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Cool room insulation

Keeping the “coolness”

Kenneth Lekashman – Soraya Manzor

6/10/2014

To design and analyze different insulation materials that use locally available resources in Kenya and preferably Agricultural Waste.

Cool Room Insulation Design

ContentsIntroduction......................................................................................................................................2

Background.......................................................................................................................................3

Effects of Temperature on Fresh Horticultural Products................................................................3

Insulation Materials and their Limitations.....................................................................................4

Agricultural Waste: Rice Hulls........................................................................................................4

Thermal Conductivity and our Target Value:..................................................................................5

Design Process..................................................................................................................................6

Design considerations and criteria.................................................................................................6

Concept evaluation/Idea selection.................................................................................................7

Methodology of Construction........................................................................................................8

Methodology of Testing..................................................................................................................11

R-value Background.....................................................................................................................11

D-lab Field Test Procedure...........................................................................................................12

Results.............................................................................................................................................14

Conclusions.....................................................................................................................................16

Future recommendations..............................................................................................................17

Appendix 1: R-value testing records and calculations.................................................................18

Appendix 2: Pictures taken during the construction....................................................................19

Bibliography...................................................................................................................................20

1


Introduction

The agricultural sector in Kenya provides income for over 75% of the population and

generates nearly 30% of the nation’s GDP (Gubbins, D-Lab 1 Report), but it is estimated that

greater than 30% of produce is lost to spoilage before it reaches consumers. The loss is driven by

many factors whose relative contributions are difficult to quantify, but include: appropriate

handling and post-harvest practices, counter-productive policies - such as applying levies per

package, rather than by weight, which encourages use of large bags, overfilling, and finally a lack

of cold storage access across the supply chain (Gubbins, D-Lab 1 Report). As a result farmers must

sell their produce immediately after harvest, weakening their ability to negotiate prices and

resulting in inconsistent and suboptimal income (Gubbins, D-Lab 1 Report). Issues of postharvest

loss extend beyond the farmgate and exist at every step throughout the cool chain. Within this

dilemma exists opportunity in the horticultural sector in Kenya. Addressing the causes of

postharvest loss will enhance profits for farmers, increase consumer access to nutritious foods,

and reduce the environmental impact of the agricultural sector meaning that adding a reliable

form of cold-storage could be a potential game-changer.

Researchers at the University of Nairobi, in collaboration with the Horticulture

Collaborative Research Support Program (Hort CRSP) at UC Davis have begun a feasibility study on

using a low cost cooling system known as the CoolBot to reduce postharvest loss at its most

vulnerable stage, immediately after harvest. The proposed innovation seeks to address the

challenges at the farmgate of the horticultural commodities value chain. However, the CoolBot

technology is only part of the equation, the other issues being energy management, farming

practices, and finally the insulation and structure of the building to hold the horticultural products.

Our group looked at and analyzed various potential insulation solutions using agricultural waste.

Based upon a D-Lab 1 report, talking with our mentor Jim Thompson, and time-constraints we

honed in on one specific method of a mixture of Portland Cement with rice hulls. While other

possible insulative methods were considered and will be discussed in this report, all of our testing

and prototyping was limited to this method.

2


Background

Effects of Temperature on Fresh Horticultural Products

In Kenya, the storage of fresh horticultural products at ambient temperatures is limited

from a few days to a week. This means that instead of dealing with pests and disease which are

huge problems in countries like the United States, the issue becomes more centered around the

freshness and mitigating damage to the product in transit. Horticultural products left in the sun

can reach 13-16°C above ambient temperatures. Ambient temperatures are well over 30° C in

much of Kenya. This has the effect of increasing deterioration over 20 times of that of 0 °C

(Gubbins, D-Lab 1 Report) For every ten degrees, a product’s post-harvest life is halved. Low

temperatures reduce metabolic processes that incur spoilage from disease and ethylene, this

makes the prospect of cheap cooling technology very attractive.For optimized cost-effectiveness,

cool rooms should be built in places where the most damage occurs and the most produce is

passing through on its way to markets. If placed at these vital junctions, losses to heat and sun

damage will be minimized, allowing farmers to yield higher profits from their produce.

