Design for the Environment/Residential Wall Insulation

Insulative materials work to reduce the transfer of heat. In residential applications their purpose is to allow a residential home to maintain a different temperature environment than the external surroundings without excessive energy inputs. Three insulation materials were chosen for a comparison to determine the most suitable material to be used in residential wall insulation. The three alternatives were rock wool, cellulose paper and flax paper. With increased public awareness with regards to environmental issues, future home owners would benefit from knowing which of the three materials provides the least environmental impact, best functional performance and is the most economical choice; and these factors were the basis for the comparison.

Mineral wool is manufactured from an abundant natural resource in volcanic diabase rock. This natural resource produces 38,000 times more rock then is being used to manufacture the mineral wool. This material is then put into a furnace and heated to 1500°C. This liquid stone is then spun into fibres and blown by gas to make them finer until the ideal material properties are achieved. Mineral wool has been installed in houses as an insulation material from as early as the 1880’s .

Flax plant used in insulation.

Flax paper is manufactured from the unused portions of the flax plant. Combinations of coarse and fine flax fibres can be blended and processed to produce the insulative material . The flax plant has been used since the Neolithic times but only recently has emerged as an insulating material because of its biodegradable nature and low health risk (as opposed to the once widely used asbestos insulation).

Cellulose paper is an environmentally friendly choice because it is made of 80% recycled newspaper. Both cellulose and fibres are chemically treated with a non-toxic substance to resist fire, insects and mould . Cellulose paper has been used in residential insulation since the 1980’s .

Project Information

Section 2 (Group 18)

Ahmad Osman (osmanah1)
Justin Baney (Justin B)
Suthakar Sabapathy (sabapath)
Kobtham Chotruangprasert (kobthamc)

Highlights and Recommendations

Functionally, each of the three alternatives provide low heat transfer values and high sound absorption coefficients. In addition to this, rock wool is naturally resistant to fire, has low water absorption and is not very hospitable to living organisms. Whereas flax and cellulose require additives for fire safety, are more susceptible to absorbing water (which would in turn increase their heat transfer values) and can develop mould under moist and humid conditions.

In both the streamlined lifecycle assessment (SLCA) and the economic input-output life cycle assessment (EIOLCA) rock wool had the best performance. In the SLCA rock wool received the highest overall score of 63 (out of 100). Rock wool received consistently high totals (except in the area of gaseous emissions in which all alternatives faired poorly). It distinguished itself apart from the other alternatives in the material selection portion of the analysis with a very high score of 17 (out of 20). The major issue with cellulose was that there were many solid residue emissions at several points during the lifecycle including the requirement that material be land filled at the end of life. The issue with flax had to do with the energy expenditures required and residues produced during the manufacturing stage in which it ended up receiving a score of 5 (out of 20).

The chart below summarizes the findings for 1000 houses from the EIOLCA:

	Rock Wool	Flax	Cellulose
Economic Activity (million of dollars)	$1.69	$3.45	$3.34
Conventional Air Pollutants (MT)	$37.11	$59.08	$25.95
Greenhouse Gas Emissions (MTCO2E)	$1120	$2664	$1420
Toxic Releases (kg)	$1670	$3395	$1980
Energy (TJ)	$15.5	$35.8	$19.3
Use Phase (amount saved in dollars)	$90,942,500	$91,503,000	$92,183,500

These results show that rock wool has the least environmental impact out of all three alternatives followed by cellulose and then flax. Rock wool has lower amounts of toxic releases, green house gas emissions, and energy requirements. Cellulose emits fewer conventional air pollutants than rock wool but has higher emissions in the other categories. Flax generates more economic activity than the other alternatives which is beneficial but this is at the expense of very high emissions in all the other categories. The savings during use phase are substantial for all alternatives, although the differences between each one are not significant.

Residential wall insulations save energy during the use stage of the material and when considering overall costs there are actually savings. The savings are considerably high for an insulation lifetime of 50 years for all three materials.

The chart below outlines direct and indirect costs for 1000 houses:

	Rock Wool	Flax	Cellulose
Direct Costs ($)	-$16,782,417	-$10,152,842	-$16,356,620
Indirect Costs ($)	$3750	$5,969	$2625
Total ($)	-$16,778,667	-$10,146,873	-$16,353,995

The savings are highest for rock wool with cellulose having comparable savings. Cellulose had lower indirect costs due to lower conventional emissions but rock wool makes up for these in lower material and manufacturing costs. Flax has higher costs than both but despite that it is still able to provide an overall cost savings.

