I’m renovating an older house in a cold climate (montana) and am trying to figure out the best / most economical way to insulate the upstairs ceiling space. The rooms have 4 foot “knee walls” which then intersect the ceiling/roof. I’ve got native 2×4 rafters, and not enough headroom to scab on extra framing to allow for more insulation space.
I know the best way to go would be to hire an insulation contractor to spray in foam, but the budget will not allow for this. What is my next best option?
My current thinking is to buy 3″ rigid foam panels and tightly fit them between the rafters, leaving a 3/4″ space between the top foam and underside of roof sheathing for venting. I’d like to use foil faced foam if I can find it for a little extra reflective help.
Does this approach make sense? Do I need the ventilation space? Is it worth paying extra for the foil facing? Is there another approach altogether that will give me a better R-value? Is there a certain type of rigid foam I should use?
Thanks for your help!
Jon
Replies
Any chance of tearing off the shingles, putting rigid foam on TOP, then sheet and re-roof?
Would certainly seal a whole lot better, and could allow for 6 or 8".
Could do one side at a time - is the roof big?
A.lways a balance between time and money on personal projects!
Forrest
Thanks for your thoughts McDesign. I had thought of that, but the house has a new roof (less than 5 years) so I'd rather leave that alone. This one is going to have to be done from the inside. Any other thoughts?
Any chance of using Insulmesh and blowing in cellulose or chopped 'glas? Search "Mooney wall" here.
You'll run into a variety of opinions on roof venting - spend some time talking with someone familiar with your climate.
Forrest - in Atlanta
With only 3" of foam in Montana you better have a vent space because you'll lose enough heat to melt whatever snow is on the roof and cause ice dams. Can you at least run 2" of additional foam under the rafters? 5" of foil faced would give you around R35 which probably isn't enough but it's getting close.