Vaulted Ceiling Insulation Delema
Hello,
I have a Home in Northern Ontario (Zone 7 I think) that was built in 1963 and has a bunch of Vaulted Ceilings. As the house was built in the 60’s you can imaging the insulation standard were not super great. We are very prone to ice damming and keeping a comfortable temperature is pretty much impossible (especially in the bedrooms above the garage). Last winter we started getting water spots in the living room (right side of the house) along the wall and this winter some more have formed. This is very likely because of ice damming and likely means the roof is going to need to get done very soon.
As we are looking at a potential roofing job I wanted to try and re-insulate the ceilings from above. I had a few roofers come take a look and some wouldn’t even quote me because it is a 12-2 pitch so allegedly, they may not be able to warranty a normal shingle. The Rafters are 2×8 and right now I know that there is maybe 4 inches of paper back insulation in the rafter bays as there are 2 “normal” attic spaces where I can see parts of the vaulted ceiling rafters. I know that spray foam would be the 100% best option here but as always, I wanted to see if we have any more economical options to improve what is already there. I’m hoping to get some opinions and thought on how some “experts” may deal with this.
One of the biggest things stopping us from just going all out is that this is not our forever home and spending 50K on an insulation and roofing job just would not make sense as we would NEVER recoup that cost, not to mention we really can’t afford it. I have included some pictures and notes to try and best explain and show how the house is laid out. I am assuming that the rafters above the garage bedrooms are vented from the soffit to the 2 Attic Spaces. I am also assuming that the rafters running from the front to back of the house are vented from soffit to soffit.
Any advice is greatly appreciated.
I have Attached a PDF with pictures and descriptions
Thank Again!
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Replies
Rusty roof nails generally mean air leaks from inside. Since fixing this properly will never pay, I would focus on getting those air leaks sorted. Reducing the air leaks will also help with the icing issues.
If you really want to fix it, I would vote for another option. Build a new roof above the existing to get you to at least 3:12. This would fix the shingle issue and get you an attic with more space for insulation, you can now loose fill the whole attic. When doing this, I would pull back the existing insulation above the wall plates and spray foam those from top to seal it up.
Since it is a simple roof, the exterior rigid option would also work but you would have to dense pack the rafter spaces from above to get rid of the gap. With a 2x8 rafter, you will need a lot of rigid above the roof deck though and still won't fix the slope issue. More about hybrid rigid/fluffy roof here:
https://buildingscience.com/documents/building-science-insights-newsletters/bsi-100-hybrid-assemblies
The only areas that could be venting into the attic spaces are the bedrooms above the garage and the spaces underneath the attic spaces. I suppose I could try to seal the light fixture boxes and better seal the attic doors to try and solve the air leaking in that section. Other than that the ceilings are all thick plaster and there are no holes or cracks.
This does not help with the rest of the house as each rafter seems to be its own vented space (maybe not? It would be hard to tell without ripping the roof off). It’s this section (left of the house) that has the most ice damming and the water spots starting to form. In the winter we can actually see the rafters against the plaster because of the temperature difference. Ill attached a few pictures one I get to a computer.
I will explore the option of building a roof on top of the existing one. The
You may want to have an engineer run the number for your home and possible snow loads.
My gut says 2 in12 roof with 2x8 rafter and 36 + inches of snow will have a span of about 7 feet and the house looks wider than 14 feet.
OK you got sucker into a bad house. It is drafty, poorly insulated the shingles do not follow the manufactures instruction making it a code violation and I am not sure the roof can support the snow load.
The question is are you the kind of person that can sell it the way it is to someone else?
If you want to stop the ice dams you need to keep the warm air from leaking into the attic and melting the snow. That starts with a blower door testing and air sealing to keep the warm air out of the attic after that you can insulate. I think the attic needs to be properly ventilated or conditioned and I did not see any soffit vents and it is to flat for vents to work well at 2 in 12.
If you are keeping the 2 in 12 roof slope, consider a metal roof over 6 inches of sheet foam and conditioning the attic.
Yes, you will likely lose money when you sell but will not be passing a bad house off on the next guy.
Walta
The drawing is a bit misleading, there is a load bearing wall that runs down the middle of the house and the rafters meet there. I’m also assuming that is why that section of the house has them spaced at 12.5” on center. As for the question of morals it comes down to personal circumstances and capabilities. Am I the type of person to leave it this way? No I’m not and have been trying to figure out what to do with it for the last 10 years but again I have to stay within my means. All that to say that I may not have a choice but to sell it as is.
I appreciate the insight and ideas.
I have overlaid a low sloped roof with new scissors trusses (5/12 pitch) and left the old and fully insulated cathedral roof intact. A bit of an energy heel on the new trusses will get you up and over the existing roof. I provided eave and ridge venting for the new roof and blew cellulose over the existing roof deck.
You may have to use a peel and stick over the existing roof deck for a good air seal. I did not because I had a poly vapor barrier on the warm side of the original ceiling for air control.
This is not a job for roofers, but a skilled builder will have no problem. If you need good cold climate building advice look to builders with experience building in cold climates.
Doug
That's a difficult one, but I would rule out the cellulose option right away. An unvented dense-pack cellulose roof might work in a warmer climate with a very air-tight ceiling, but that's not your situation at all.
With spray foam, the R-value will be significantly reduced by thermal bridging through the closely-spaced rafters. Over 10% of the roof will still just be solid lumber.
I would lean towards the rigid insulation option. I don't know the OBC requirements, but the IRC would require a minimum of R-35 in zone 7 (assuming you don't add more insulation to the rafter bays). You could get that with about 6" of polyiso foam board. Even 4" would be a huge improvement over what you have now. Then add a second layer of sheathing and a low-slope shingle application (which is allowed down to a 2 in 12 pitch). And of course, insulate the exterior attic walls.
Before you get to the foam though, you'd have to block off the vents and insulate the ends of the rafter bays. Spray foam would be good for that, sealing off both the wall top plates and the vents. If you find any wet fiberglass, remove it, but the rest can stay.
You'd have to decide what to do about the overhangs. You could cut them off and build new overhangs at the foam layer. Another option would be to have the foam layer overhang the existing fascia boards by a few extra inches, giving a stepped fascia.
Ok so every rafter bay would have to be sealed off including the ones ending in the attic spaces? And then the attic space would also need to be insulated? Would that mean it would become a conditioned space? I suppose I would remove the insulation on the interior walls? I’m not quite following the problem with the over hangs… do you mean the ones on the front and back of the house since technically they don’t need to be there if they aren’t venting the roof?
Thank you for taking the time to reply!
You'd have to seal off all the rafter bays at the exterior walls only. Yes, insulate the attic walls -- you can reuse the insulation from the hallway walls. Cut some register grilles into the hallway wall to allow some air exchange with the rest of the house.
The overhangs look like they are about 10" thick already, so adding 6" to the roof will make them 16" thick. That will probably look excessively clunky, but that is of course a matter of personal taste.
Oh, OK. Yes, I understand what you mean now. And to confirm, I would not have to worry about the existing airspace between the insulation and the current roof deck once everything is sealed?