Throughout this study rock wool insulation has shown itself to be the best choice in terms of functional properties, reduced environmental impact, and economics. It is the recommended choice to be used future residential wall insulation applications.

Functional Analysis

The primary function of wall insulation is to slow the heat transfer across the wall in order to reduce the cost of heating and cooling the house. Although this is the primary function of wall insulation there are other functional considerations. These considerations include the material’s ability to resist fire; its water absorption properties; its acoustic insulation properties; and its resistance to insects, mould and other pests.

Functionally these insulation choices are very similar as they all provide low values of heat transfer and high sound absorption coefficients that are all within range of each other. Rock wool has a thermal conductivity value of 0.038 W/m°K, flax paper has a value of 0.037 W/m°K and cellulose paper has a value of 0.035 W/m°K . Each of the materials have sound absorption coefficients ranging from 0.9 to 0.95 .

There are a few differences in functional considerations such as how well each material resists fire. It was discovered that rock wool is naturally resistant while flax and cellulose paper require additives for fire prevention. Other differences were found where rock wool is resistant to living organisms while flax and cellulose paper can develop mould under certain conditions.

Despite the fact that flax was the best economic choice when considering heat loss, it was only marginally better than rock wool. Also, flax and cellulose are more susceptible to water absorption than rock wool ; this in turn would increase their values of thermal conductivity, indicating that in practice rock wool may actually be the best choice in this category as well. Collectively, these properties indicate that rock wool appears to have the best overall properties when it comes to functionality.

Streamlined Life Cycle Assessment

A streamlined life cycle assessment (SLCA) has been preformed for each of the three alternatives. Performing a SLCA encompasses all stages of the product life cycles and allows for consideration of environmental stressors that may have otherwise been missed. The SLCA is also a simple assessment that allows for comparison between alternatives. Rankings for each category range from 0 to 4 with 0 being the worst and 4 being the best.

Rock Wool Insulation

Pre-manufacturing

The main raw materials in the pre-manufacturing of rock wool is 71% natural stones such as diabase, Gotland stone, lime stone, and bauxite, which are used in the production of briquettes . Industrial waste also contributes to 21% of raw materials, specifically from cement and steel production, and also from disposed stone wool waste . Materials such as phenol, formaldehyde, and urea are produced on site and contribute to 8% of the total material input; these are used as binders in the manufacturing process . The raw materials used are in abundance, and the pre-manufacturing stage incorporates the waste of other industries (specifically the steel industry) as material inputs .

However, toxic materials such as phenol and formaldehyde are also used as binders and are material inputs . The total energy used to generate briquettes and binders are 0.62MJ and 2.66MJ respectively, which is not very high when compared to other alternatives . This product also minimizes the use of virgin materials. The score for solid residues is high because they are reusable, whereas the liquid and gaseous residues produced are not.

Manufacturing

A large portion of the material that is used to create rock wool comes from the byproducts of the steel making industry . Also, the rock wool itself is recyclable and reusable, therefore, the score for material use is high. The manufacturing process for the creation of stone wool is very energy intensive. The energy consumption to create one kg of stone wool is 15.1 MJ, which is considerably high . A large amount of the residues are either recyclable or can be used in other industries. For example, the waste material in briquette production is used in Grodan production and other production sites .

Packaging and Product Delivery

The stone wool is packaged into polyethylene foil, and then transported via trucks, to the desired destination . Care must also be taken in handling the material, because it has been known to cause irritation . The energy used to transport the material is considered a fraction of the energy used to manufacture the material. For transportation, no liquid and solid residues are used, however air emissions are significant. However, solid residues from the packaging exist.

Product Use

Rockwool stud cavity insulation of drywall assembly under construction, showing completed firestop made of stuffed rockwool and self-leveling silicone firestop caulking on top.

