Insulating the walls of your old house

If you’re considering insulating the walls of your old home, there are several things to consider before beginning this home improvement project: how your home was built, the type of insulation blown in, whether you’re up for the challenge of making it yourself or you will need to hire someone to do it, and the possible negative cosmetic impact. This energy conservation method can easily save you hundreds of dollars each year on your heating and cooling bills, but it’s a little more involved than adding a layer of “pink” to your attic.

You must first examine how your house was built. If you have solid masonry walls of brick, stone, and/or clay masonry units, you really shouldn’t add any insulation. The second red flag to look for is if your house has “knob and tube wiring.” If so, it should be removed and replaced, as covering this type of wiring with blown insulation is a fire hazard. If your home was built in the 1950s or earlier, it may have “balloon frame” instead of “deck frame,” which means the cavity between the wall studs will extend from the top of the foundation wall to ceiling joists. These cavities are obviously interrupted by doors and windows, but are not interrupted by floor frames as is the case with the “platform frame”. The implication here is that with the balloon frame fewer holes will need to be drilled in the walls.

The three most common types of blown insulation are: cellulose, fiberglass, and foam. Each type has its positive and negative aspects. Cellulose insulation is basically recycled shredded newsprint that has been mixed with chemicals that prevent mold, fire, and vermin. This will generally be the least expensive option and is slightly better than fiberglass for preventing water damage to walls. One disadvantage of cellulose insulation is that it will not completely fill the interior of wall cavities, as it will not expand like foam into cracks and around wall obstructions. Also, it can settle a bit over time leaving small, uninsulated gaps at the top of walls. However, this can take many years to happen, and in most cases it is negligible. Fiberglass is one of the best known types of insulation. This solution is usually a bit more expensive than cellulose, and its insulating abilities are slightly less effective. It is less likely to settle than cellulose, but it only contains about half the recycled content. Foam insulation is by far the most effective energy conservation upgrade for your walls. The 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 of air leakage. The basic insulating properties of foam are approximately 33% better than cellulose and 60% better than loose-fill fiberglass. However, foam in general works even better due to its air barrier qualities. The only downside to foam is the 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. Materials and equipment for installing cellulose insulation can be found at most large home improvement stores, but you should have a general knowledge of wood framing and other home improvement skills. If you decide to take on this challenge, be sure to plan carefully and take all safety precautions, including wearing dust masks. You could blow fiberglass into your attic yourself quite easily, but let the professionals blow it or foam your walls. The materials and equipment to install foam insulation are not normally available to the general public.

Finally, the last consideration is how this project may affect the look of your home. Many blown insulation contactors will prefer to drill holes directly through the siding or stucco into the wall cavity and repair them at the end of the job by putting a painted plastic plug in the hole; this will be the least expensive option, but will have a negative impact on the appearance of your home. A second option is to carefully remove the siding at the required locations, drill holes just through the siding, install the insulation, plug the holes, and then replace the siding. This solution will be more expensive and may require you to repaint the entire house, but it will leave your house looking like it was before. One complication is that some coatings 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 outside and must do so from the inside. This solution, available to everyone, creates a bit of a mess in your house, but drywall and plaster are much easier to patch and repair without a trace.

Regardless of the options you choose, adding insulation to your home is one of the most cost-effective energy conservation strategies you can use to lower your heating and cooling bills. Depending on the efficiency of your heating and cooling equipment and the cost of energy in your area, the insulation in the walls of your older home could pay for itself in as little as two years or as long as ten. However, if considered an investment, insulating your old home is one of the best and safest things you could do, giving you a 10-50% return on your investment, and that’s with the costs of current energy.