediterranean Basin and it is used for insulation
production by Neptutherm® in Germany.
Gathering Method
Seaweed is gathered manually in Albania and Tunisia. According to the manufacturer of
Posidonia oceanica insulation in Tunisia work is carried out by large amount of women
and it takes 7 full days for 30 women in order to load one full truck of seaweed.
(www.neptutherm.com)
Transportation Method
Loose seaweed is transported by either ship or train. Only in case of lack of other choice
the trucks are used. (www.neptutherm.com)
Production Method
The most important part of production is removing the adhesive sand form the seagrass,
which is not easy at all. Additionally, individual fibers often catch on either each other or
surrounding and quickly form new clumps during the process of production as well as
while already blown into the construction.
However, There had been invented a way how to solve these problems.
According to Dr. Gudrun Gräbe form Fraunhofer Institute “Shaking the
Neptune balls proved the best way of making sure we end up with fibers
that are as long as possible and free of sand.” (www.cordis.europa.eu)
That means that Neptune balls are shaken until all the sand is
Figure 39: Ridge finish out of
seaweed roll with seaweed mats
on the sides and loose eelgrass in
the middle. (Enclosure 4)
Figure 40: Neptune Balls
(www.fraunhofer.de)
Anna Katarzyna Plawecka October 30, 2015
33
removed and the fibers are acquired. The seagrass fibers are delivered to cutting mills,
where they are cut in 1,5 – 2 cm pieces and packed into plastic bags.
(www.cordis.europa.eu; www.neptutherm.com)
Sustainability aspect
Neptune balls insulation is said to be really environmentally friendly product. The
production process does not require much energy, since the seagrass is gathered
manually and transported mostly by sea and road. That all makes Life Cycle Assessment
looks really promising. The manufacturer claims that the production of Posidonia
Oceanica insulation requires “up to 50 times less primary energy throughout the sourcing
and manufacturing process” in comparison with conventional insulating materials such as
grass, mineral wool, polystyrene or polyurethane foams and even wood fibers.
(www.neptutherm.com)
Additionally, according to eco-INSTITUTE in Cologne seaweed is 100 percent organic
material entirely free of extraneous or toxic matter and it is said to be particularly suitable
for allergy sufferers. (www.fraunhofer.de)
Installation of the insulation
The insulation can be installed either by professionals or directly by the client. The
difficulty level is said to be easy. The insulation can be filled into cavities in roof
construction, ceilings and walls and afterwards packed tightly by hands. In case of hard to
reach places the insulation is blown by a machine. (www.fraunhofer.de)
Figure 41: Installation of seaweed insulation produced by Neptutherm. (www.neptutherm.com)
6.3. Part conclusions
To sup up, even though both production methods seem really different form each other,
some principles still stay the same. However, while Neptutherm stops at chopping pure
seagrass into smaller fibers, Advance Nonwoven goes a step forward and owning to its
unique CRAFT technology is able to create a consistent product similar to the one we
know. These two different forms of the insulation bring different possibilities of usage-
one can be easier to work with in some cases, another in others. However, both materials
are 100% natural, sustainable and really promising.
Anna Katarzyna Plawecka October 30, 2015
34
7. Properties of seaweed
Even though the rich history of seaweed in building industry is pretty impressive, the
biggest question is still unanswered. Obviously, if seaweed is supposed to be used as
insulating material, it should also insulate and fulfill all the other demands insulating
materials nowadays has to fulfil. However, since the material is not fully introduced to the
market, it is impossible to define all the properties precisely. This chapter´s aim is
therefore to gather all available data concerning most important seaweed properties and
try to get the general overview.
7.1. Thermal conductivity
One of the most important values of insulation material is its ability to insulate. Therefore
thermal conductivity is the property, this chapter will start form. Seaweed has really good
insulating and heat holding capacity appreciated for centuries. According to Jørgen
Søndermark “120 mm of seaweed insulation equals 100 mm of modern mineral wool
insulation” (Realdania Byg, 2013, p. 53) Adding it to that the fact that seaweed is a
natural, sustainable product, it creates a certain competitiveness of seaweed on the
market of insulating materials. Especially, if the subject of comparison would be carbon
dioxide footprint - then seaweed insulation has not many other materials to be compared
to.