No additives are necessary for enhancing the properties of the rock wool material. Using an Australian standard, the AIS Granulated rock wool was given the best possible results, which was a zero rating for ignitability, spread of flame, heat evolved, and smoke developed categories. In general, rock wool is the only material to give a noncombustible rating when tested to international standards such as ASTM E-136-82, and ISO R1182 . Therefore, no fire retardant chemicals are necessary. This material also has no nutrients and therefore, no mould build-up will occur. There are low amounts of solid, liquid, and gaseous residues. However, there are still small amounts of rock wool emissions for all three residues during this stage. A very small portion of solid waste is hazardous, while nitrogenous matter and phosphates are emitted into waste water. Also, small amounts of ammonia, hydrocarbons (except CH4), and VOCs (Volatile Organic Compounds) are released into the air .

Recycling/Disposal

Rock wool is highly recyclable and can be put back into the pre-manufacturing and manufacturing processes . For the energy consumption, trucks must be used to transport the material and energy must be used to filter the material . Since this material is recyclable, it receives a high score for solid waste, and liquid waste. However, a lower score is given to gaseous residues because of the emissions into the air caused through truck transportation.

Flax Insulation

Pre-manufacturing

The primary materials used in the production of the insulation are the flax fibres, polyester and diammonium hydrogen phosphate, accounting for 75%, 15% and 9%, respectively. Flax requires mostly virgin material for the initial production of insulation, but it is also a widely available renewable resource and quite recyclable . The use of farming equipment used in extracting flax from the fields is not an energy intensive process. A single tractor may be used to extract several tons of flax in a midsized field, which can produce a large quantity of insulation . Relative to other farmed crops, flax yielded the lowest output/input energy ratio (1.62 MJout/MJin) . The energy input into harvesting this material does not come near to that of extracting more dense raw materials such as metals and minerals.

Using of farming equipment such as tractors and tillers which run on diesel, large amounts of air pollutants such as CO, SO2 and NOx are produced and emitted into the atmosphere . On the other hand solid and liquid residues are quite negligible and if any occur they would mainly be due to oil leaks from equipment and replacement of wearing parts. Virtually all parts of the plant are used from the yield of flax fibres and straw to the shives and seeds of the plant . The roots are the only source of solid material left behind after harvesting. Flax seeds and tow are bi-products when harvesting for flax fibres, but these bi-products are used in different industries for things such as medicine and papers .

Manufacturing

Besides the main composition of ingredients which make up the majority of the insulations weight, there are also a variety of other small substances such as borax and even uranium, which contribute to the product of small amounts of hazardous waste. It is surprising to find out that manufacturing flax insulation requires a high level of fossil fuels, electricity and non-renewable fuels seeing how it’s a renewable resource itself. It requires 84 MJ/kg to hold the flax fibres to a polyester binder. Relative to stone wool, it consumes approximately 20 times more renewable energy. For these reasons flax deserves a ranking of 0 for its high energy requirements . When it comes to output residues in the manufacturing process, flax is not so great. It generates a very large amount of waste water during the retting process which is equivalent to 5 times the weight of flax being produced. A large portion of the solid waste produced is due to the machining process of sheets of insulation slabs. Flax also produces a large volume of CO2 due to energy production required for manufacturing from fossil fuels .

Packaging and Product Delivery

Packaging of flax accounts for about 1 kg for every 1000 kg of flax produced . The packaging is made out of high density polyethylene. Polyethylene requires the use of toxic chemicals in its production. Its manufacture requires 1.75 kg of petroleum in order to create 1 kg of high density polyethylene but it can be recycled and reused although the quality slightly decreases with remelting of the plastic . The method of transportation is by truck (flax is grown in Canada) which uses minimal energy compared to other alternatives such as by airplane or boat if distribution is required overseas. Once again the solid residues and liquid resides are similar to that of the pre-manufacturing stage where diesel powered tractors and various farming equipment is used for preparation of the flax.

Product Use

During the installation of flax insulation, workers who are constantly inhaling flax particles on a regular basis have been known to develop byssinosis or brown lung disease. Because the use of flax insulation is a relatively new product, this may be a problem to home owners in the future if exposed holes or leaks in the wall allow the insulation to release any forms of particulate matter . The insulation’s function is to reduce the amount of heat transfer through the walls this is a passive process and no energy expenditure is required. There are no gaseous residues which are emitted during the use of the insulation. However, solid particles of may be emitted this may be a health concern if loose flax particles are constantly being breathed in .