Case Study: Ghana

An example of this in practice already exists. In Ghana, the CoolBot cold room was

compared to a traditional storage shed used for several months of storage for onions. Losses were

reduced from 30 to 5% and market value increased from $ 0.50/kg for onions sold immediately

after harvest to $ 2.00/kg for onions sold four months later during the off season (Roy). The costs

for constructing an insulated 20-m2 room of 6 MT capacity, equipped with a window style air

conditioner (10,000 BTU) and a CoolBot controller ($ 300) totaled $ 4300. Recurring costs were $

580 for electricity costs for initial cooling ($ 80/MT at $ 0.09/kWh) and cold storage at 1°C for 4

months ($ 25/month at $ 0.09/kWh). A return on Investment occurred within a single season and

the attempt was immediately profitable (Roy). The high value of stored onions sold during the off

season provided a gross return of $ 10,820 compared to $2100 for onions sold immediately after

harvest, for an additional profit of $ 8720 per 6 MT load (Roy). Even if a back-up 3.5 kW generator

is required, the cost ($ 4900 plus fuel) could be covered by only 2 or 3 uses of the CoolBot

equipped cold room (Roy).

3


Insulation Materials and their Limitations

Current Insulation Materials and Environmental Concerns

In order to use these Cool-bot systems efficiently and economically, the actual physical

structure needs building envelopes that can minimize the ingress of heat and moisture from the

exterior environment. For this reason, thermal insulation of the external walls and roof is essential

for a building using a Cool-bot modified air conditioning unit. Common choices of thermal

insulation are fibreglass, rock wool and mineral wool (Infante). Research has indicated that there

are environmental hazards associated with these materials. The small particles from fibreglass and

glass wool insulation can cause health hazard and respiratory or skin irritant (Infante). Breathing

fibres may irritate the airways resulting in coughing and throat irritation. The Seventh Annual

Report on Carcinogens lists glass fibres of respirable size as a substance "reasonably anticipated to

cause cancer in humans” and concludes that and concludes that on a fiber-per-fiber basis, glass

fibers may be as potent or even more potent than asbestos (Infante). Considering the fact that the

current popular insulation materials have negative side effects from the production stage until the

end of their useful lifetime it becomes is necessary to search for alternative insulation materials

which can satisfy the new standards for environmental and health impacts.

Agricultural Waste: Rice Hulls

One possible alternative exists in agricultural waste. Throughout the world, more than 100

million tonnes of rice hulls are generated each year (Panyakaew). Rice is also processed on a daily

basis meaning that there is year round access to it. The thermal conductivity of rice hull has been

measured using equipment built and operated in accordance with ASTM methods and this

suggests that thermal conductivities of rice hulls are between 0.046 – 0.057 W/mK (Panyakaew).

These values compare well with the thermal conductivity of excellent typical insulating materials

which are either more expensive or have associated environmental concerns. For these reasons,

rice hulls became our primary source of agricultural waste in our brainstorming design and later

prototypes.

4


Thermal Conductivity and our Target Value:

When considering any material as a new insulator one of the biggest properties is the

thermal conductivity of the substance. Thermal conductivity is simply a measure of the amount of

heat transfer that a material can conduct at different temperatures. When it comes to insulation

materials one is looking for a low thermal conductivity. The lower the conductivity the better the

material is able to act as a barrier to temperature changes outside of the insulated structure

(Gubbins, D-Lab 1 Report). The other property that is analyzed is density. Generally most buildings

only have a finite amount of space for which to fit insulation material. The culmination of these

two properties are combined into the R-value. The R-value then becomes a basis for which the

thermal resistance of different materials are compared (Gubbins, D-Lab 1 Report). In general, the

higher the R-value, the better the material tends to act as an insulator. As mentioned above, rice

hulls performed an R-value test between .046 -.057 W/mK. Expanded polystyrene (EPS) which is

the white foam you see in disposable coffee cups and beer coolers. has a nominal R-value of 4 per

inch (Bailies). This became the target-value for our testing and design.

5


Design Process

Design considerations and criteria

Since the problem was identified as mentioned above, we listed the main considerations

and put them into a decision matrix (Table 1) to evaluate our possible designs and decided which

one would be the best according to the most relevant for our purpose.

Design Considerations:

1. Insulation material has to have a high R-value, better than EPS foam.2. In order to increase the R-value, the insulation material has to be able to trap air in as part

of its structure.3. Insulation material has to be water resistant.4. Insulation material has to be able to avoid air moisture condensation.5. Insulation material has to be non-flammable.6. Insulation material has to be wind resistance.7. Insulation material has to be locally available.8. Insulation material, if not commercially available, has to be made out of local resources.9. Insulation material, if not commercially available, has to be made by local inhabitants

according to their technical skills training.10. Insulation material has to be low cost as possible.11. Insulation material has to be malleable as possible to adjust to the different building

options.

