Wall Insulation

How To Choose The Proper Wall Insulation

Choosing inadequate wall insulation can be a costly mistake. The house will be either too cold in the winter, or keeping the temperature warm enough will result in higher than necessary heating bills. While wall insulation is installed with the idea of keeping the cold out, adequate insulation can also help keep the interior of a house cooler during very hot weather, and cut down on air conditioning costs. The other expense to bear in mind, is the cost of tearing out drywall to install new insulation in exterior walls. Although not normally its primary purpose, wall insulation can also make for a quieter house, cutting down street noise, and in some instances can even make it harder for insects to find their way into the interior of the home.

A Number OF Different Types Of Insulation - Wall insulation can come in a number of forms or materials. The most common types are batt and blanket, which are usually cut to standard widths, to accommodate walls having, for example, 18" of separation between the studs. Rather than being cut to a standard height, though possible, batts and blankets are usually purchased by the roll, with the installer cutting them to accommodate the height of the wall. Fiberglass and rock wool are the materials usually found in batt and blankets.

Blown insulation is also commonly used, though is normally used in attics or cavities having significant depth or volume. Applying blown insulation between wall studs is not particularly practical, though not impossible to do. A better choice would be an extruded polystyrene, or polyethylene foam. The latter two types would be significantly more expensive than the blankets or batt, but offer up to double the insulation value per inch of thickness. An advantage of foam insulation is that it can be blown in to cracks and crevices, such as may be found around doors and windows, where blankets or batt may allow cool air to enter in some cases.

The R-Value Is The Key - When purchasing insulation you will note that the material is given what is called its R-value. The R-value is a measure of the material's resistance to allowing cold to pass through it, and is calculated based upon the physical characteristics of the material and its thickness. For example, a one-inch thick rock wool batt will have an R-value of around 3.5. A two-inch thickness of rock wool would have an R-value of 7. For comparison, a one-inch thickness of polyurethane foam has an R-value of 6.25 and a 2-inch thickness has an R-value of 12.5.  When you buy a roll of batt or blanket, typical R-values shown on the covering might be R-15 or R-21.

Where You Live Makes A Difference - The value you would want to purchase will depend upon where you live. For simplicity, the R-value required for exterior wall insulation in Alaska would be significantly higher than required for a structure in southern California, or Arizona. Building centers will usually stock wall insulation having the appropriate R-value for their particular locale, and in fact will often offer 2 or 3 different types or thicknesses of insulation with correspondingly different R-values.

Many Things To Consider - The distance between studs on an exterior wall also influence the R-value you would need. There are on line calculators which can either be used interactively or downloaded, to help you in determining the exact R-values required for a particular application. While there can be a number of things you need to know to do a proper job of installing wall insulation, it really isn't all that complicated, particularly if you don't let yourself be intimidated by talk of the R-value. Learn what it's all about, then you can intimidate or impress others.