Recycling/Disposal

Although flax insulation can be recycled, the best method for disposal of the insulation is using incineration with energy recovery which can prevent 8% of the overall consumption of fossil fuels from being used . It might have been expected that land filling a renewable resource which comes from a plant (flax) would be the best method of disposal because it is biodegradable, but in fact it is in the worst method . The reason is due to the production of methane from the anaerobic degradation of the flax which heavily contributes to greenhouse gas emissions . The most energy consumption takes place in the disposal phase for flax insulation . Regardless of the different scenarios for disposal indicated in the sensitivity analysis, at least 80% of the insulation will be recycled which requires a total of about 50 MJ for every kilogram of insulation being disposed of . Few liquid residues are produced during disposal.

Cellulose Insulation

Pre-manufacturing

The main raw materials in the pre-manufacturing of cellulose paper insulation are 75% to 80% ONP (old newspaper), and retardant chemicals (borates and/or ammonium sulphates) . As a result of ONP availability, the score for material choice is high; although full marks are not earned since the chemicals used as fire retardant are “irritants”, and sulphate (SO4) in the ammonium sulphate compound can be the source of emission of sulphur dioxide (SO2) which can cause acid rain thereby impacting the environment . According to Hendrickson, used paper can emit methane (CH4) which is regarded as one of the greenhouse gases contributing in the emission of carbon dioxide (CO2) . However, the emission of such gases is low and almost negligible . In the paper-recycling process, energy is not extensively used because most of the waste removal, such as removal of ink and “stickies” (various adhesives used in printing), and removal of large objects such as plastic bags or cans, is done by flotation in mechanical cells. Water can be recycled, but solid wastes such as rejected ink must be land filled and are not recyclable. Chemicals used in de-inking and sticky-removal process are sodium hydroxide, fatty acid soap, hydrogen peroxide, a chelating agent, and sodium silicate .

Manufacturing

Recycled paper and fire retardant chemicals are manufactured in a closed-loop fashion and are reusable, and energy use in the manufacturing life stage is low, as cellulose having the lowest embodied energy of 1.75 MJ/kg, while mineral wool has the second lowest value of 15.1 MJ/kg . The process of manufacturing cellulose fibre insulation mostly involves emissions of solid residues such as residual particles. These particles are air-conveyed to the storage bin, and are not recyclable, but only small amount of these particles are emitted and no significant liquid or gaseous residues are emitted at this life stage .

Packaging and Product Delivery

A residential household described their experience with the installation of their cellulose insulation and they pointed out that the material used to pack the cellulose insulation was “non-biodegradable plastic” . The transportation means for cellulose insulation is by truck. The energy used to transport and install the material is similar to the manufacturing stage . There are some solid residues during the installation since cellulose is mostly loose-filled to the wall cavity, and the risk of exposure to dust and fire- or mould-resistant chemicals from loose-filled materials is high . No liquid and solid residues are emitted during transportation, but gaseous residues are considerably large from truck transportation.

Product Use

Although no further chemicals are added in the product use stage, the fire- and mouldretardant chemicals that were added in the product manufacturing stage can result in certain issues during the product use stage. For example, borates are water soluble and they leach out if the insulation gets wet, while another alternative, ammonium sulphate, makes metals corrode when they come into contact. Loose-fill insulation can also settle and reduce R-value as the result of the wind that brings dust and dirt to accumulate either by “compressing the insulation or by filling air pockets”. Fire and mould retardant chemicals may be hazardous if the cellulose insulation is not properly installed . If the insulation is exposed to excessive moisture then there could be mould build up at certain temperatures or the washing away of the fire retardant .

Recycling/Disposal

Cellulose insulation is land filled at the end-of-life stage. Even though cellulose insulation is produced from recycled newspaper, cellulose insulation is not recyclable. This is mainly due to the degradation of the paper quality after the paper recycling process . As discussed in the pre-manufacturing life stage, land fill of paper or paper

products results in the emission of the greenhouse gas, methane (CH4) . Truck transportation is used to transport cellulose waste to the land fill, hence low score on solid and gaseous residues.

Final results summarized for insualtion materials.