Table 1: Decision matrix according to the most relevant design considerations

PRODUCT Cost W Skills W R-Value W Climate resistant

W Ag. Waste

W Total

Composite rice hull boards

4 3 4 2 0 4 3 3 4 2 37

Concrete slabs with loose fill rice hulls

3 3 3 2 0 4 4 3 3 2 33

Wooven mesh and loose fill rice hulls

3 3 5 2 0 4 3 3 4 2 36

Adobe 5 3 4 2 0 4 2 3 3 2 35Tetrapack 3 3 3 2 0 4 4 3 2 2 31

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Criteria:

The criteria to test the insulation material prototypes were decided to be the R-value of

the material, moisture content, flammability and cost. The metrics and target values for these

criteria are detailed in Table 2.

Table 2: Criteria, metrics and target values for design

Criteria Metric Target valueR-value greater than EPS foam ft2*ºF*h/BTU*in 3.85-4.0 (EPS foam)Moisture content mg of water Less than construction valueFlammability Development of a flame NonCost US$/m2 3.125

Concept evaluation/Idea selection

At the time we evaluated our possible product designs, the decision yielded by the

decision matrix was to design composite rice hulls boards. This decision was made without

knowing exactly the R-value of the product to be constructed. The options we brainstormed for

the construction of composite rice hulls boards were:

a) Rice hulls and resin

b) Rice hulls and cement

c) Rice hulls and latex paint

After several conversation with both mentors (Kurt Kornbluth and Jim Thompson), we

decided to build the boards out of rice hulls and cement, now called hybrid material. Part of this

decision was based on the small scale prototype that Jim Thompson gave us and his desire of find

out how this material would work in different proportions and under compressibility addition.

The next step in our decision was to put or not another material in order to provide a

support structure to the rice hulls board. These options, later constructed, were:

a) SIP1 style: The panels consist of a hybrid material core sandwiched between two structural

facings, typically oriented strand board (OSB).

1 SIP: Structural Insulated Panels. http://www.sips.org/

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b) Concrete support: Board made out of three similar thickness layers. The first layer consists

of a concrete layer followed by a layer of hybrid material and finally covered by another

layer of concrete.

c) Mesh/concrete support: Board made out of three layers. The first layer consists of a thin

layer of concrete with a sheet of mesh immersed in it, followed by a thicker layer of hybrid

material and finally covered by another thin layer of concrete with a sheet of mesh

immersed in it.

d) Just hybrid material

Methodology of Construction

The construction process took place at the Student Farm at UC Davis Campus during the

month of May 2014.

1. The first stage of construction was the construction of the molds. After a brainstorming

with Professor Kurt Kornbluth, we decided to build molds made out of 2x4 slabs of wood

in a 12x12 square inches of light shape. See schematics in Figure 1.

Materials: 2x4 in slabs of wood, 4 in self-drilling screws for wood, driller and screwdriver bits.

8

Figure 1: Molds construction schematic


2. The first prototypes were mainly constructed to learn how to treat the materials and how

to add strength to the boards according to the concept evaluation mentioned above.

The general construction step by step procedure is detailed in Table 3.

Table 3: Board construction general procedure

Process Stage Materials & Quantities Explanation

Rice hulls preparation Bucket1 part of rice hulls + 1 part of water

Let it soak in a bucket for half an hour

Cement preparation BucketDriller with a paint mixer attachment1 part of cement + 0.5 part of water

Mix it until it gets homogeneous.

Mixing Bucket with the prepared cementDriller with a paint mixer attachment

Pour the prepared rice hulls into the prepared cement one handful by handful

Pouring into molds Wooden moldsDry cement (less than a handful)

Sparse a little of dry cement on the surface at the bottom of the mold. Then pour the mix into the mold at the thickness desired.

Setting for drying Flat board Set all the molds (before pouring) in a flat surface that can be move to a place to let it dry.

Unmolding Drill with screwdriver bit or just a simple screwdriver

Take off 4 of the screws that are attaching one of the sides of the mold. Then remove the slab piece carfully. At last, remove the rest of the mold by lifting it.