7.2. Acoustic properties
Together with good thermal insulating properties come exceptional sound insulating
properties. Cabot`s Quilt produced in United Stated before second world war was
advertised as “as efficient an insulator for sound-deadening as it is for heat and cold”.
(Cabot, 1928) That is probably why Radio City Music Hall in New York was insulated with
Cabot’s Quilt Insulation at that time (www.seagrassli.org). Even though we cannot base
on any nowadays scientific research, the opinions about seaweed houses are confirming
the hypothesis. According to Jørgen Søndermark from Realdania Byg seaweed has
“remarkable acoustic properties” and “this creates surprisingly comfortable rooms.”
(www.dezeen.com) In other words, seaweed has a great potential not only as a heat
insulator, but also as a sound insulator, which widens the possibilities of using seaweed in
building industry in general.
7.3. Reaction to fire
If the seaweed is such a good thermal and sound insulator, can it also insulate against
fire? This question is not that easy to answer. Nowadays a lot of attention is turned to
security against fire; therefore material´s fire-redundant properties are valued really high.
Seaweed, owning to slat content, is considered to be a material that does not burn.
Anna Katarzyna Plawecka October 30, 2015
35
However, even though many publications are expressing their amazement towards
unique fire-redundant properties of the seaweed, we ought to be critical.
According to the small amateur experiment (Enclosure 7) Seaweed does burn, but the
process of burning is really slow. Both seaweed and prototype of seaweed mat caught fire
while exposed to the direct flame, although seaweed insulation mat resisted almost three
times longer than loose seagrass. The burned particles carbonized and turned into ash,
not causing any rapid fire spread. The process was comparable the process of burning
wood.
The data available on Neptutherm`s website are mainly agreeing with the experiment`s
result. According to these infromation the material with the salt content of 0,5-2%
achieves DIN 4102 building material class B2, which is defined as normal flammability.
Wood is in the same fire category in this classification system. Unfortunately, the test is
approved only in Germany, and no equivalent test had been carried out in order to define
the fire Euroclass for Posidonia Oceanica. Before results of such test will be available, it is
really hard to elaborate on fire resistance of Posidonia Oceanica according to Danish Law.
(www.neptutherm.com; www.wikipedia.org)
On the other hand, seagrass insulation mats made out of Zostera Marina, another type of
seagrass, are still at the testing stage. According to the interview with Flemming Werk
from Advance Nonwoven, the company tested the seaweed mats unofficially and the
product was highly fire-redundant. (Enclosure 2) This information confirms Bodil Pallesen
from AgroTech, who speculates, that the based on the result obtained from unofficial
tests the company is looking forward fire class B. (Enclosure 3)
7.4. Lifespan and resistance to mold
Seaweed lifespan is doubtlessly its huge advantage compared to other materials. Looking
at the examples form Læsø Island in Denmark, such seaweed traditional roof can resist
form 200 up to even 400 years. That should leave no doubts concerning material´s
resistance to mold, since the roof thatching is not secured in any way against moisture.
However, the only species of seagrass tested concerning resistance to mold is Posidonia
Oceanica produced in Germany. According to manufacturer`s webpage this type of
seagrass insulation achieves mold resistance class 1, which is defined as top quality
materials for medium to high production requirements and basically confirms the
hypothesis of seaweed`s resistance to mold. The tests were carried out by Fraunhofer
Institute in Germany and unfortunately no similar tests had been carried out on either
Zostera Marina or Seaweed Insulation Mats. (www.neptutherm.com; www.teampti.com;
www.naturalhomes.org)
Anna Katarzyna Plawecka October 30, 2015
36
On the other hand, the lifespan of seaweed itself and the
lifespan of seaweed insulation mat is a bit different case.
