Question: I live in a River Heights bungalow built in 1952 with three stucco exterior walls, and the front has vinyl over wood. The interior walls are plaster. I am considering insulating the exterior walls.
I am not enthusiastic about removing the stucco for this job, as it is in quite good shape. The basement is partially insulated with fibre batts in one area and rigid foam in other areas.
I have heard about closed foam insulation but I am not clear if drilling holes into the exterior stucco is effective.
A popular TV show handyman recommended the benefits of the closed-cell foam method, but he also suggested tearing out all the plaster walls to the studs and applying the foam. This is far more work and cost than I would want, seeing as there is nothing wrong with my plaster.
Is this a good idea or should I concentrate on re-insulating the basement? Can you comment on this or lead me into a better direction? Thanks.
— Al C.
Answer: While insulating the exterior walls of an older home should not be the first priority for energy efficiency retrofits, doing it from the exterior is often a viable option. There are two main choices and choosing which one to go with will depend on your budget and availability of good contractors in your area.
Improving the energy efficiency and comfort of a ’50s-era home often begins in two main areas, the attic and basement. It appears you have partially completed the basement upgrades, and I can safely assume that there has been additional insulation installed in your attic over time. Either way those two areas, especially the attic, should be initially checked and have upgrades to insulation, and particularly air sealing, done as needed. Air sealing is critical to prevent warm air intrusion and minimize condensation in both those areas. Using enough good-quality insulation and proper ventilation should be sufficient in the attic, while the basement walls may require installation of or upgrades to the polyethylene air/vapour barrier, as well as the thermal insulation.
After those two easiest areas are addressed, the next step should be one component of the exterior walls. While it may seem that the poorly insulated walls are a major contributor to lousy thermal performance, older windows are much more of a concern. In my opinion, no homeowner should think about adding insulation to the wall cavities before upgrading their windows.
Replacing windows with modern ones will not only lower heating costs, but will also make all the rooms in the home more comfortable. Not only do the older wooden sliders let the warm air escape the living space, they may also let a large amount of cold air leak into the home.
Now, once you have stopped heat and warm air from pouring out your basement walls, attic and windows, the final area to consider is the walls. Since they likely have wood or plaster lath, covered by plaster and multiple coats of paint on the inside, air leakage may be minimal through the middle of the wall areas. Most of the problem is at the corners, junctions between floors, and protrusions. Gaps between the framing in the walls and ceilings, inside corners, and electrical boxes may be the primary areas of concern. While the receptacle and light switch boxes could be sealed with spray-in-foam from a can, or a gasket weatherstrip behind the plates, the corners are more difficult to deal with.
The two main types of blown-in, retrofit insulation for exterior walls are plastic foam or cellulose fibre. Making the often-confusing choice between these will depend on several factors. Overall cost, ease of access for application and experienced insulation contractors may be the overriding variables affecting your decision. How easily a contractor can get good access to all the exterior areas of the home for drilling holes, dragging hoses and general work may help with this decision. If foam is your choice, higher-density polyurethane will be preferable to less-costly, lower-density products, due to the better air permeability ratings. As with any renovation job, asking the contractors about years of service with the particular product, references from previous customers and any workmanship warranties is critical.
Removing wall coverings and baseboards from interior walls, just to add insulation, does not make sense when better-quality insulation can be installed from the exterior, with only minimal damage to the finish. Choosing the right material and contractor for your home and bank account should ensure a more comfortable and energy-efficient home is the ultimate result.
Ari Marantz is the owner of Trained Eye Home Inspection Ltd. and the past president of the Canadian Association of Home & Property Inspectors — Manitoba (cahpi.mb.ca). Questions can be emailed to the address below. Ari can be reached at 204-291-5358 or check out his website at trainedeye.ca.