- Cellulose Insulation
- Agricultural Fiber
- Spray foams (coming soon)
- Sheep wool (coming soon)
Division 7 – Thermal & Moisture Protection
There are several types of insulation addressed in this section that can be used in walls, floors, and ceilings.
Cellulose insulation is made from recycled newspaper and treated with fire retardants and insect protection. Borates, derived from the mineral Boron, are natural materials that can be used as fire retardants and insect repellents in cellulose insulation.
CFC and HCFC insulation refers to the blowing agents that contain chlorofluorocarbons used in making many rigid insulating sheathing products. Extruded polystyrene and polyisocyanurate foam insulation boards are currently made with CFC or HCFC blowing agents.
Agricultural fiber insulation is available in the form of cotton insulation made with mill waste, low grade, and recycled cotton. It is treated with a non-toxic fire retardant and comes in batts comparable to fiberglass insulation batts.
Cementitious foam insulation is made from magnesium from sea water and blown in place with air.
Perlite insulation is made from a natural occurring volcanic mineral and is often used as loose fill insulation in concrete block cavities.
Insulation materials play a primary role in achieving high energy efficiencies in buildings. There has been concern over the health impacts of the material constituents of insulation ever since the problems associated with asbestos became apparent, followed by the banning of urea formaldehyde based insulation. Some health concerns have spread to potential inhalation of fiberglass and cellulose insulation fibers and dust. Always wear a proper dust mask when working with these materials.
Cellulose insulation uses recycled newsprint that contains printers inks which can possibly outgas formaldehyde into a home. If there is any outgassing from inks, it should fall well below levels irritating most persons. However, an environmentally-sensitive person should be careful in selecting cellulose and install a vapor retarder between the insulation and the living space. (Note that the vapor retarder can exacerbate mildew problems if humidity levels in the house are high.)
There are also chemical additives often added to treat cellulose that are not thoroughly understood from an indoor air quality standpoint. Cellulose insulation that is treated with borates is preferred. Cellulose insulation can be bound together as a wet spray and installed in open wall cavities where it effectively seals the entire wall.
Rigid board insulations employed as sheathing on homes have played an important role in achieving high R-values. The use of CFCs in many of these materials has caused increased release of chlorine molecules into the atmosphere contributing to ozone depletion. HCFCs outgas a lesser amount of chlorine molecules. However, the severity of the ozone depletion situation has led to the recommendation to avoid both types of insulation blowing agent. Alternatives in rigid board insulation are available that do not use CFCs. (See Engineered Sheet Products section.) Any rigid expanded polystyrene insulation does not have CFCs.
Cementitious foam insulation is available commercially. There are no installers of this type of insulation in some regions. It is also more costly where available. This type of insulation is considered the most benign from an indoor air quality standpoint. Use installers who have a track record and can provide references.
Perlite insulation is in a loose form suitable to fill the cavities in building block. Perlite can be bound into other materials and used in sheet form. It is commonly used in commercial roofing material and can be used as an aggregate in concrete. It is non-flammable, lightweight and chemically inert.
Not listed is the use of rockwool insulation. Rockwool is recycled steel slag (a landfill material). It is available as blow-on wall insulation (a starch binder is used) and as loose blow-in attic insulation. It offers very good energy performance, will not burn, and is chemically inert.
Spray-in-place foam insulations are a fairly new addition. They offer the advantage of acting as a vapor barrier, effectively disallowing the cracks and gaps which can occur with rigid board or batt insulation methods. Some are made in part with soy oil instead of the more common petroleum oil, but it’s important to note that even the products with the highest percentage of soy oil still contain a majority of petroleum, and that the soy oil likely comes from genetically engineered plants which may be a negative in the view of some people.
Commercial wool insulation is available in limited areas. Being made from a naturally produced fiber, sheep wool insulation typically requires less than 15% of the energy required to produce than glass fiber insulation. Wool is a sustainable and renewable resource, that has zero ozone depletion potential and at the end of it’s useful life can be remanufactured or biodegraded. Sheep wool insulation is safe and easy to handle and no protective clothing or special breathing apparatus is required to install it.
|CFC / HCFC|
|Cellulose w/ Borates|
|Satisfactory in most conditions|
|Satisfactory in Limited Conditions|
|Unsatisfactory or Difficult|
Well-developed and changing. More recycled-content types are being developed. Cotton insulation is new.