According to interview with Flemming Werk form Advance
Nonwoven (Enclosure2) Seaweed mats life expectancy
circulates around 20 years, after which the mat can be
produced again form the remaining fibers. However, the ten-
years-old-mat (Figure42) kept outside during all this time
does not look on its age. Even though the mat got visibly
compressed and some vegetation started growing on it, no
signs of either mold or decay are visible. The mat is a
possession of Bodil Pallesen form AgroTech and was
presented on the seaweed workshop. (Enclosure 4)
7.5. All the other virtues of seaweed
Seaweed is considered to be hygroscopic material, which can be a huge advantage
concerning indoor climate. As Jørgen Søndermark from Realdania Byg says, hygroscopic
abilities of seaweed „create surprisingly comfortable rooms, while the ability to absorb
and give off moisture contributes to regulate the indoor climate." (www.dezeen.com)
Adding to it the fact, that seaweed is a vermin-free, no toxic material, in few years we can
expect the product, which can be highly competitive to the standard insulating materials.
(Realdania Byg, 2013)
7.6. Threats
Seaweed`s natural origins create also a certain boundaries. The reason of that is that
nobody can predict what quantity of seaweed can be expected to be harvested.
(www.tangtag.dk) Another limitation is the ecosystem of the sea, in which seaweed plays
important role, and its excessive harvesting could deeply harm the environment.
(www.seagrasswatch.org). Therefore we should be careful and use the resources we have
wisely. “It is still a big challenge” Says Bodil Pallesen from AgroTech, and adds, that we
know now too little about seaweed to determine its future “It will probably be used for
special purposes – and it will not have to be produced in the way Rockwool is- so it is too
early to answer this question” (Enclosure3).
7.7. Part conclusion
All in all, seagrass is a valuable material with a lot of potential. Owning to its various
properties and really sustainable origins the material has a possibility of becoming really
competitive on building market. However, in order to examine deeply its properties and
find out whether the different species of seaweed really have different properties official
Figure 42: Old and new seaweed mat
(Enclosure 4)
Anna Katarzyna Plawecka October 30, 2015
37
tests have to be carried out. On the other hand, the amount of raw materials should be
taken into consideration while thinking about seaweed insulation as a product produced
on a big scale.
8. Conclusion
All in all, seaweed is fascinating material that has many possibilities for becoming
important in the building industry. Its reach history had shown that seaweed insulation
was not used as insulation just out of randomness, because the fact that we have
evidence of usage of seagrass in many different parts of the word and in completely
different times is already a huge proof of seagrass properties. Furthermore, though
history we can examine different methods of gathering, threating and using seaweed and
on this basis can be built modern production and construction methods.
The report proves also, that seaweed is not only material of the past existing exclusively
on the pages of history books. The initiative taken on Danish Island Læsø by Henning
Johansen together with other members of seaweed triumvirate resulted in bringing
seagrass back to life and turning the attention on this new material. I consequence
Realdania Byg came up with the idea of building modern seaweed house which meant
using the old material in modern ways. The project shown that seagrass, even though
natural and not harmonized, can be integrated into beautiful architectural vision, and in
addition fit in the economical frames and tight time schedule. Moreover, the house has
negative carbon dioxide footprint and fulfills the requirements for low energy buildings in
Denmark, which mean consuming no more than 20 KWh per meter squared per year and
equals to Danish energy Frame 2020.
Consequently, the modern seaweed insulation appeared, in form of either loose fill or
insulating mats. In both cases the material is fully natural, sustainable, and really
promising.
Seagrass properties are also exceptional, although in many cases we have to base on
somebody`s opinion rather that official tests. Furthermore, dividing seagrass into species
turned out to be a necessity, since it is not known if their properties are the same, and
comparing the only one known value, which is thermal conductivity, confirms that there
is a difference between them. Unfortunately, it is only hypothesis, the same tests have to
be carried out on both of the species in order to find out whether it is correct or not.