The exact measurements that were used in the prototype construction were:

Per 1/4 batch

-8L of rice hulls + 8L of water

-2L of cement + 1L of water

Per 1/3 batch

-9L of rice hulls + 9L of water

9


-3L of cement + 1.5L of water

10


Methodology of Testing

R-value Background

The R-value Rule requires that all types of insulation (except aluminum foil) be tested in

accordance with one of four standard test methods defined by ASTM, the American Society of

Testing and Materials. The rule requires that R-value tests be conducted at a mean temperature of

75°F (23.9°C) and a temperature differential of 50°F (27.8°C). This means that insulation is usually

tested with the cold side at 50°F (10°C) and the warm side at 100°F (37.8°C) (Bailies).

The four R-value tests are:

1. ASTM C 177, Standard Test Method for Steady-State Heat Flux Measurements and

Thermal Transmission Properties by Means of the Guarded-Hot-Plate Apparatus.

“This test measures the steady-state heat flux through homogeneous flat specimens. Two test

specimens (as identical as possible) are placed on both sides of a ‘guarded’ hot plate and in

contact on the other side with a ‘cold surface assembly.’ This test requires the establishment of

steady-state conditions and the measurement of heat flow in one direction. It is used to measure

the thermal resistance of thin-sliced test specimens at short time intervals (up to six months).

However, its measurements can be used to estimate the predicted aged R-value for longer

periods, typically 2.5 to 40 years” (Knowles).

2. ASTM C 518, Standard Test Method for Steady-State Heat Flux Measurements and

Thermal Transmission Properties by Means of the Heat Flow Meter Apparatus.

“This test measures steady-state thermal transmission through flat slab specimens using a heat

flow meter. One test specimen is placed between a cold plate and a hot plate. (One or more heat

flux transducers can be employed.) As with ASTM C 177, it is used to measure the thermal

resistance of thin-sliced test specimens at short time intervals, but its findings can be used as the

foundation for aged values” (Knowles).

11


3. ASTM C 976, Standard Test Method for Thermal Performance of Building Assemblies by

Means of a Calibrated Hot Box.

“The calibrated hotbox method is especially suited for large non-homogeneous specimens such as

building structures and composite assemblies. It can also be used for measurements of individual

building elements such as windows and doors. The chamber can be configured for attics and floors

or wall assemblies” (Knowles).

4. ASTM C 1303, Standard Test Method for Estimating the Long-Term Change in the

Thermal Resistance of Un-faced Rigid Closed-Cell Plastic Foams by Slicing and Scaling

Under Controlled Laboratory Conditions. (This test actually is an estimate employing

short-term measurements to predict R-values of foam plastics over a longer period, and

not an actual measurement).

“This test allows for estimates of long-term change in thermal resistance of un-faced foam plastic

by reducing the sample thickness to accelerate aging under controlled laboratory conditions. Some

products, such as polyisocyanurate (polyiso) board with facers and spray polyurethane foam (SPF),

may be inappropriate for this method due to their non-homogenic nature, and their adherence to

facers or substrates” (Knowles).

R-values reported from tests can vary depending on how the samples were prepared, their

thickness, and the type of apparatus used. With the various testing methods available, there is

bound to be confusion over why there is no singular way universally accepted for measuring

insulation R-values. Unfortunately, there is no one test that works best for all products. Instead,

we are left with the process of determining the most appropriate methods, sample preparations,

and conditioning procedures that are accurate, reproducible, and relevant to specific material’s

actual field performance (Knowles).

D-lab Field Test Procedure

Knowing that adhering to the American Society of Testing and Materials (ASTM) standards

requires very specific conditions that we could not replicate in the D-Lab workshop; we came up

with our own test to see how our cement-rice hull mixture insulation panels compared with EPS

12


foam. The summary of the test is as follows, essentially we wanted to take a block of ice, put it in a

bucket which had a hole in the bottom, with the insulation panel over the top working as a lid, and

then measure the amount of water that melted from the ice block at certain time intervals. We

would measure until the ice melt intervals had become constant, which in our testing occurred

after approximately 1 hour. The test was later modified to using ice cubes instead of an ice block

which would be created simply by filling up our buckets with water then and letting them freeze,

as we did not have access to a large enough freezer to be able to hold 10 different buckets. The

buckets themselves were actually cylindrical styrofoam coolers meant to be used for drinks and

refreshments. We cut them to 4 inches in height, so as to reduce the amount of air that would be

present in the test and impact our results. We then took a blowtorch and heated up a screwdriver

to make a hole in the bottom of the bucket for water to leak out. Our test was conducted indoors

rather than outdoors because the sun’s radiation would add an additional variable into the

