Fiberglass batts are the insulation system that all other insulation systems compare their insulation to. Fiberglass was developed in the 1930s by accident when pouring glass. It is made out of sand and by heating the sand, turning it into glass, and then forcing it through very small holes in a plate. Recycled glass is commonly used in the making of fiberglass to varying amounts, one company is guaranteeing 60% recycled. The fiberglass fibers are then made into batts using adhesive to hold the fibers together. The most commonly used bonding for years contained formaldehyde. Formaldehyde has been labeled a “probable human carcinogen” by the International Agency for Research on Cancer (IARC). This chemical off-gasses and can contribute to poor indoor air quality. Most insulation manufacturers have stopped using formaldehyde in their products and now use some type of acrylic binder. These adhesives on the fiberglass fibers are what make most fiberglass itchy to install. There are other types of batts out there but they all have the same installation issues.
Fiberglass batts have been used for many years as the standard type of insulation in residential uses for many years. A variety of facings are available or none at all. The batts come in different densities and usually 16 or 24 inch widths. R value for batts is R 2.9 to 3.8. A big selling point of batt systems is the homeowner can do it themselves. The biggest drawback to fiberglass batts, or any type of batts, is in the installation. The key to batts is to fill the cavity to the correct density. If the installers are very careful voids or batt compression can be kept to a minimum. It is difficult to fit batts around wires or plumbing and into the complicated shapes and sizes of wall framings. If the cavity is not full or there are voids in the insulation you are losing R-value. In the real world study after study has shown that it is very difficult to get a good installation using batts. Thermal imaging is on the increase and it shows all the bad spots in an installation. New Energy Star regulations require a Grade 1 insulation system and it is very difficult to get batts installed to this level. Safety equipment normally used is a dust mask, gloves and long sleeves.
Blow-in-Blanket System (BIBS)
The Blow-in Blanket System (BIBS) is fiberglass insulation taken to a higher level using the best qualities of the fibers. All insulation systems are compared to fiberglass batts. None are compared to the Blow-in-Blanket System. The fiberglass fibers are engineered to be blown into a cavity behind netting filling the cavity to a uniform density no matter what the shape. R value is 4.2 per inch. Using pure fiberglass with no adhesives it is inert and can be reused. BIBS does not support mold, insects or rodents. It does not absorb moisture and it does not burn. There is no off-gassing. By filling voids as well as it does sound suppression is very good. A BIBS installation does not settle and it is the only insulation system in which regular testing throughout the installation is done to ensure the correct density of the final product thereby ensuring the 4.2 R value.
The installation of the Blow-in-Blanket System is what mainly sets this insulation apart from any other system. Polypropylene netting is stapled tightly over the cavity. A hole is then poked in the netting, the hose inserted, and the cavity is filled. By blowing in the fiberglass the cavity is custom filled to the correct density by BIBS trained installers. Another higher level is attained by BIBS installers belonging to the Blow in Blanket Contractors Association (BIBCA). A BIBCA member has regular training to insure the proper installation of the system. By being a BIBCA member in good standing the fiber manufacturers will warranty the Blow-In-Blanket System insulation for the life of the building. BIBS in 2x6 construction equals R-23 and in 2x4 it is R-15 which is about as much R value as is currently available in that cavity depth. The installation is clean as the netting contains most of the fibers. Safety equipment is a dust mask, though there is very little dust. The fibers are pure fiberglass with a texture like cotton balls so it is not itchy like most fiberglass batts. The Passive House Institute US founder Katrin Klingenberg calls blown in fiberglass the most cost effective insulation. BIBS cost is typically 30% to 50% more than fiberglass batts, though this cost is a higher R-value also, and again, it fills the cavity much better.
Blown in fiberglass using the smaller fibers is also very effective in dense packing existing walls. 2.25# of fiberglass has the same or less air infiltration as cellulose, which is the other commonly used dense packing material. The fiberglass is a higher R-value and doesn't have to be packed in so tightly as cellulose, so there is very little risk of blowing sheetrock off the wall.
