Attic insulation repair & upgrade
An insulation repair and upgrade is in the works and I’m looking for input.
1000 sq foot 1956 bungalow with a hipped roof. The roof rafters are 2×4, the ceiling joists are 2X6 and the walls are 2×4. I’m in Calgary Alberta so winter temps can get pretty close to -40.
I currently have about 5 inches of wood shavings with R20 fibreglass batts on top, mostly running parallel to the ceiling joists. There is a wax paper vapour barrier on the ceiling.
The woodchips and fibreglass are packed tight to the roof decking.
There’s a “Government of Canada Improved Thermal Insulation Program, 1980†sticker on the furnace duct. There must have been credits available at the time.
I’ve pulled back some batts and raked back some wood chips from between a few of the rafters to see what’s there and to get some venting from the soffits. There’s probably less than two inches from the roof plywood to the edge of the top plate.
Here’s my thoughts:
Pull back all the insulation from the roof/wall junction and install baffles in each rafter bay.
Lay a block of rigid foam on the ceiling, overlapping the vapour barrier and top plate.
Seal the baffle/foam in place with some spray foam.
No baffles in the corners and probably just whatever foam I can get in there to create an air seal
Push the wood chips back
Trim the fibreglass to length and re-install.
Add vapour barrier at the light fixtures and around the sewer vent and block chimney (only has a liner pipe for the hot water tank in it now).
Fluff up and improve the fit of the original batts where necessary.
Add a layer of R20 or R28 batts perpendicular to the first layer. Same amount of labour and only $150 or 20% more for the R28.
Questions – Will acoustic tile sealant, tuck tape or spray foam stick to the wax paper vapour barrier?
I haven’t priced out cellulose, any big advantage over the new layer of batts?
Anything else I’m missing?
Thanks in advance,
Adam
Replies
down and dirty ???....
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i'd blow about 20 inches of cells right over the top...i wouldn't pull up any batts or move any shavings
i'd also do a blower test and smoke test to find any by-passes
At the very minimum, I need to get some air flowing into the attic space. otherwise the only ventilation is three square roof vents, near the ridge. I think installing baffles is a must.Adam
screw the ventilation... it does just about zero... keep the warm moist air OUT of the attic.... air seal at the ceiling lineMike Hussein Smith Rhode Island : Design / Build / Repair / Restore
Air seal is what I'm aiming for with pulling back the chips at the roof/wall junction and adding the foam. Also the vapor barrier around fixtures, vent stack etc. Any thoughts on getting a seal to the wax paper?
i'd start with the blower door /smoke test....that'll tell the story... then i'd over blow all the batts and wood chips... and forget about the stupid ventsMike Hussein Smith Rhode Island : Design / Build / Repair / Restore
I've had a blower door test done and the house leaks a lot. I need to do a lot of sealing on the outside. The exterior is stucco and parging on the foundation. Just about nothing is caulked. That's on the list too. Windows aren't great but will probably wait until next year.Looking at the brochure of the locally available loose cellulose(Weathershield), 8 inches would give me an additional R30. The material cost is less than batts but I don't know what the blower rental would be.Adam
Lowes and Home Depot (if you have those stores locally) will loan the blower for free with minimal purchase of cellulose bags. I seem to recall it is 20 bags here.
Quantum materiae materietur marmota monax si marmota monax materiam possit materiari?
We have home depot and they rent tools. I'll call in the morning and find out some prices.
Should be free, if you buy the cells from them.
Of course, the blowers they supply are nowhere near the size/effectiveness of the units the pros use.
As I stood before the gates I realized that I never want to be as certain about anything as were the people who built this place. --Rabbi Sheila Peltz, on her visit to Auschwitz
the blowers they supply are nowhere near the size/effectiveness of the units the pros use.
They'll do the job, loose cells in an attic just need enough blower to move the material.
It ain't rocket science.
Joe H
Yep, they will blow loose cells into an attic with no problem.For dense pack into a wall cavity, well, your mileage may vary depending upon the unit they have and how well it has been maintained/abused.If you REALLY had to, you *could* just dump out the bags into the attic and use a garden rake to break clumps and spread it around. Kinda messy, but doable.
Quantum materiae materietur marmota monax si marmota monax materiam possit materiari?