I'm hoping I've come to the right place for some expert advice!
We need to put a new roof on our old house, but it is turning out to be quite a education process in trying to figure out what the 'right' thing to do is in our situation. (I'm your average homeowner who is learning about roofing via the internet & by talking to a boat load of contractors!)
Here is the back story:
House is a 2 1/2 story cape. Built 1826. Has ell addition on back that dates to about same time. Current roof is 16 years old. Roof is leaking in valley area & shingles are coming off in wind storms or when roof raking during the winter.
Roof deck is original wide pine with large gaps. Rafters are spaced randomly...well, maybe average 24" apart. Rafters vary in thickness, but about 4" deep. Shingles are in reasonably good shape, but installation was sub par. (Previous owner installation of course!)
No ridge vents!
So we have 3 separate roof architectures (from low to high) knee wall, then 5' section of vaulted ceiling in our upstairs bedrooms, then an unheated attic space.
Our biggest problem? ICE DAMS at the eves..all around the house from heat loss.
There is currently some batten insulation in the knee walls, but it has gotten wet & broken down over the years. No insulation in the vaulted section - just the plaster, airspace & roof deck. The attic floor is tongue & groove board that we think has pink insulation underneath.
Here is a photo of the house so you can get an idea of what we are dealing withhttp://www.flickr.com/photos/59009466@N00/3864410245/
I've also been told that roofs need to be ventilated. We have no soffits, nor the ability to put them in the knee wall section due to the construction style. Our 3 sections are not joined for proper ventilation. No ridge vents either, only 2 gable windows & an attic fan.
I've been given conflicting advice on how to best handle a situation like this. A 'hot' roof vs. a ventilated roof.
1. Hot: Use closed cell spray foam on the backside of the original roof deck for 2/3 of the roof. (Knee wall & vaulted sections.) So we would have the following layers: 4"-5" closed cell, original roof deck, new plywood, felt & IWC, then new shingles & ridge vents. Attic portion could either have spray foam on roof backside, or 2nd layer of un-backed roll insulation on the attic floor for about the same r-value. (There is a 4K difference between those two choices!)
2. Ventilated: Elevate the roof deck from the outside, so you have now created an airspace from soffits to peak. So we would have the following layers: 4"-5"closed cell foam, original roof deck, 2 1/2" strap spacers, new plywood, hix vent, felt & IWC, then new shingles & ridge vents. Attic portion could either have spray foam on roof deck backside, or 2nd layer of un-backed roll insulation on the attic floor.
Now the price difference between options 1 & 2 is about 12K! (Not including the foam vs batten option for the attic!) That is a lot of $ to us when we also have a 63x36 antique barn to re-roof as well. Going with option #1 would pay for the barn re-roofing.
I've been advised by several people not to do the hot roof scenario on this old house. It is considered new technology, expensive, not easily reversible, water damage is harder to identify, shortens your shingle lifespan. But I've also heard it is great...it is a vapor barrier, about R7 per inch, does NOT shorten shingle life by any significant amount, adds to roof rigidity & would just about eliminate the chance for ice dams because it seals up every nook & cranny.
What do you all think? I'm all for option #2...better safe than sorry, but I'm wondering if it overkill? And it is double the cost. $ is a factor here, but I don't want to make decisions solely on cost. Has anyone had any similar experiences?
Thanks for taking the time to read this!