Economical Input-Output Life Cycle Assessment (EIOLCA)

An EIOLCA was performed on each of the three insulation alternatives. The EIOLCA software identifies all of the different economic transactions, environmental emissions and resource requirements needed for the production of a product or service in quantitative terms. This Life Cycle Assessment focuses only on the pre-manufacturing, manufacturing, and product use stages. The transportation and disposal stages of the product are not considered in this analysis. The method of transportation is very similar for all alternatives and along with the disposal stage they are both out of the scope of the EIOLCA.

Pre-manufacturing and Manufacturing

Rock Wool Insulation

The following table gives the general material composition for rock wool insulation .

Materials	Specific Materials	Total Percent Input (%)
First Set of Raw Materials	Igneous Rock Diabase Rock Gotland Stone Lime Stone Bauxite	71%
Second Set of Raw Materials	Industrial Waste Material (i.e. cement and steel production pre-stone wool waste post-stone wool waste)	21%
Binder	Phenol Formaldehyde Urea	8%

The raw materials of rock wool undergo many processes to form the final product. Once the raw materials are acquired through mining and recycled industrial waste (briquette production), they are melted and then cooled rapidly to form non-crystalline fibres . These fibres then go through a wheel centrifuge process to form spindle fibres, which enhances the properties of the material. For this LCA, it is assumed that binders are used to further enhance the mechanical properties of the product for insulation . It should be noted that the outputs at any of these manufacturing stages can be used as inputs into other sectors of the industry . For the environmental analysis, a producer’s price of $848,000 was calculated for 1000 houses and was inputted into the mineral wool manufacturing sector.

Flax Insulation

The following table gives the general material composition for flax insulation .

Materials	Specific Materials	Total Percent Input (%)
First Set of Raw Materials	Flax Fibres	65%
Binder	Polyester	15%
Other Chemicals	Borax, Ammonium Sulphate, Diammonium Hydrogen Sulphate	20%

Pesticides are required to maintain the good health of the flax plants against many insects and parasites such as grasshoppers and worms. Chemicals contribute to a large amount of material inputs, which are used within the manufacturing process to enhance the fire retardant properties of the flax plants. The producer’s price of flax insulation was $1,225,630, which was calculated for 1000 houses and was inputted into a hybrid sector with oil seed farming as the base.

Cellulose Insulation

The following table gives the general material composition for cellulose insulation manufactured by GreenFiber who claim to only use ONP (old newspaper) as raw materials .

Materials	Specific Materials	Total Percent Input (%)
First Set of Raw Materials	Newsprint (Cellulose fibre)	85%
Fire and Mould Retardant Chemicals	Boric Acid Ammonium Sulphate Zinc Sulphate Distillate Mineral Oil	<10% <11% <2% <1.2%

In this life cycle analysis, the raw materials are ONP (old newspaper), and retardant chemicals. After acquiring ONP, it goes into the recycling process in the pulp mills, which de-ink and remove sticky materials by flotation in mechanical cells; chemicals (i.e. sodium hydroxide, fatty acid soap, and hydrogen peroxide) are introduced in the pulper that make the ink and stickies become attached to the air bubbles and rise up to the top of the cell, and later removed as rejects . After the paper recycling process, recycled newspaper goes to the cellulose production process. According to the manufacturing process of cellulose insulation, recycled newspaper is size-reduced until cellulose fibers of 20 to 30 microns in size are obtained. Fire and mold retardant chemicals are then applied to the cellulose fibers, and the fibers are then dried and made ready for packaging and shipment . Similarly to flax insulation, the producer’s price of $1,503,580 was calculated for 1000 houses and was then inputted into a hybrid sector with oil seed farming as the base.

