dissertation seaweed insulation

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

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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!


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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.


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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


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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.


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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


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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


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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


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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


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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?


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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.


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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)


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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


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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)


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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)


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)


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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)


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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)


17

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)


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)


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)



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



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)


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)


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,



23

on the contrary the process is at least twice as fast as the traditional one. (Jensen,


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,


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


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)


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


Figure 27: External cladding made out of

seaweed stuffed into kitting net (Realdania

Byg, 2013)


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)


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)


28

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


Figure 30: Prefabricated wooden

element filled with dried seaweed


Figure 31: Filling the nets with dried

seaweed. (Realdania Byg, 2013)


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.


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)


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



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.


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)


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)


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.


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.


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)


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.


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).


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)


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


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.


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


40

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


41

www.agrotech.dk. Retrieved October 24, 2015, from

http://agrotech.dk/arrangementer/arrangement/workshop-med-toerv-af-tang-til-

straatagets-rygning

www.agrotech.dk. Retrieved October 24, 2015, from

http://agrotech.dk/projekter/project/tang-toerv-til-straatage-nyudviklet-

langtidsholdbar-tangmoenning-0


1

Enclosures

Enclosure 1

Cabot`s Quilt Insulation leaflet – construction solutions (Cabot, 1928)


2


3

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?


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.


5

• 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:


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?


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.


8

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)


9

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


10

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:


11

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.

dissertation seaweed insulation

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