# Insulating Cabin ceiling



## 13moe (Feb 16, 2018)

Hey there,

I have a 12x12 cabin. The ceiling has 2x4's for raftors. I am planning on insulating the ceiling, putting vapour barrier up and then tongue and groove to finish. Is it worth me putting in R12 batts to keep it a little warmer for the Canadian winter?
OR, should I add 2x2's to the 2x4's so it would be closer to a 2x6...then I can use an R20 batt.

So basically, is R20 gonna be worth the extra work and $ for the warmth.

Thanks all


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## CodeMatters (Aug 16, 2017)

Guess it depends on how much time you spend there and type of heat source. 
If there's anywhere nearby where you can rent a blower I'd recommend blowing
in cellulose fiber. It's fast, easy and cheaper than other insulations. One of the 
local Home Hardwares lends out there blower for free when you buy the insulation
from them.


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## Nealtw (Jun 22, 2017)

Are we talking rafters or ceiling joists. Gable roof or shed roof? and what about venting?


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## chandler48 (Jun 5, 2017)

I think the OP is planning on insulating the rafters, which, without proper venting and air passage won't be very insulative (if that is a word). Air must flow from soffit vents all the way to a ridge vent in order for you to maintain good heat and cool in the cabin. With only 2x4's you won't be able to achieve any good R value due to the space taken up by the baffles for air movement.

Maybe you could post pictures of the inside of the cabin so we could see what you see.


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## 13moe (Feb 16, 2018)

Nealtw said:


> Are we talking rafters or ceiling joists. Gable roof or shed roof? and what about venting?


Raftors. The collar ties are high up to make it seem more open, so blown in won't work. It's a gable roof. (I've attached a photo). haven't really thought about venting to be honest. The wood stove helped obviously, but figured some insulation would help. I will only be up there a few times in the winter...It's more for the summer

P.S. No making fun of my build quality, lol. I built this in the middle of nowhere with limited materials...just to say I did it.


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## Nealtw (Jun 22, 2017)

I would add to the depth of the 2x4 by adding at lest another 2x4 or 2x6, air chutes from soffit to collar ties. And a ridge vent.
Even in the cool summer days you would like to keep it warm over night.


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## 13moe (Feb 16, 2018)

Nealtw said:


> I would add to the depth of the 2x4 by adding at lest another 2x4 or 2x6, air chutes from soffit to collar ties. And a ridge vent.
> Even in the cool summer days you would like to keep it warm over night.


There is a ridge vent now. And ya, I may add to the 2x4's and also add the chutes. thx.

Again. Just wasnt sure if the R12 would make any difference at all. Sounds like a no.


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## CodeMatters (Aug 16, 2017)

Every house I've ever lived in had R12 for at least a couple decades before 
being upgraded. Think R40 became code/norm about 30 years ago. For a 
place I was only spending 10 days/nights per winter (or less) I wouldn't 
spend any time/money on more than R12. 
With wood heat it's even more reason not to worry about it. You'll be wearing 
shorts in that little cabin when the wood stove is going.


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## Nealtw (Jun 22, 2017)

13moe said:


> There is a ridge vent now. And ya, I may add to the 2x4's and also add the chutes. thx.
> 
> Again. Just wasnt sure if the R12 would make any difference at all. Sounds like a no.


We always think about keeping heat in but with the roof you want to keep the everything the temp of the outside.
If you are using VB on the walls, allow them to breath to the outside.
We leave gaps between horizontal sheets and drill holes in bays below windows, That is why house wrap is made to breath.


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## Marson (Jan 26, 2018)

I would skip the ventilation personally. Venting isn't going to help the insulating value; it just provides a way for humidity to vent out of the building instead of condensing on the underside of the sheathing. It also can keep shingles cooler, but that is a non factor here. I would pack those rafter cavities full and and install a good 6 mil poly vapor/air barrier. 

If you only use this cabin a few times in the winter, the amount of indoor humidity is really going to be negligible, and thus the chance of condensation in the roof cavity.. With only 2x4's in the lid, you might melt some snow off of the steel roof when you get your wood stove cranking, but that is no big deal.

I built a cabin for myself, and while I have more insulation than you are planning (9" of dense pack cellulose), there is no ventilation whatsoever. Have not seen a problem yet.


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## chandler48 (Jun 5, 2017)

I know it is a remote location, but the only alternative that I can think of that would preclude the need for ventilation is spray foam, then your bead planks. Expen$ive, certainly. Effective, you bet.

But as Marson stated, the cabin is so small and the heater will probably run you to skivvies rather quickly, any insulation would be good.


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## 13moe (Feb 16, 2018)

I'm now thinking of buying a spray foam kit from the local hardware store. For $350, this kit will cover approx 200 sq feet at 1" thick.... Curious as to what the 1" would give me as far as R value. It doesnt mention it in the description.


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## Nealtw (Jun 22, 2017)

From a google search.

COST: Varies widely, but filling a 2×4 cavity to 

*R*-13 with closedcell ​

*spray foam*costs about $1.75 to $3 per sq. ft. Closed-cell ​

*spray*foams provide a higher​

*R*-​

*value*per inch than less expensive insulation types like fiberglass, cellulose, or open-cell ​

*foam*, all of which have ​

*R*-​

*values*of ​

*R*-3.2 to ​

*R*-3.8 per inch
Neat how they compare a 2x4 cavity to 1 inch of other insulations.​


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## 13moe (Feb 16, 2018)

13moe said:


> I'm now thinking of buying a spray foam kit from the local hardware store. For $350, this kit will cover approx 200 sq feet at 1" thick.... Curious as to what the 1" would give me as far as R value. It doesnt mention it in the description.


Update  even the DIY method would cost me just under $1000 for around a 5R value. I callled a spray foam company and they quoted me $2300....thats almost more than the cost of the cabin. With mice issues, i think I may just use rigid foam boards. Not the greatest R value but better than nothing. Thanks all for your input


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## 13moe (Feb 16, 2018)

One last question (hopefully)
With a limited budget, what would be the first part to insulate, the ceiling or the walls? Again, I plan on using rigid foam and then tongue and groove to finish.
Obviously heat rises, but if the heat is escaping through the walls before it gets to the ceiling......... Would walls be best to start with?


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## 13moe (Feb 16, 2018)

Marson said:


> I would skip the ventilation personally. Venting isn't going to help the insulating value; it just provides a way for humidity to vent out of the building instead of condensing on the underside of the sheathing. It also can keep shingles cooler, but that is a non factor here. I would pack those rafter cavities full and and install a good 6 mil poly vapor/air barrier.
> 
> If you only use this cabin a few times in the winter, the amount of indoor humidity is really going to be negligible, and thus the chance of condensation in the roof cavity.. With only 2x4's in the lid, you might melt some snow off of the steel roof when you get your wood stove cranking, but that is no big deal.
> 
> I built a cabin for myself, and while I have more insulation than you are planning (9" of dense pack cellulose), there is no ventilation whatsoever. Have not seen a problem yet.


Any batt insulation that is better than others with regards to deterring mice?


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## Marson (Jan 26, 2018)

13moe said:


> Any batt insulation that is better than others with regards to deterring mice?


Sorry, I don't know the answer to that one. Maybe roxul or something would be better? Do you have red squirrels? They will strip the fiberglass clean out of your walls/roof. Might be a good reason to go with rigid foam. 

Probably too late for this advice, but when I built my cabin I was very anal retentive about not allowing any gaps in the sheathing, including very tight bird blocking between the rafters.


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