Comparison of Pre-manufacturing and Manufacturing Phases

For rock wool, the EIOLCA shows that the pre-manufacture and manufacturing stage involves a total of $1.69 million in economic activity, the production of 37.11 metric tons of conventional air pollutants, 1120 metric tons of CO₂ equivalent greenhouse gas emissions, 1670 kg of toxic releases, and uses 15.5 terajoules of energy. For flax, the EIOLCA shows that the pre-manufacture and manufacturing stage involves a total of $3.45 million in economic activity, the production of 59.08 metric tons of conventional air pollutants, 2664 metric tons of CO₂ equivalent greenhouse gas emissions, 3395 kg of toxic releases, and uses 35.8 terajoules of energy. Lastly, for cellulose the EIOLCA shows that the pre-manufacture and manufacturing stage involves a total of $3.34 million in economic activity, the production of 25.95 metric tons of conventional air pollutants, 1420 metric tons of CO₂ equivalent greenhouse gas emissions, 1980 kg of toxic releases and uses 19.3 terajoules of energy. These results show that rock wool has the least environmental impact out of all three alternatives since its values for greenhouse gas emissions, toxic releases and energy usage are the lowest of the three. When it comes to conventional air pollutants cellulose performs a bit better. Flax on the other hand finishes last in all categories and appears to be the worst choice in terms of environmental impact.

Environmental analysis of insulation materials.
Note: units vary accordingly.

Use

The lifetime use of each insulation material in a residential wall application is assumed to last for 50 years . To determine how much energy is saved in this phase, an in-depth approach was applied for each of the insulation materials.

For rock wool, equations that incorporated the conductivity and surface area of the insulation were used to determine the heat and energy lost through the material. Comparing this value to the average energy intensity required to maintain a certain temperature within a single detached home, the energy saved was calculated. Finally, this value was assumed to be contributing only to the savings of natural gas within a hot air furnace. This assumption was used to find the monetary value of natural gas saved over a life cycle of 50 years, which was $90,942,500 for 1000 houses. The same methods were applied for flax paper insulation and cellulose paper insulation.

For flax a value of $91,503,000 was obtained and for cellulose a value of $92,183,500 was obtained. Inputting these values into the natural gas distribution sector, a large amount of savings of conventional air pollutants, greenhouse gases, energy, and toxic releases were observed.

The largest contributors to conventional air pollutants were the VOC emissions. This came from the natural gas distribution sector. The amount of greenhouse gases saved was 202,500 MTCO2E over the use life cycle of the insulation. The major contributor was again the natural gas and distribution sector. The largest amount of energy savings came from pipeline transportation of natural gas, which was reflected in our original assumption of all the energy savings going into the amount of natural gas used to heat the house. The total amount of energy saved was 1260 TJ. The largest toxic releases were for land releases that came from the copper, nickel, lead, and zinc mining sector. It can be seen that all the savings are 10 to 100 times greater in magnitude than the amounts produced through the pre-manufacturing and manufacturing stages.

Cost Analysis

The direct costs for the insulation of 1000 houses was calculated using the material cost, the cost of power consumption during the pre-manufacturing and manufacturing stages, and the cost of power consumption during the use stage. The manufacturing facilities, and labour costs were considered similar for all the products, and therefore were not taken into account for this analysis. Maintenance and operation costs are considered negligible because the insulation is assumed to last the lifetime of the house being insulated, without being disturbed . The average Ontario electricity spot market price in 2007 was $0.051/kWh . This value was used to convert the power consumptions of the various stages into a monetary value. To calculate the indirect costs for 1000 houses only the air emissions were considered. In 2005, the economic cost for healthcare due to air pollution was $7,809,201,700 . The total amount of pollutants that Ontario emitted in that same year was 77.3 MT . These values were then used to calculate the air pollution cost factor (APCF), which was required to calculate the indirect costs. Therefore, the APCF = ${\begin{matrix}\left({\frac {\$7,809,201,700}{77,300,000tonnes}}\right)=\$101.03/tonne\end{matrix}}$. The indirect costs can be calculated using this factor multiplied by the amount of the individual emissions.

Direct Costs

Rock Wool

Material Cost = ($848.00/house)(1000 houses) = $848,000
Cost from Manufacturing Stage = $(15.5\times 10^{9}kJ){\begin{matrix}\left({\frac {1hr}{3600s}}\right)\left({\frac {\$0.051}{kWh}}\right)\end{matrix}}$=$219,583
Cost from Use Stage = $(1260\times 10^{9}kJ){\begin{matrix}\left({\frac {1hr}{3600s}}\right)\left({\frac {\$0.051}{kWh}}\right)\end{matrix}}$=$17,850,000
For a Use stage of 50 years: = $848,000 + $219,583 - $17,850,000 = -$16,782,417