equation, and our test had enough variables as is and we wanted to limit one we could. We then

filled the buckets to the brim with ice cubes, and set them tilted with a measuring cup below

them. Eight of the buckets were insulation panels that were 4:1 rice to concrete, 3:1 rice to

concrete, compressed vs uncompressed and a series of replicates for each of these. We labeled

the insulation panels accordingly. The other two buckets were one being covered with .5” of EPS

foam (which has a known R-value of 3.85-4.2 per inch) which was our target and open air. These

two were meant as controls. The test began by setting measuring cups below and allowing melted

ice water to start draining into the cups. Since there were only two of us, we were forced to

measure the ice melt at time intervals that were individual, because we could not measure them

all at the same time until the very end. Perhaps the largest flaw with the test is that approximately

60% of the area of the testing apparatus was the same EPS foam for all 10 buckets. Our insulation

panels, and controls only represented approximately 40% of the area of the testing apparatus, and

this without a doubt impacted our results. Additionally, evaporation obviously impacted the

amount of water at the end of the test. Other flaws might include there not being a consistent

mass and amount of ice, because although the buckets were all filled, the ice cubes themselves

were of various shapes and sizes and could potentially have more or less room for air which could

impact the results. Our test was very much a cursory estimate to see if the prototypes were even

viable.

13


Results

The measurements taken along the test are detailed in Appendix 1 for future discussion of testing validation. The final measurements are plotted in Table 4 as it follows.

3,O C1 4R 3,C,O 4,O 4,C,R 3,R C2 (Open)

3,C,R 4,C,O0

20

40

60

80

100

120

140

160

Final melted water volume

Wat

er v

olum

e, m

L

Figure 2:Test results (rough)

The final measurements allowed us to see the main differences among the prototypes and more important, compare all of them with the EPS foam control as well as the “open” control.

To calculate the R-value, equation 1 was used in order to determine a value comparable with that found in the literature for EPS foam (Target value)

Equation 1

The results for each prototype are listed and plotted in Table 4 and Figure 3 respectively.

14


Table 4: R-value values

3,O C1 4R 3,C,O 4,O 4,C,R 3,R C2 (Open)

3,C,R 4,C,O0.000

0.200

0.400

0.600

0.800

1.000

1.200

1.400

1.600

1.800

2.000

1.473

1.794 1.7491.554 1.572 1.537 1.521

1.036

1.646

1.217

R (ft2*°F*h/BTU*in)

Figure 3: Test results (R-value calculation)

15


Conclusions

In conclusion, our limited test proved that it actually worked and yielded some interesting

results. Despite the fact that approximately 60% of the structure was the same for each test-

sample, we saw a significant difference in the amount of water melted in our sample with no

insulation lid in comparison to either our control of EPS foam or our eight rice-concrete samples.

EPS Foam has been experimentally tested under the ASTM standards of R-value and is supposed to

perform in the range of 3.85-4.2 per inch. After calculating backward from the amount of water

melted, we found that our .5” of EPS foam performed at approximately 1.8 ft^2 *˚F*h/BTU*in.

This is roughly where we expected it to be based off our sample. Our best performing sample

performed almost as well at 1.7495 ft^2 *˚F*h/BTU*in which was just under the EPS foam sample.

In terms of the other variables that we were testing, we saw no real performance increases from

either the change of the 3:1 ratio of rice to concrete as opposed to 4:1, and compressed vs

uncompressed. This result yields interesting implications for future tests. One of the biggest issues

we had related to the strength of the samples. As we were working with a very limited time frame

and concrete takes approximately 28 days to reach full strength, and we had to test our samples

after only a week, we experienced significant crumbling on the part of many samples most

noticeably 4, C, O (4:1 ratio, Compressed, Original). This crumbling no doubt impacted the results

significantly as that sample performed not as well as the other samples. We expected the

durability of the panels to be impacted by our earlier decision to build thin for testing purposes;

(we knew we could later use math to find the value of it per inch so we wanted all of our test

samples to be the same height) so we were not too surprised to find our test samples weaker than

some of our earlier, and thicker panels (3”).