One of the considerations with all insulation systems that is now being looked at is Global Warming Potential, (GWP). Fiberglass GWP is higher than cellulose but less than foams. The GWP is somewhat offset because fiberglass can last a very long time, is up to 70% recycled glass, and can be taken out of one home and put into another if desired.
Cellulose insulation is ground up newspaper, cardboard and paperboard that is finely shredded and then treated with fire retardants and mold inhibitors such as boric acid, sodium borate and ammonium sulfate. It is about 80% recycled material by weight. There has been some concern in the past about the chemicals in the cellulose itself combined with the retardants that it could create corrosion problems with some materials in a wall cavity. The fire retardants can be applied to the ground up paper as a powder or a wet spray that is then dried. If the cellulose has powdered retardants in it they sometimes separate in the insulation blower and leave residue. Cellulose is a dusty insulation to install and the powdered retardants seem to be dustier. Manufacturing cellulose is a low - tech process and there are 20 some companies making it in the US. Cellulose absorbs water and can be hard to dry. Wet cellulose loses a lot of R value and can lead to mold problems in a cavity. There has also been a lot of concern about cellulose coming into contact with hot surfaces in a cavity like lighting fixtures and then igniting causing a fire.
Installation of cellulose is done dry behind netting in walls or wet sprayed into a cavity. It has also been blown into existing walls and other cavities claiming it will air seal if it is dense-packed. It has been observed that in some cases dense-packed cellulose has settled in walls. Quality control is difficult. When blown in behind netting care has to be taken to get enough density to prevent settling, which can then make it hard to install sheetrock because of bulging insulation. The wall cavity should be made to keep the cellulose dry. Cellulose installed in a wet spray uses a small amount of water, possibly with adhesive, to hold it into the wall cavity. The cavity is over filled and then a scrubber is used to shave off excess material outside the cavity and then the cellulose has to be dried down to a low humidity to prevent mold or, if the humidity is too high, it can affect structural integrity. Controlling the amount of water mixed with cellulose is an industry problem. This is the major problem with wet spray cellulose. Cellulose has an R value of 3.1 to 3.7 per inch. In a 2x6 cavity R- 20 is possible.
The GWP of cellulose is the lowest of commonly used insulation. Except for the fire retardent chemicals, cellulose has been recycled paper and cardboard. Newsprint was a major component in cellulose, but everyone knows there is not as much newsprint as there used to be. Unused or new paper has been used to make some cellulose, which increases GWP. Lifespan of cellulose is pretty long, but how long depends on the environment it is in.
Polyurethane foam is a closed cell foam. Polyurethane is a petroleum product using urethane , resin and different blowing agents. When sprayed into a cavity the foam expands, filling the cavity to a desired depth. The foam adheres to most building products and hardens which adds a small degree of structural strength to the cavity. It does not require a vapor retarder and acts as an air barrier. Low conductivity blowing gas is normally used as a blowing agent to make the foam expand. The downside to this is the gas is normally a CFC or HCFC gas, although companys are working hard to change this. These gases bleed off and as they do it lowers the R value and can be an air quality issue. The foam usually stabilizes at R-6 or R-7 per inch. Check with your installer to verify what the cured R-value will be. Closed cell foam does not support mold or insects or rodents. It is not recyclable. Polyurethane foam is like other foams in that it is not easy to get to burn but when it does it gives off thick black smoke and various toxic gases.
Installation of polyurethane foam is done by licensed installers. There are differences in the manufacturers ingredients and other variables in the application. No one else should be in the area when spraying foam and the installers have to wear respirators and protective clothing to keep the foam off. The area should also be vented to remove gasses. OSHA and NIOSH have lately done studies showing significant asthma hazards from the isocyanate used in polyurethane. Up to 30% of workers in production plants that use polyurethane have isocyanate-induced asthma. This can be transmitted by breathing or direct contact. Some people are sensitive to the foam gasses and can't have it in their home. Unfortunately, the only way to find out is to go or live in a foamed home. Once the foam has expanded and hardened it can be cut easily if need be. The foam is then left to gas off for a period of time. Polyurethane foam is usually installed to a depth of about 3 inches, about R-18 to R-21, in a cavity mainly because it is expensive to fill a deep cavity. This 3 inch depth can be hard to achieve without overfilling the cavity which could affect cost.