Besides that, seagrass have really good properties and can be competitive on the market
owning to its natural origin and many other virtues. It`s thermal conductivity is
comparable to mineral wool, and its fire class is expected to be class B. Furthermore, it
insulates really well towards sound, is vermin-proof and mold proof, and its hygroscopic
Anna Katarzyna Plawecka October 30, 2015
38
abilities are influencing the indoor climate positively. Moreover, the material is fully
natural and sustainable, which and that matters a lot in nowadays building industry.
However, the fact that seagrass is a natural product of the sea has its pros and cons. In
case of starting the production on bigger scale the problem may be the insufficient
amount of raw material available, therefore the issue of producing seaweed insulation is
actually more complicated than it seems.
All in all, many things we can say about seaweed, but for sure not that it is just a sea
waste lying on the beaches. It is valuable, promising material, with huge possibilities in
the modern, sustainable building industry of the future.
Anna Katarzyna Plawecka October 30, 2015
39
Bibliography
Books
Ehmann, S., Klanten , R., & Borges, S. (2014). Tegnestuen Vandkunsten. In Building Better:
Sustainable Architecture for Family Homes. (pp. 148-153). Berlin: Gestalten.
Jensen, J. K. (2012). Tængemænd og vaskerpiger. København: People`s press.
Jensen, J. K. (2014). Naturens eget tag. København: People`s Press.
Moe, K. (2014). Insulating Modernism. Isolated and Non-isolated Thermodynamics in
Architecture. Basel: Birkhauser.
Nienhuis, P. H. (2008). Environmental History of the Rhine-Meuse Delta: An ecological
story on evolving human-environmental relations coping with climate change and
sea-level rise. In P. H. Nienhuis. Springer Science & Business Media.
Pfundstein, M., Gellert, R., Spitzner, M. H., & Rudolphi, A. (2007). Insulation Materials.
Principles. Materials, Applications. Munich: Brikhäuser.
Realdania Byg. (2013). Den moderne tanghus på Læsø. Odense: OAB-Tryk a/s.
Articles
Cabot, S. (1928). Build Warm Houses with Cabot`s Quilt. Boston: Samuel Cabot Inc.
Wylle-Echeverria, S., & Cox, P. A. (1999). The Seagrass (Zostera MArina [Zosteraceae])
Industry of Nova Scotia (1907-1960). Economic Botany 53 (4), 419-426.
Yang, J. (2012). Properties analysis of seaweed as a traditional building material. Trends in
Building Materials Research (pp. 154-157). Hangzou: Trans Tech Publications,
Switzerland.
Zhang, N. (2011). Idea on low-tech ecological evolution of seaweed house in Jiaodong
Peninsula. Advanced Materials Research Vol. 243-249, 6961-6964.
Webpages
www.iucnredlist.org. Retrieved October 07, 2015, from
http://www.iucnredlist.org/details/153538/0
www.iucnredlist.org. Retrieved October 07, 2015, from
http://www.iucnredlist.org/details/153534/0
www.seagrasswatch.org. (n.d.). Retrieved August 25, 2015, from
http://www.seagrasswatch.org/seagrass.html
Anna Katarzyna Plawecka October 30, 2015
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www.mesa.edu.au Retrieved October 20, 2015, from
http://www.mesa.edu.au/seagrass/seagrass04.asp
www.seagrassli.org. (n.d.). Retrieved August 19, 2015, from www.seagrassli.org:
http://www.seagrassli.org/conservation/history.html
www.usa.chinadaily.com. Retrieved September 20, 2015, from
http://usa.chinadaily.com.cn/epaper/attachement/jpg/site1/20130117/f04da2db
112212618ceb21.jpg
www.duskyswondersite.com. Retrieved September 20, 2015, from
http://www.duskyswondersite.com/wp-content/uploads/2014/09/Seaweed-
houses-Shandong-province-China.jpg
www.china.org. Retrieved September 14, 2015, from www.china.org:
http://www.china.org.cn/china/shandong/2012-06/15/content_25684613.htm
www.chinadaily.com. Retrieved from www.chinadaily.com.cn/opinion//2015-
05/26/content 21192830.htm
www.tangtag.dk. Retrieved October 13, 2015, from www.tangtag.dk
www.dezeen.com. Retrieved 08 25, 215, from www.dezeen.com:
http://www.dezeen.com/2013/07/10/the-modern-seaweed-house-by-
vandkunsten-and-realdania/
www.bygningsreglementet.dk.. Retrieved October 16, 2015, from