Flax Insulation

Material Cost = ($1,352.39/house)(1000 houses) = $1,352,390
Cost from Manufacturing Stage = $(35.866\times 10^{9}kJ){\begin{matrix}\left({\frac {1hr}{3600s}}\right)\left({\frac {\$0.051}{kWh}}\right)\end{matrix}}$=$508,102
Cost from Use Stage = $(848\times 10^{9}kJ){\begin{matrix}\left({\frac {1hr}{3600s}}\right)\left({\frac {\$0.051}{kWh}}\right)\end{matrix}}$=$12,013,333
For a Use stage of 50 years: = $1,352,390 + $508,102 - $12,013,333 = -$10,152,842

Cellulose Paper

Material Cost = ($1,503.58/house)(1000 houses) = $1,503,580
Cost from Manufacturing Stage = $(19.28\times 10^{9}kJ){\begin{matrix}\left({\frac {1hr}{3600s}}\right)\left({\frac {\$0.051}{kWh}}\right)\end{matrix}}$=$273,133
Cost from Use Stage = $(1280\times 10^{9}kJ){\begin{matrix}\left({\frac {1hr}{3600s}}\right)\left({\frac {\$0.051}{kWh}}\right)\end{matrix}}$=$18,133,333
For a Use stage of 50 years: = $1,503,580 + $273,133 - $18,133,333 = -$16,356,620

Indirect Costs

Indirect costs are calculated using the sum of indirect costs from emissions of conventional air pollutants and GHG, where APCF = $101.03/tonne, and factor for ${\mbox{CO}}_{2}$ emitted is $16/tonne .

Rock Wool

Indirect costs of conventional air pollutant emissions = $3,749.21
Indirect costs of GWP = $17,920
Hence, total indirect costs of Rock Wool insulation = $3,749.21 + $17,920 = $21,669.21

Flax Insulation

Indirect costs of conventional air pollutant emissions = $5,968.86
Indirect costs of GWP = $42,624
Hence, total indirect costs of Rock Wool insulation = $5,968.86 + $42,624 = $48,592.86

Cellulose Paper

Indirect costs of conventional air pollutant emissions = $2,624.85
Indirect costs of GWP = $22,752
Hence, total indirect costs of Rock Wool insulation = $2,624.85 + $22,752 = $25,376.85

Societal Analysis

Rock Wool

The largest potential health effects occur during the installation phase of the product . The spread of dust must be prevented; otherwise it will enter the body through inhalation. During a short period of exposure, the substance will irritate the eyes, the skin, and the respiratory tract . Over a longer period, the substance will cause sore throat, laboured breathing, redness and itching of the skin and eyes . The insulation was originally thought of as carcinogenic, however in 2001, it was re-evaluated and is now considered as non-carcinogenic to humans . The following preventative measures should be taken when installing the insulation. A mask should be worn to prevent inhalation of dust particles, protective gloves and clothing are needed to protect skin, and finally safety goggles should be worn to prevent exposure of eyes to dust particles .

Flax Insulation

For flax, health problems such as byssinosis can be attained in the similar manner through the inhalation of flax particles during the installation of the material . Similar precautions must be taken by textile workers who install this material on a regular basis. In today’s society as environmental impacts on the Earth are becoming more of a concern people are looking towards more environmentally friendly solutions for today’s problems. Flax is a relatively new insulation product and the demand is still growing each year due to the awareness that it is an easily decomposable material when its useful life is over . Little do the public know that throughout the entire life cycle of flax, it is one of the least environmentally friendly alternatives. The problem is that the public generally don’t look at any other phase except the most obvious ones such as “recyclability after I’m done with it” and “what this product is made from”.

Cellulose Paper

Today's cellulose insulation concerns are primarily from the fluctuation of ONP prices , and problems caused by chemical additives ,. The cellulose insulation business became less substantial as cellulose insulation manufacturers dropped from 700 to about 65 during the 1970s and 1980s, and the ONP prices climbed up to 500% as the business rose again in 1994 . As cellulose insulation currently on the market competes with fibreglass insulation , cellulose insulation seems to be winning the market share according to Built Green Colorado due to the wake of green awareness in the society . Many studies have been done and shown that the both chemical additives used as fire or mold retardants (i.e. boric acid and/or ammonium sulphate) may irritate eyes and skin, and corrode metals in contact with the insulation .