Should you insulate an A-frame cottage with cathedral ceiling from the exterior or interior?
We have a 20'x30' Aframe cottage that we have started a reno on. We have removed the panelling inside and the outside boards are visible and in great shape. Shingles were incorrectly installed though, so need replaced, and we were planning to put a steel roof on instead. The boards inside are exactly the look we are wanting inside. We were going to create an air space on the boards, put the panelling back on and insulate before adding our interior walls of new tongue and groove. However is there a way we could keep the interior as it is, and insulate on the outside? We then have to figure out a way to hide the wiring. It is located in Ontario where winters can vary between freezing and -20. Thank you!
To turn a 3 season cottage into a 4 season permanent home is always a bit tricky, in the case of an A frame that will be open on both sides it is obviously a bit easier because you have options. In order to do this properly you need to build for your specific climate, may I ask where are you located? That will help determine the best amount of insulation to install.
And to be sure I understand, it sounds like your preferred finish is to leave the rafters and bays between them open as the interior finish, which would mean insulating the outside. If that is the case, yes you can, you would want to insulate it the way you would exterior walls, and then install your metal roofing afterwards (great choice on metal btw), so have a read here first –
How to Insulate Exterior Walls from the Outside in the US & Canada
That page also has a building science basics video, watch that as it will help you understand the steps involved as well. Without knowing where you are I can’t speak to vapor barrier placement and how much insulation, but since you mention that it is boards, and not plywood or OSB, you will for sure have air leakage though them, so step one is an air barrier membrane. You can see our Air Barrier DIY install video here, and with knowing your climate zone we can go over options together.