DIY spray foam and hot roofs

Lots of threads on here lately about insulation, so I thought I'd chime in with mine.

I'm thinking of insulating the cabin (attic ceiling and beneath the first floor - there is no crawlspace or basement, just open space under the house - it sits on log skids). There is currently some sort of 1950s rockwool (gyproc brand I think) in at least some of the walls, but no other insulation anywhere.

I think I'll do between the floor joists with Roxul (to prevent mice issues in fibreglass), but I am puzzled over the attic. There is living space up there, so I would like to insulate between the rafters in the attic ceiling. There are no soffits or ridge vents, and each end is hipped, so I think I need to insulate it as a 'hot roof'. In order to do this and deal with moisture issues, I think I need at least R20 of spray foam or rigid foam boards because we're in zone 5. We're on an island so getting a spray foam contractor out will be $$$, but cutting 4 or 5 inches worth of 2' wide rigid foam boards to fit between 24"OC rafters sounds like a nightmare. Has anyone ever tried a DIY spray foam kit like here: http://tigerfoam.ca/? Seems kind of dodgy to me.

Any other ideas? I would be grateful for any help.

Pic for an idea of the layout:

Thanks semipro. I guess I should get a few quotes before making decisions.

Hi all,

Sorry didn't realize this had been moved to the DIY board. Thanks for all of the replies!

Yes, I had considered foam board on top of the roof sheathing, but I was out-voted before we redid the roof (we put on cedar shakes that hubby hand-split himself - with a bit of help from our roofer friend).

If I do insulate, will I be able to tell when/if the roof starts leaking? We plan to maintain the roof well, but shakes don't last forever. We did put on zinc strips, so hopefully that will stop the moss from getting to it too quickly.

mike van said:

You burn wood at that house and put a cedar shake roof on it?

Click to expand...

Yep. It is the traditional material and believe it or not was the cheapest option for roofing. There were some decent cedar shake logs on the family property that the old-timers hadn't bothered with so hubby hand-split them all with a froe and mallet. Total price = sweat equity.

I'm not too worried, but we won't light up the stove if it's really dry. Considering it's generally damp here for 8 months of the year, that shouldn't be a big issue.

The Super 27 was great! We only use it on the weekends and our wood is/was sub-par so I'm looking forward to having better wood next year. I'm glad we went with a mid-size stove, even though the cabin is only about 900 sq ft it still takes a few hours to get everything heated up in the dead of winter. I was slightly worried about it being too big but it's not at all. I might even cave and put the electric blanket on the bed next year, but we'll see how much quicker we can get the stove up to temp with better wood. The stove size can be a bit much at this time of year, but small fires in the morning and the evening generally are working really well. We're still getting down into the mid-40s F (~7 C) here at night, so with almost no insulation it is still chilly in the cabin at night. We had our first afternoon over 70F today, so the time where we don't have to light the stove is coming .