|
| Author |
Message |
Alpine_Junky
Member
|
# Posted: 21 Sep 2020 05:01pm
Reply
Looking for guidance on how to insulate a T&G pine flat ceiling; 2x4 bottom chord of trusses is what its getting nailed up to. Roof is a 7/12 pitch (30' wide) and has metal and plywood as outside coverings. 16" o/c trusses. Has an outside overhang I plan to use perf metal and insulation baffles for airflow on both sides of roof.
Wondering if batts are the way to go or if I could / should figure out some kind of air barrier and use blown in insulation? Would the blown in insulation at R49 value be too heavy on top of the pine T&G (I am using 15 gauge finish nails on each truss to attach.) Basically looking to get enough insulation up there without breaking the bank -- 1400 sq ft ceiling abouts, located in northwest Montana where the energy guide seems to suggest R49 - R60. Single source of heat will be wood (cheap heat!  . Thanks!!
|
|
Alpine_Junky
Member
|
# Posted: 21 Sep 2020 05:11pm
Reply
Would plastic sheeting for the blown in insulation to sit on be an effective enough barrier if blown in insulation is an option?
|
|
Brettny
Member
|
# Posted: 22 Sep 2020 06:57am
Reply
Plastic sheething then putting your pine ceiling in and blowing will be fine. Pine is alot stronger than the 1/2in drywall that's holding my blown in.
With a metal roof you should shoot for the r60. Any amount of heat loss or air leaks with a metal roof can be bad. Vents help too.
|
|
Nate R
Member
|
# Posted: 22 Sep 2020 08:03am
Reply
Whatever you do, make sure the ceiling has a good air barrier.
|
|
Alpine_Junky
Member
|
# Posted: 22 Sep 2020 10:36am
Reply
Nate R
Do you have any suggestions on what kind / brand of air barrier to use?
|
|
Alpine_Junky
Member
|
# Posted: 22 Sep 2020 10:48am
Reply
This was what I based my understanding of creating an air barrier on / part of the research I did before I asked the question: https://www.ecohome.net/guides/2298/what-is-an-air-barrier/
My thinking was to use the poly film and be as diligent as possible with sealing it up to the trusses with staples, etc. The wood over it and the insulation pressing on it from the top should, at least the way I understand it, provide both an air and vapor barrier.
Am I on the right track with this? The climate of NW Montana is very dry almost year round with few humid days, most precipitation is snow; however the cabin will be heated and I will have a pot of water on the stove with the intent to live in the cabin full time. I plan to watch the roof very closely to ensure there is plenty of ventilation and I don't get heat up there so the roof sheds vs icing and freezing. I have the ridge vent and each of the soffits will be vented. I am also thinking of putting in some vents in the gables.
|
|
mj1angier
Member
|
# Posted: 24 Sep 2020 06:55pm
Reply
This kind of sounds like what you are dealing with:
https://www.greenbuildingadvisor.com/question/add-rigid-foam-above-the-deck-on-re-roo f-tg-roof-deck-is-ceiling-no-attic-exposed-rafters
|
|
toyota_mdt_tech
Member
|
# Posted: 24 Sep 2020 07:36pm
Reply
Here is how the log home builders do it. Rafter in place, go up the rafters on top with your T&G, now frame in studs of 2X12 on top of your T&G, do your 16 or 24" OC, install your insulation, open it at the soffit and peak so it breathes with some vents, sheet over top of it, then felt and your roofing.
|
|
|
Alpine_Junky
Member
|
# Posted: 24 Sep 2020 07:55pm
Reply
Brettny
Can I buy you a beer? (Or send you a care package?) Your suggestion about moving the trusses to 16 o/c saved my bacon and would love to express my gratitude for your help.
|
|
Brettny
Member
|
# Posted: 25 Sep 2020 06:00am
Reply
Your welcome. No need to send anything. Just help someone else some day.
|
|
|
