Retro-insulating sloped roof from attic

8 years ago

We are reinsulating the attic of our 100 year old home but are dealing with a difficulty. The top floor has a sloped roof about five feet high to the ceiling. When we bought the house, the previous owner had stuffed this from roof area with batt, which had blocked the soffits and caused premature aging of the roof. We unblocked the soffits, reroofed and added a ridge vent. We are now in the process of replacing the wood shavings and need to be able to insulate this area. We were planning to do spray foam but have been told they would need to rip out the dry wall of all the sloped areas (four bedrooms, three closets and a bathroom!) in order to do it properly. The problem with this (aside from the obvious increased work and cost) is that the drywall is over plaster which has been a misery to deal with in other parts of our renovation. We need a solution we can install from the attic area that includes a vapor barrier and the best degree of insulation we can achieve. Any advice is appreciated!

Featured Answer

PRO

K.O.H. Construction Corporation

8 years ago

Yes you need the baffles in both situations. I would think in your case blow-in would be easier going down the rafters. the sidewalls should be batts. The board from HD is fine.

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Comments (7)

Heather M
Original Author
8 years ago
An added question if anyone knows... we are hoping to add solar panels on the south slope of our roof at some point. Just wondering if there are any considerations we could make now.
PRO
K.O.H. Construction Corporation
8 years ago
are you saying the insulation remains in the rafters with no air baffles?
Heather M thanked K.O.H. Construction Corporation
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Heather M
Original Author
8 years ago
That's a question too. If we have the ridge vent should we be maintaining the access to the soffits with baffles also? In that case we're wondering if we can blow in insulation around them but we're still not sure about what to do about vapor barrier.
PRO
K.O.H. Construction Corporation
8 years ago
There is no easy solution. There needs to be air baffles for air circulation, if not you will have intense heat and moisture. If you have access and can install them along with blow-in insulation then it will be fine. In regards to Vapor Barrier, many paint companies make a VP paint and it works. Old houses have a lot of air leaks therefore moisture is not a big issue. I remodeled at least 50 100 year old homes and there was never a problem with moisture, leaks yes. If you can get to the side wall install the batts with the paper side in and install a wind barrier on the outside part of these wall such as fan fold or insulation board. This does work well.
Heather M
Original Author
8 years ago
Just so I'm clear, we need to do baffles whether we do batt or blow-in, correct? Is there any preference between blow in and batt? I looked up insulation board and found this. It says it is low profile and also a waterproof barrier. Would this possibly be a good solution? https://www.homedepot.ca/en/home/p.1001066322.html?eid=PS_GOOGLE_HD+%7C+PLAs_Shopping+%7C+Floors_Floors_pla-402951731677&gclid=EAIaIQobChMIuOXrxu331gIVVp7ACh11owXhEAQYAiABEgKHFfD_BwE

We will do the paint, thank you for that suggestion.
PRO
Ryan Olivieri, Inc.
8 years ago
last modified: 8 years ago
You can't access the bays from the attic by the ends of the collar ties? It would seem that one could slide sheet foam down the bays and push it down tight to the drywall. With old houses, sometimes I cut sheet foam about 3/8" too small and spray a tiny bit of foam around the edges. I'm guessing you have a perlin or something like a plate in the way.