Insulating exterior walls with new insulation in a hidden wall cavity during an upgrade is challenging. Insulating outside walls cavities with injection foam shows promise as one solution.
It’s not unusual for a household to consume twice as much energy as necessary. Of course, there are many “culprits” responsible for this high energy demand: an inefficient water heater, phantom loads from electronic devices, leaky ductwork and an outdated furnace, just for starters. But one of the most common denominators in energy-wasting houses is inadequate insulation – or more specifically, too many air leaks and too little insulation.
In earlier blogs, I talked about the importance of air-sealing and insulating the attic according to recommendations established by the U.S. Dept. of Energy. If you have access to your attic space through a hatch or drop-down stair, your attic is a good candidate for an insulation upgrade with blow-in cellulose or fiberglass insulation. You can rent an insulation blower yourself or have an insulation contractor do the job, after sealing leaks between the attic and the living space below.
Beefing up the insulation in your walls is a different matter. In many older homes, walls are framed with 2×4 studs and either have just R-13 fiberglass batt insulation or no insulation at all. Even when there is insulation in exterior walls, there are certain to be air leaks that allow frigid winter air to come into your living space around electrical outlets, window framing and through other air leaks. Flawed installation details can also hurt energy performance. A small void or area where insulation is missing can cut a wall’s overall insulation value by as much as 40%.
Improving wall insulation can be challenging. After all, who wants to go to the expense of removing interior wallboard or exterior siding and sheathing in order to access a wall’s stud cavities? Another alternative – removing exterior siding and then covering walls with rigid foam insulation – is also expensive and disruptive. So what can be done to solve this energy and comfort problem?
Injection foam is proving to be an excellent product for upgrading existing wall insulation quickly, affordably and with minimal disruption. Standard two-part foam can’t be sprayed into wall cavities because its expansive force will pop wallboard and sheathing off studs. But injection foam is non-expanding. It’s designed to flow and fill around electrical wires, outlet boxes and existing underperforming insulation. It seals air leaks, fills voids, and provides very high R-value: up to R-5.1 per in. when temperatures are close to freezing.
To upgrade wall insulation with injection foam, workers drill small (typically 2-in.-dia.) holes in each stud bay, from inside or outside the house. The stud cavity is then filled with injection foam from a flexible hose, and the access holes are plugged.
Another thing I like about injection foam is that it’s not hazardous to handle. Workers wear safety goggles and gloves rather than respirators and hazmat suits, which are required when installing standard two-part spray foam. Injection foam overspray cleans up with water rather than solvent.
Recently I watched a crew from a Connecticut-based company called Dr. Energy Saver install injection foam in the walls of a ranch house. Workers removed a course of vinyl siding to access the wall sheathing. After drilling access holes, the injection foam was (there’s no better word) injected into each cavity. The foam looks like shaving cream and has a similar consistency. In just a couple of hours, the job was done. Small amounts of foam were evident inside the house, where the material filled gaps around electrical outlets. Cleanup was easy, and I came away with no doubts about the effectiveness of this technique for sealing leaks and upping wall insulation value.
