On the Level: Retrofitting Insulation in Walls of an Old House
Q: I have a 1940 “Colonial” that looks like a raised Cape Cod. When replacing the single-pane slider to the deck with an Andersen® slider, we discovered that under our aluminum siding was cedar shake. And under the cedar shake was 1x12s and then plaster. There is no insulation. Then I heard that “Houses before World War II didn’t have it” line, and realized why the utilities were so high.
I have since taken all the old blown-in insulation out of the attic and replaced it with 6-8 inch pink fiberglass. And I built an attic box wrapped in insulation to cover the stair pull-down where most of the heat escapes.
I plan to re-side. Should I strip the siding and the cedar shake and put some sort of Tyvek® wrap on and then side back? Or should I just re-side over the cedar shake and have the goop blown down the walls? I am told that may run $5,000. Seems like a lot compared to Tyvek®. What are your thoughts?
A: Tyvek® is a house wrap and has the insulation qualities nearly equivalent to the paper this is printed upon. Its function is that of a barrier and not a blanket, so take that out of the insulation side of your equation. It’s true that most houses built prior and, to some degree, for a while after, World War II, didn’t have insulation. They were certainly making and selling insulation prior to the war.
The notion of using something in a wall or ceiling to keep a house warmer or cooler has been around for a very long time. I’ve seen pine needles, straw, mud—even corncobs—stuffed into wall cavities of old homes with the clear intent to make the inside cozier. You’re on the right track doing what you’ve done up in your attic. I probably would have left the old insulation in place and gone over it with the newer to thicken the net amount of insulation in place. Sometimes, old insulation products will have asbestos in them, so leaving insulation alone is considered a good idea.
Covering the drop stairs is also a very good idea, but most people won’t go to such extents. In over 30 years of inspecting houses, I’ll bet I’ve only seen maybe a half dozen or so drop stair covers. I normally suggest weather-stripping the opening at the very least. After all, it’s an uninsulated door to the exterior. The air in the attic is outside air that during some seasons, like summer, is more severe than the air outside the front door. Hot air will both convect and radiate heat through this opening into the house below, increasing the cooling load and consequently driving up cooling costs. You’ve rightly identified those drop stairs as a big wintertime heat leaker. As long as what you’ve done is tight, you’ll benefit year round.
If you are planning to re-side your house, then what I read between the lines of your letter is that you’ll be tearing off the old aluminum siding and re-siding with vinyl. Good plan. Now, you can use Tyvek®. It’ll help, but it won’t be the cure. Most siding installers place a fan-fold type, thin, foam insulation board behind the vinyl they install. Again, it’s a help, and you’ll feel the difference, but it’s still not the cure.
I did some checking on the costs and methods of insulating the insides of your exterior walls. The foam system, to which you refer as goop, would probably be the method I would choose. The hole needed to get it into the wall is small, and the product flows around minor obstructions and doesn’t settle over time like a loose material would. You’ll end up with 3-1/2, maybe 4, inches thick of material in the walls that will make you snug as a bug. The median job price I heard for such an installation was between $3,200 to $3,500. If you realize a savings of $400 per year in lower heating and cooling costs, then your payback period is just over eight years. That’s certainly worth considering.
While we’re spending your money, what do your windows look like? If they are 1940 originals, then you’d be wise to consider replacing them during the re-siding effort. They will cost more than insulating, but if they are leaky, you’ll be taking a big step in the right direction by replacing them.
ASHI Director Jim Rooney, Freestate Home Inspections, Anapolis, Md., writes a column for several suburban Washington, D.C.-area newspapers with a combined circulation of approximately 400,000. This column appeared in April 2004. Writing a column keeps Rooney’s name in front of readers who may someday be looking for a home inspector who knows how to tell them what they need to know in language they can understand.
To Read the Full Article
ASHI offers its members unparalleled resources to advance their careers. ASHI offers training for inspectors at all levels of knowledge and experience, including resources about all major home systems. Members benefit from a vast network of experienced professionals, providing a community for mentorship and knowledge sharing..
In this Issue
FIND A HOME
INSPECTOR
Professional Networking
Grow your professional network, find a mentor, network with the best, and best part of the community that’s making home inspection better every day.
