insulation

If your house is much more than 10 years old the odds are that it probably doesn't have as much insulation as it needs in order to be energy efficient.  Most U.S. homes were built at a time when energy was cheap and when building codes did not mandate significant insulation.  For this reason evaluating your home insulation is usually one of the best places to begin if you want to reduce your energy bills.

Most home insulation is installed using either batts which are designed to fit between wall and ceiling joists, or as loose fill which can either be hand poured or blown in using an insulation blower.  Loose fill insulation is often the only option for side wall insulation since batts could not be installed without tearing down the walls.  Loose fill can be blown in through holes drilled in either the interior or exterior walls. 

Types of Insulation

Fiberglass - Most of us are familiar with the large pink blankets or batts of fiberglass insulation (remember the Pink Panther logo).  This continues to be a very effective form of insulation for attics and roofs.  Manufacturers now produce a higher density fiberglass that provides even greater R-value then earlier types. Fiberglass is well suited to the do-it-yourselfer. The batts are designed in widths that fit easily between most attic joists and are easy to install. A high density batt for a 2 x 6 inch frame wall provides an R value of 21. Thicker batts can easily to R values of 30 or better.

Fiberglass can also come in a loose pace form designed to be installed with an insulation blowing machine. This type of insulation will work well in spaces where the framing is not conducive to batt style insulation. This type of fiberglass insulation can provide R values that are as good if not better than the fiberglass batts.

Cellulose - Cellulose insulation is a type of loose fill insulation made from recycled wood fiber, usually newsprint.  Cellulose has a thermal resistance of about R-3.6 to R 3.8 per inch.  One disadvantage of cellulose is that it absorbs more water than fiberglass or rock wool.  Most cellulose is treated with chemicals to make it more fire resistant.

Rock Wool - This is a type of loose fill insulation, also referred to as mineral wool, is made by melting and spinning rocks such as basalt into a fiber. It has a thermal resistance of about R-3.7 per inch. Because it is made of rock it is naturally fire resistant and has a good R-value comparable to cellulose and other types of loose fill.  Some manufacturers also make a batt form of rock wool for those who prefer its ease of installation.

Plastic Fibers - Like cellulose the plastic fibers are usually made from recycled material, most often recycled plastic milk bottles. It is usually made into batts like fiberglass and has an R-value of 3.8 per inch.  The batts are usually treated with fire retardant but they will melt when exposed to flame.

Natural Fibers - Several types of natural fibers can be employed for insulation.  Cotton, often made from recycled blue jeans, can be used as a type of loose fill insulation. The cotton fill is often mixed with plastic fibers that have been treated with borate to make it more fire resistant. It has a thermal resistance of about R-3.4. Wool too can be used for insulation and has a slightly better R value.  It also is treated with a fire retardant.

Straw Bales - Sometimes everything old is new again.  One type of insulation that is making a resurgence in the U.S. are hay bales.  Hay bales were used both as construction material and insulation in the plains in the 1800's because wood was so scarce.  People have started looking to it again because it has a number of advantages.  Hay bales, which are just compressed straw, have a very good R value (at least 2.4 - 3.0 per inch).  The compressed bales have proven to be very fire resistant, especially when they are packed with adobe or plaster.  They also have the advantage of being a recycled agricultural material which is readily available in most locations. Straw bales, however, do have standard dimensions which are usually much thicker than used in traditional wall construction.  Consequently they are something to consider when doing new construction but are probably not practical for most existing home owners.

Concrete Blocks - While we tend to think of concrete blocks as a construction material there are now many types of concrete blocks available which come with insulation built into them.  Sometimes this can be a fill type of insulation which goes in the hollow of the block such as polystyrene beads.  Some blocks use a rigid foam insert instead.  This approach can bring up the R-value of a concrete block to about 2.0 per inch.

Autoclaved Aerated Concrete (AAC) - Another type of concrete that has recently become available in the U.S. is what is known as autoclaved aerated concrete (AAC),  In this type of concrete air makes up as much as 80% of the volume of the material.  The material is extremely light compared to conventional concrete but has ten times the insulating capacity. The material is more like a foam block in many ways and can be shaped, cut and sawed which makes it easy to fit into many types of spaces.  The one disadvantage is that it will absorb moisture because it is more porous and should always be used in combination with a vapor barrier.