If you are considering insulating the walls of your old house there are several things to consider before you get started on this home improvement project: how your house was constructed, the type of blown-in insulation, if you are up to the challenge of doing it yourself or will you need to hire someone to do it, and the possible negative aesthetic impact. This energy conservation method can easily save you hundreds of dollars every year on your heating and cooling bills, but it’s a bit more involved than adding a layer of "pink" in your attic.

First you must examine how your house was built. If you have solid masonry walls of brick, stone and/or clay masonry units you really should not add any insulation. The second red flag to look for is if your house has "knob and tube wiring." If so, it must be removed and replaced since covering this type of wiring with blown-in insulation is a fire hazard. If your house was built in or before the 1950’s it may be "balloon framed" instead of "platform framed" which means that the cavity between the wall studs will extend from the top of the foundation wall all the way up to the roof rafters. These cavities are obviously interrupted by doors and windows, but they are not interrupted by floor framing as is the case with "platform framing." The implication here is that with balloon framing fewer holes will need to be drilled into your walls.

The three most common types of blown-in insulation are: cellulose, fiberglass and foam. Each type has its positives and its negatives. Cellulose insulation is basically recycled ground up newsprint that has been mixed with chemicals that deters mold, fire and vermin. This is typically going to be your least expensive option and is a little better than fiberglass at preventing water damage in your walls. One drawback of cellulose insulation is that it will not fully fill the inside of the wall cavities as it will not expand like foam into cracks and around obstacles in the wall. Furthermore, it can settle a little over time leaving small gaps of no insulation at the tops of your walls. This however can take many years to happen and is most often insignificant. Fiberglass is one of the most familiar types of insulation. This solution will usually be a little more expensive than cellulose and its insulating capabilities are slightly less effective. It is less likely to settle than cellulose, but only contains about half of the recycled content. Foam insulation is by far the most effective energy conservation improvement for your walls. Foam will completely fill the entire wall cavity and any minor cracks and openings, this creates an effective air barrier that will seal any source for air leakage. The basic insulating properties of foam are about 33% better than cellulose and 60% better than loose fill fiberglass. However, overall foam performs even better because of its air barrier qualities. The only drawback to foam is cost, only you can decide if the added savings will be worth the added cost.

The blown-in insulation of choice for the do-it-yourselfer is cellulose. The materials and equipment for installing cellulose insulation can be found at most large home improvement stores, but you should have some general knowledge of wood framing and other home improvement skills. If you do decide to take on this challenge make sure to plan carefully and take all safety precautions including using dust masks. You could blow fiberglass into your attic yourself fairly easily, but leave it to the professionals to blow it or foam into your walls. The materials and equipment for installing foam insulation are not typically available to the general public.

Finally, the last consideration is how this project may impact the looks of your house. Many blown-in insulation contractors will prefer to drill holes directly through your siding or stucco into the wall cavity and repair them at the end of the job by placing a painted plastic plug into the hole, this will be your least expensive option, but it will have a negative impact on the look of your house. A second option is to carefully remove the siding in the required locations, drill holes through only the sheathing, install the insulation, plug the holes and then replace the siding. This solution will be more expensive and may require you to repaint your entire house, but it will leave your house looking just as before. One complication is that some sidings are very difficult if not impossible to remove without damaging them. Homeowners with brick or stone veneer do not have the option of insulating from the exterior and must do it from the inside. This solution, available to everyone, creates a bit of a mess in your house, but drywall and plaster is much easier to patch and repair without leaving a trace.

Regardless of which options you choose, adding insulation to your home is one of the most cost effective energy conservation strategies that you can use to reduce your heating and cooling bills. Depending on the efficiency of your heating and cooling equipment and the cost of energy in your area insulating the walls in your older home could pay for itself in as few as two years or as many as ten. However, if viewed as an investment, insulating your older home is one of the best and safest that you could make, returning you a 10% to 50% return on your investment, and that is with today’s energy costs.