Adequate for cellulose insulation; new suppliers for cotton insulation are currently being established. Cementitious foam requires trained installers. Perlite and rockwool are available. Spray foams are becoming more common.
COST: (varies by region)
Prices can vary according to installer.
Cellulose/cotton/fiberglass insulation: less than $.20 per square foot for R-19 uninstalled.
Wet blown cellulose insulation: 50% more installed.
Air Krete: $2.00 per square foot for 2√ó6 walls installed.
Perlite (as loose fill): $5.00 to $8.00 per 4 cubic feet.
Rockwool: $0.50 per square foot installed in 2 x 4 wall, comparable to cellulose in attic
The general public is mostly unaware that CFCs can exist in insulation. Cellulose insulation and spray foam is commonly accepted. Cotton insulation is attractive to environmentally-aware individuals and those doing their own insulating work as it will not cause skin irritation. Perlite insulation is relatively unknown to the general public. Cotton and perlite are not likely to be negatively perceived. Rockwool and sheep wool are relatively unknown as a modern insulation option.
Must meet flame spread and smoke density requirements, listed in Section R-217 of the CABO One and Two Family Dwelling Code.
1.0 Cellulose insulation
As a loose fill material applied in attics, install baffles to keep the material away from soffit vents. The baffles will also prevent wind from the soffit vents through blowing the insulation. Don‚Äôt cover recessed light fixtures unless the fixtures are certified to accept insulation.
Cellulose insulation can be effectively used in wall cavities in new construction. As a dry loose-fill wall insulation, it could settle.
Wet-blown insulation offers superior insulating qualities and can be trimmed by hand on walls before installing drywall. Moisture control is critical with wet-blown insulation as overly moist insulation requires a longer drying period before a wall can be closed up. Wet blown insulation offers excellent performance.
CFCs or HCFCs are found in extruded polystyrene foam boards, isocyanurate foam boards, phenolic foam boards, and polyurethane blow-in insulation.
Expanded polystyrene rigid insulation at a higher density of 2 lb./ft3 (normal density is 1.0 lb./ft3) performs similarly to extruded polystyrene. Expanded polystyrene does not contain CFCs or HCFCs. It typically uses pentane as a blowing agent and has some recycled content.
(See the Engineered Sheet Materials section for alternative insulating sheathing materials.)
3.0 Agricultural fiber
Cotton insulation comes in batts and is installed in the same manner as fiberglass batts. The material should not be compressed when installed in order to retain its full insulating qualities.
It is treated with borates as fire retardant.
4.0 Cementitious foam
This insulation is fire proof, insect proof, and non-toxic.
Trained installers must be used. The material expands as it sets and can crack walls if installed incorrectly.
The material contains a lot of water and will need a drying period before a wall can be closed up.
The material is friable (easily crumbled) when dry.
Can be used in concrete to make an insulating lighter weight concrete.
Predominantly used as a pour-in loose-fill in cores of concrete block.
5.1 Loose fill installation location and method
Must be installed in sealed spaces:
Cores of exterior (and interior) hollow core block;
Cavity between exterior (and interior) masonry walls;
Between exterior masonry walls and interior furring.
Rockwool is manufactured in Texas, Washington,North Carolina and Indiana.
It is made comprised of steel slag ( over 75%) with some basalt rock ( 25% or less). In some plants the recycled steel slag makes up almost 100% of the content.
Blow-on application will seal wall cavities similarly to wet-blown cellulose offering superior insulating service compared to batts.
It is installed in attics in a loose fill blown form that goes in at a rate of 1.4-1.8 pcf , while the side wall spray is installed at a rate of 4-5pcf. With theses densities the slag wool has better STC ratings and R ratings when compared in exact designs with the otther cellulose and fiber insulation products.
Weighs more than fiberglass (rockwool is 1.2 pounds per square foot for R-30 versus 0.5 pounds for fiberglass). It is less likely to become airborne.
Rockwool is the only insulation that will stop fire.