REAL ESTATE- GIMME SHELTER- Drill n' Fill: Retrofit insulation for that old house

Ned Ornsby
Project Manager, Lithic Construction


Q: We own a city home built in the mid-1960s that has little or no insulation. We'd like to make the house more energy efficient, but don't know what the options are. Isn't the some kind of new insulation you can inject into the walls?

A: Yes, there are several blown-in and sprayed-in products available, the most common being fiberglass, cellulose, and foam. And they can save you alot. Considering the fact that around 50 percent of the money you spend operating your home is for heating and cooling, the 30 percent or more you can save by retrofitting insulation into your existing walls is nothing to scoff at.   

Known as "drill and fill" insulation in the construction biz, the process involves injecting fiberglass, cellulose, or foam insulation directly into your walls or attic through a tube, either by drilling holes in your siding or walls, or by removing sections of each. Attics are a little easier– insulation can simply be blown through the attic door or crawl space opening. While blowing fiberglass or cellulose into an attic can be a job for do-it-yourselfers– you can get bails of cellulose at Lowe's and rent a blower– it's probably best to consult a pro for retrofitting walls, especially if you decide to use foam. 

While fiberglass and cellulose (cellulose is made up mostly of recycled newspapers and treated with chemicals to be fire-resident and deter pests ) will definitely improve  energy efficiency, foam products tend to work better. There are a variety of foam products on the market, but one called Aircrete, a cement magnesium oxide foam, has proved to be the best we've seen. 

Aircrete has the consistency of shaving cream when it's applied, and works its way around obstacles to fill every small hole or crevice. Basically, it fills the wall space the way water would fill a fish tank. Fiberglass or cellulose work the same way, but they can leave voids and gaps around things like pipes and wiring. The foam then begins to set in about an hour and eventually becomes as hard as a very light-weight concrete, creating an impermeable air barrier which has a higher energy-saving "R" value than fiberglass or cellulose, in addition to being non-toxic and fire, mold, and pest-resistant.

Of course, having aircrete installed is more expensive than fiberglass or cellulose (It's also hard to find someone to install it. Anchor Insulation, located in Charlottesville, is the only company offering it right now), and that's not including drilling holes, removing wall sections and siding, and repairing them afterwards. But the energy saving rewards are considerable. Basically, when you retrofit your old home with Aircrete, your walls become as airtight as any new green home you're likely to find.   

Of course, before you commit to this, it's a good idea to do a little energy auditing of your own. Simply blocking drafts around doors, windows, and electrical outlets, something you can do yourself with caulking, tape, or wallboard, can make a big difference. One simple way to check for drafts is to wait for a particularly windy or breezy day and walk around your house with a stick of incense, holding it near windows, electrical outlets, doors, etc. How sharply the smoke drifts will tell you how bad the drafts are. 

You might also consider having a professional energy auditor test your home, as they can tell you the most cost effective way to improve your energy efficiency. You may find that the money you were thinking of spending on retrofitting your insulation could be better spent replacing an old furnace or single-pane windows.