Installer experience is needed to get the right mix of chemicals at the right depth and at the right temperature of installation. Installation temperature is critical or the foam will not stick to the surface it is being blown onto. The installation also has to be done in the right way as in how much is sprayed in at one pass. Spraying foam is a chemical reaction, which means it makes heat. There have been incidences across the country of buildings burning down because the foam was not installed properly, it got hot, and it started a fire. Some building scientists do not like the practice of blowing closed cell foam into a cavity and not filling it. This can lead to moisture issues in the wall and also makes the wall assembly less effective due to wood conducting the cold through the wall. Best practices is to fill the wall cavity with insulation. The major drawback with this foam is the cost and the complexities of installation. Because it is a petroleum product the price is connected to the price of oil, and this is the costliest insulation commonly used.
The GWP of foam is high. It is also uncertain how long it will last in a home. The industry does accelerated aging tests, but in the real world it can be different. Closed cell foam can not be installed in a closed cavity, like an existing wall.
Open Cell Foam
Open cell foam is a foam that will allow water vapor to travel through the cells. This means in a cold climate a vapor retarder will be required. Urethane foam mixed with different resins are mixed similar to polyurethane foam, but the expansion rate of the foam is higher than closed cell foam and the blowing agent is carbon dioxide or water. Most open cell foam also has isocyanates in it which, according to OSHA and NIOSH, increases the risk of asthma by breathing or touching the foam. Icynene foam is a widely marketed example of open cell foam. This foam expands at about a 100 to 1 ratio using water as a blowing agent. This expansion fills the cavity creating an air barrier reducing air infiltration and it adheres to most building products. It does not react to wires or pipes normally found in cavities and does not support mold, insects or rodents. Open cell foam is softer than closed cell foam so does not improve structural integrity which really should not matter anyway. Open cell foam has a good fire rating and does not absorb water. Icynene foam claims an R value of 3.6 per inch which in a 2x6 cavity would be R-20.
Installation of open cell foam is done by licensed dealers. The installer blows the foam into the cavity which expands rapidly which should fill the cavity. The foam projects out from the cavity and is then cut off flush with the studding, and vapor retarder installed if needed. Any voids in the foam should be refilled. Like closed cell foam, the installation makes heat. The installation can be messy so covering objects to keep over spray off and cleanup are part of the project. The installer uses a respirator and protective clothing and it is claimed the foam is cured very shortly after installation although there is some odor. Again, some people are sensitive to the chemicals in the foam. Open cell foam in a cold climate by code has to have a vapor retarder.
The GWP of open cell foam is high. It is a petroleum product. How long will it last? Like all foam, there have been accelerated aging tests. The problem, also like all foams, is that the companys are tweaking the chemicals a lot to change the foam for one reason or another.
Bio foams are foams using a soy based product used to replace some of the petroleum products used in open and closed cell foam. Up to 75% bio foam is used in these foams, though most are much less. They have most of the same properties as open and closed cell foam although there is some claim that because of the soy based product it has the potential to support mold because it provides food for the mold. Bio foam also uses what could be food to make foam. Installation is the same as for the other foams with the same safety equipment, with the same safety hazards.
GWP is high with Bio foam. It still has petroleum in it. Longevity is the same as other foam.
When comparing all of these insulation systems to each other looking at the raw material, the manufacturing process, ease of installation, installation process, and environmental impact some things start to become clear. This cradle to grave life cycle assessment is being done now on more and more products and fiberglass looks very good in these assessments. Throw in R- value, cost and final performance and it is clear that the Blow-in-Blanket System is the best combination in most circumstances. There are small places in almost any home where some of these other types of other insulation can be used that would maybe be better than BIBS. However, BIBS has the right cost, R-value per cavity, environmental impact, and ease of installation to be a clear best choice. This is why the Passive House Institute calls blown in fiberglass the most cost effective insulation system.