http://bygningsreglementet.dk/br10_05_id5182/0/42
www.neptutherm.com. Retrieved August 24, 2015, from www.neptutherm.com:
http://www.neptutherm.com/index.php?home
www.cordis.europa.eu. Retrieved October 07, 2015, from
http://cordis.europa.eu/news/rcn/35568_en.html
www.fraunhofer.de. Retrieved September 4, 2015, from
https://www.fraunhofer.de/en/press/research-news/2013/march/seaweed-
under-the-roof.html
www.wikipedia.org. Retrieved 10 October, 2015, from
https://en.wikipedia.org/wiki/Flammability
www.tempati.com Retrieved 10 October, 2015, from
http://www.teampti.com/Content/Pdf/SPI_Guidelines.pdf
www.naturalhomes.org. (n.d.). Retrieved October 14, 2015, from
http://naturalhomes.org/seaweed-house.htm?a=workshops
Anna Katarzyna Plawecka October 30, 2015
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www.agrotech.dk. Retrieved October 24, 2015, from
http://agrotech.dk/arrangementer/arrangement/workshop-med-toerv-af-tang-til-
straatagets-rygning
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http://agrotech.dk/projekter/project/tang-toerv-til-straatage-nyudviklet-
langtidsholdbar-tangmoenning-0
Anna Katarzyna Plawecka October 30, 2015
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Enclosures
Enclosure 1
Cabot`s Quilt Insulation leaflet – construction solutions (Cabot, 1928)
Anna Katarzyna Plawecka October 30, 2015
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Enclosure 2
Flemming Werk, 2015, Interview with Flemming Werk from Advance Nonwoven A/S,
Interviewed by Anna Katarzyna Plawecka [written] Advance Nonwoven A/S, Moellerupvej
26, 8410 Roende, Denmark, 19th
October 2015
Interview with Flemming Werk form Advance Nonwoven A/S
My name is Anna Plawecka, I am a student of Construction Architecture and I am writing
my dissertation about seaweed insulation. I have prepared some questions regarding
seaweed insulation mats the company is producing.
• How the company came up with the idea of producing mats out of seaweed?
- The demand came actually from a thatcher form Læsø and Bodil Pallesen
form AgroTech. They contacted us and asked if we could produce
insulation mats made out of seaweed, so we gave it a try.
• How long does company produce Seagrass Insulating Mats?
- Around 1 year and only the fire test approval of the product from a
notified body is yet to be settled. The approval is expected in max. 2
months.
• Where do you buy the seaweed from?
- From Bogø Island in Denmark.
• Did you have any difficulties finding out seaweed properties? What researches did
you base on?
- We are still testing the material, but until now it seems to have really good
properties, especially regarding sound and fire. We have tested the
seaweed mats according to fire in our company and it did not burn, but
now we are waiting for official tests to confirm it.
• What about sustainability and carbon dioxide footprint? How much CO2 it is
emitted to atmosphere while producing seaweed insulating mats?
- I have no data regarding production process of the machines itself.
However, the machines do not pollute the atmosphere due to the Co2
filters we have installed.
• How long is the lifespan of seaweed mats?
Anna Katarzyna Plawecka October 30, 2015
4
- The same as any other product this type which means from 20 years and up.
• Want happen when the life span ends? Can they be reused/ recycled?
- They can go through the production process again and the process can be
repeated many times until there will be no fibers to reuse and only dust
will remain.
• Can you explain me production process step by step?
- The raw material first goes through hammer mill, and goes through a
fiberizer and into storage boxes (hopper feeder and weighing system) and
then the binder is added to the material mixed in “mixer”. After that the
material is going through the patented CAFT technology machine which
creates desired density and thickness of the mat. Then the mat goes to the
oven where the heat is used to bond the fibers. In the end mat is cooled
down, cut into required sizes, winded or stacked and packed, wrapped.