16


Future recommendations

While the testing revealed that the rice-hull-concrete mixture had comparable thermal

conductivity to EPS foam the work is by no means complete. The first order of business would to

be to create a completely standardized procedure for the mixing process. While in our tests we

recorded how much Portland Cement, Rice, and initial water was added to our mixture there were

many flaws in our procedure. As part of our mixing process the rice was wet with water and was

not left in a for a set period of time or drained for a set period of time. Creating a set period of

time spent in the water, and spent draining would help keep the amount of water more consistent

as this definitely yielded great differences in each prototype. In the actual mixing, our sole tool

was a drill attachment that you would use to mix paint. This was by no means the best tool and left

clumps of concrete around the sides of the bucket which we attempted to fix. The addition of a

better mixing implement even like a cement mixer could potentially create a much better mixture

with less clumps of cement and yield some better results. In addition, while compression vs

uncompressed yielded no real insulation improvement that we could discern, we recommend that

all future samples be compressed. The compressed samples, simply were easier to transport, and

overall had greater physical strength than there uncompressed counterparts. We would also

recommend that even longer than a week be waited to allow the concrete to fully dry, as our

samples became much more durable with time, and the initial handling after only a week made

some structural damages that led to them being very crumbly and not reaching their full strength

potential as the concrete had more time to dry.

In addition our test was performed only one time, and did not give us any real insight into

whether the different ratios played a role in greater or lesser thermal conductivity. Additionally,

testing would be needed to see what is the optimal ratio of cement to rice hulls. Furthermore, our

testing was done with Portland Cement which was acquired at Ace Hardware in Davis. If it is a

possibility, using the cement that is available in Kenya and tailored to their local availability would

be very useful and more applicable for the client. If we were to run the same test again, I would

like to compare the rice-hull-cement mixtures to other known materials like fiberglass, rock wool,

etc, in addition to EPS to see how those insulators compare as well. Even better, would be to take

the samples and send them to a facility which is able to properly test according to the ASTM set R-

17


value standards such as, the NAHB Research Center, Greenguard Environmental Institute, or the

National Institute of Standards and Technology. Once more initial testing has been done and we

are more confident in our prototypes, sending them to a facility like these would yield great insight

into the real R-value of our products and yield much better data than our limited experiment that

we conducted.

Much more work needs to be done in terms of thinking about the actual construction

technique of using this material in addition to figuring out the structure itself. One possibility could

be to potentially fill some sort of poly-propylene bags used in grain storage with the concrete-rice

mixture. Since we saw no difference between uncompressed vs compressed and our panels were

still quite susceptible to breakage the material definitely needs to be contained in some capacity.

Another possibility could be in the creation of more densely packed, and tighter bricks. If the

strength could be increased through smaller surface area, these bricks might make excellent

building materials. Additionally, since this will most likely be a high mass form of construction, the

ceiling will play a vital role in the final product. With high mass, this means if the sun has much

exposure to the walls, the interior of the cool room will really heat up. If we can limit the suns

exposure through actions such as extending the ceiling perhaps a full meter over the cool room,

this would provide more than ample shade and reduce sun radiation and exposure. Another

element that must be considered is the floor itself. The floor has great potential to provide a great

addition of cooling effects or be a heat sink if it is not also analyzed. Extensive work is needed to

be done on the project, these initial tests only really showed that the technology is worth further

exploring.

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Appendix 1: R-value testing records and calculations

Appendix 2: Pictures taken during the construction


Bibliography

Bailies, Allison. "Big News: The R-Value of Insulation Is Not a Constant." Big News: The R-Value of Insulation Is Not a Constant. Vanguard Block, 24 Apr. 2013. Web. 02 June 2014. Gubbins, Mitchell, and Adrianna Amsden. "Cool Room Insulation." D-Lab(2014): Web. 8 June 2014. Infante PF, et al., (1994). Fibrous glass and cancer. American Journal of Industrial Medicine, 26: p. 559-584. Knowles, Mason. "Understanding Insulation R-value."Greenbuildingsolutions.org. IGCC, 2014. Web. 7 June 2014. Roy, S.K. "Appropriate Postharvest Technologies for Small Scale Horticultural Farmers and Marketers in Sub-Saharan Africa and South Asia – Part 2. Field Trial Results and Identification of Research Needs for Selected Crops." Http://ucce.ucdavis.edu/. University of California at Davis, 2012. Web. 7 June 2014. S Panyakaew, S Fotios. “Agricultural Waste as Thermal Insulation for Dwellings in Thailand: Preliminary Results.” PLEA 2008 - 25th Conference on Passive and Low Energy Architecture. Dublin, October 2008.

Additional Links:

Link of different locations to send to be R-value tested: http://www.naima.org/insulation-resources/research-labs-environmental-testing-certification-organizations.html

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