A-Frame Insulation Retrofit
AFrameNewbie
| Posted in Energy Efficiency and Durability on
We purchased a 1980’s built A Frame home and put a new roof on the house. Some boards were rotten underneath and those were replaced, but there are cold spots around this area on the inside of the home. We had a spray insulation contractor come out and say they could not do much for us as there’s no outside access to the roof cavity without pulling off brand new shingles. The ceilings are tongue and groove redwood, and we would like to leave those untouched. Would it make sense to go through the knee wall which is dry walled and perhaps the basement ceiling?
Is there any way to add/repair insulation to our house in the ceiling cavity?
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Replies
You sloped ceiling needs to be treated like the cathedral ceiling it is.
So long as you are unwilling to disturb the both the interior and the exterior is seem the only options left a magical.
You may find this article interesting.
https://www.greenbuildingadvisor.com/article/five-cathedral-ceilings-that-work
Walta
AFrameNewbie,
Unlike walls, roofs with permeable insulation need to be vented. So the typical method of blowing cellulose in through where you can get access won't work. The roof has done alright because it wasn't insulated, and the interior warmth helped it dry. Pump in permeable insulation (especially in an older poorly air-sealed building) and the roof sheathing and outside of the rafters get colder. That's when moisture problems start.
The best way to retrofit insulation on existing A Frames (which like yours typically have nice finished interiors) is to add rigid foam boards to the exterior. As you have just re-roofed, that probably isn't a very palatable option.
All this is a long winded way of saying that without access to either the inside or out, you are unfortunately best leaving things alone.
"We purchased a 1980’s built A Frame home and put a new roof on the house. Some boards were rotten underneath and those were replaced."
Sounds like there already is a condensation issue.
Read the article that Walta posted.
A skilled carpenter may be able to remove and reinstall the ceiling planking without any obvious damage. It was probably installed from the bottom up, so it would be easiest to remove from the top down. You might be able to convert it to a vented assembly -- remove enough that you can slide in vent channels taped together, and then blow in insulation below them. You'd need to install a ridge vent and a soffit vent for that to work.
What does the roof do at the bottom? Does it go all the way to the ground? Does the knee wall come up and become an exterior wall? Is there a spot where you can create a soffit vent?
The bigger issue with A frames tend to be the lack of warm side air barrier. Typically the T&G is nailed on with nothing behind it. There is no easy fix for this, you have to demo the inside and install venting, insulation and air barrier or demo the outside and install exterior rigid.
Neither option is simple or cheap, so this could be a case of letting it be as is until major work is needed.