• Do you use any additional additives to improve seaweed mats quality?
- No, we only use binder in order to keep fibers together.
• How much time it takes to produce one mat?
- It does not take long, the single process of producing the mat takes around
25 minutes.
• How expensive the production of the seaweed mat is?
- The expenses depend on the market and price of the raw material. In case
of waste material we can be really competitive to the market price. The
production of seaweed did not start fully yet and I am not able to define
how much it will cost.
• Can you use the same machines and techniques as for other materials?
- Yes, we can use the same machines for wide range for product; the only
issue is cleaning the machines while changing from one material to
another.
Anna Katarzyna Plawecka October 30, 2015
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• How big the demand for Seaweed insulation is Mats? Ex. in comparison with other
materials you produce.
- I cannot answer this question, since the material is still at the testing stage
not known in the market. Our estimate is that the market size could be app
30 mill. dkr. per year.
• How many competitors on the market do you have?
- There is no other company on the world using the same technique we are
using.
• Thank you for your time and help. Do you agree that I will use this interview in my
dissertation?
Yes please do,
Signed by
Flemming Werk
Advance Nonwoven A/S
Photographs form the production process of seaweed insulating mats obtained from
Advance Nonwoven:
Anna Katarzyna Plawecka October 30, 2015
6
Enclosure 3
Bodil E. Pallesen, 2015, Interview with Bodil E Palleasen from AgroTech A/S, Interviewed
by Anna Katarzyna Plawecka [written], Kirkevænget 1, Feldballe, 8410 Roende, Denmark,
23rd
October 2015
Interview with Bodil E. Pallesen from AgroTech A/S
My name is Anna Plawecka and I am student of Construction Architecture. I am
writing my dissertation about seaweed insulation and I would like to ask you some
questions.
• How good, in your opinion, is seagrass as insulation material?
o In the top
• What about its lifespan?
o The construction- there is no borders. It is still possible to find really old
houses , where seaweed/eelgrass was used as insulation material
• Seagrass mats produced by Advance-Nonwoven A/S are quite new material. Do
we already know lambda value, acoustic properties or fire classification of
seagrass?
o Lambda value comply with mineral wool one, but remember that it is just a
prototype, and we are actually not ready with all the tests. We are
expecting fire class B according to the temporary tests that we had carried
out.
• How easy in your opinion is work with seaweed on the building site?
o With the right equipment there is no problems
• Do you think that seagrass is expensive material in comparison to other, standard
materials?
o It will probably be used for special purposes – and it will not have to be
produced in the way Rockwool is- so it is too early to answer this question.
• What do you think about the future of seagrass in building industry? Do you think
that it can become as popular as mineral wool or polystyrene?
Anna Katarzyna Plawecka October 30, 2015
7
o Look at the answer above. It needs to be researched if the whole company
should be established, which will just produce pure eelgrass
• In your opinion can it be problematic that demand for seagrass will be too high
comparing to the number of raw material?
o Yes and it requires that salvage of raw material will also be more rational
than now. So it is still a big challenge.
• Thank you for your time and help. Can I use this interview in my dissertation?
o Yes, but remember to write a source, and that the project got the support
from MUDP, environmental protection agency, and partners of the project are
Advance Nonwoven and Henning Johansen form Læsø, and that I am product
developer and project leader from Agro Tech.
Anna Katarzyna Plawecka October 30, 2015
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Enclosure 4
Workshop: ”peat” of seaweed used as ridge finish on straw thatched roof,2015, attended
and reported by Anna Katarzyna Plawecka, Kirkevænget 1, Feldballe, 8410 Roende,
Denmark, 23rd
October 2015
Workshop: “peat” of seaweed used as ridge finish on straw thatched roof.
