Beef Up Your Old Insulation without Tearing into Walls

■ BY JUSTIN FINK

hen it comes to insulating floors, walls, and ceilings, nothing makes it easier than working with the blank canvas of a newly framed house. The walls are wide open, so contractors can add any type of insulation they want to achieve the best pos­sible thermal performance.

What about the rest of us, though? Those of us living in houses built with minimal
insulation, or none at all? The ones who don’t have the luxury of gutting their walls? The ones who work on or live in houses that hemorrhage heat in the winter and bake like an oven during the summer? What can we do to improve the thermal performance of these homes?

A lot. Techniques and materials for retro­fitting insulation in old walls have improved

over the years. Many times, insulation can be added from the interior or exterior of the house without gutting the walls. Even so,

I’m not going to sugarcoat this: Adding new insulation to closed walls is a hassle.

Pick the Low-Hanging Fruit First

Before thinking about adding insulation to your walls, you should have already tackled your home’s other major weak spots. If you haven’t, you should, and your efforts should begin in the attic, where the most heat loss typically occurs (see "Upgrade Your Attic Insulation," pp. 46-55). If, however, after air-sealing and insulating the attic and plug­ging some other common energy trouble spots (see "Home Remedies for Energy Nosebleeds," pp. 12-19) your house still feels drafty and your energy bills are still too high, it’s time to consider the walls.

There’s a lot to consider when it comes to adding new insulation to old walls. The first step is to find out what type of insula­tion, if any, is already in the walls. Once that is determined, you can assess the thermal performance of the walls and then make a more informed decision about the potential benefits of an insulation upgrade. You might
find that the existing insulation is astonishingly inferior and that a small out­lay of cash would mean a significant decrease in your energy bills. Or you could be surprised to find that a high-cost retrofit will offer only a minuscule return on investment.