Basic data of the event:
Date: 23rd
of October 2015
Place: Kirkevænget 1, Feldballe, 8410 Roende, Denmark
Character of the event: open to everybody interested
Project behind the workshop:
The workshop was a part of development project, which had started 1st
of January 2015
and will finish 30th
September 2016.
The project is carried out by the cooperation of Henning Johansen, Læsø´s Seaweed Bank,
Advance Nonwoven and AgroTech, and supported by MUDP (Danish Environmental
Technology and Demonstration Department under the Environmental Protection Agency.)
The aim of the project: Development of “peat-like” structure made out of eelgrass, which
can replace the existing solutions for ridge finish of straw thatched roof and make the
work of thatchers easier.
Description of the event:
The aim of the event was to experiment with the prototype of the new material for ridge
finish for straw thatched roof. The prototype was a mat produced out of eelgrass by
Advance Nonwoven. Event started with quick presentation of the product. The 10-years
old seaweed mat was presented as a proof of long lifespan of the product. During the
event all participants had a possibility to try to work with the material on actual straw
roof and were able develop the best construction solution. The event was run by seaweed
roof thatcher from Læsø Henning Johansen and Bodil Pallesen, product developer and
project leader form AgroTech. (www.agrotech.dk)
Anna Katarzyna Plawecka October 30, 2015
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Enclosure 5
Seagrass: Zostera Marina Specification. (Pfundstein, Gellert, Spitzner, & Rudolphi, 2007)
Density 75 kg/m3
Thermal conductivity 0,043 – 0.050 W/mK
Reaction to fire good, tests in progress
Acoustic properties good, not officially tested
Mold resistance good, not officially tested
Seagrass: Zostera Marina
Specyfication:
Properties:
Name: Zostera Marina
Eelgrass
Habitat (chosen): Denmark
China
United States
Netherlands
Products:
• Seaweed insulating mats produced by Advanced Nonwoven A/S (testing stage)
• Components to The Modern Seaweed House on Læsø
Anna Katarzyna Plawecka October 30, 2015
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Enclosure 6
Seagrass: Posidonia Oceanica Specification.
Density 65-75 kg/m3
Thermal conductivity < 0,039 W/mK
Reaction to fire (according to DIN 4102) B2 (normal flammability)
Acoustic properties good, not officially tested
Heat storage capacity (c) 2,502 J/kgK
Mold resistance class 1
Water holding capacity 1,6 – 3,4 kg/kg
Salinity (about) 0,5 – 2%
Seagrass: Posidonia Oceanica
Specyfication:
Properties:
Name: Posidonia Oceanica
Neptune Balls
Neptune Grass
Mediterranean tapeweed
Habitat: Mediterranean Sea
(Endemic)
• Insulation material produced by NeptuTherm® in Germany
Products:
Anna Katarzyna Plawecka October 30, 2015
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Enclosure 7
Amateur experiment: Exposing loose seaweed and seaweed insulation mats on fire. 2015.
Carried out by Anna Plawecka. 25th
October 2015, Horsens, Denmark.
Samples:
Loose eelgrass sample
Seaweed insulation mat 10 cm x 10 cm, density 80 kg/m3
Procedure:
Both samples were exposed to the direct fire contact one by one, and it was measured
after what time the sample caught fire.
Process:
Sample 1 – loose eelgrass
Fire caught on the eelgrass after around 2-3 seconds
Burning process was clam and did not provoke rapid fire
spread. Burned pieces carbonized and turned into ash.
Sample 2 – seaweed insulation mat 10 cm x 10 cm, density 80
kg/m3
Fire caught on the mat after around 7-9 seconds
Burning process was clam and did not provoke rapid fire
spread. Burned pieces carbonized and turned into ash.
The process of burning was slower in comparison with loose
seaweed.
Conclusions:
Even though both samples caught fire quite fast, it took almost three times longer to for
seaweed mat to start burning compared to loose eelgrass. Additionally, the process was
rather slow and no rapid fire spread was observed, and again, the seaweed insulation mat
was burning slower than loose eelgrass. The burned pieces carbonized and turned into
ash.
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