house wrap and rigid foam insulation

[fordtruckin]

Wife and I are adding an addition to our house this summer. Wasn't contemplating rigid foam until recently just to help with thermal bridging and getting an extra couple R's. Walls will be 2x6 at 24"oc. The 3 walls we are adding are not load bearing as it's enclosing a post/beam deck which is why I'm going 24oc to get as much insulation in there as possible. The roof is already snow load rated so just need to insulate. If I wrap the addition in 1" of rigid foam, would the house wrap go between the OSB and foam, or between the foam and siding? I've searched the interweb and found both ways described. I have minimal experience with foam insulation and always thought it was a WRB when used as a wall insulation. I feel like I'm over thinking this.

[Hunter65]

Ford
You're probably over thinking this. Most rigid foam is also an air barrier, so you can tuck tape the joints and call it good. Im not sure what WRB is that you refer to. However, do your own research on rigid foam as an air barrier. Meanwhile, check this out:

https://publications.gc.ca/site/arch...3-2013-eng.pdf

You might have to click English......

Canadian Wood Frame House Construction. Excellent book for free. Look up insulation, air barriers and vapor barriers. Also check out CMHC's website.......tons of very good info on all kinds of home stuff if you look around. Google CMHC.

There are other options to keep thermal bridging to a minimum while maximizing insulation. PM me if you want more info.
Mike

[Blastoff]

Use rigid, tape the joints and put in some bubble wrap first and tape the seams,
Or what did you do??? You maybe done already.

[Puddle]

It depends if you have air permeable rigid insulation or not.
Ener-Air is but Ener-foil is not
EnergyShield CGF is but EnergyShield is not.
Plain English, is if it’s foil backed, you can tape the seams and you don’t need house wrap. If air can pass through it, you need housewrap.
I would stay away from pink or blue insulation as they are an inferior product to the new polyiso insulations.

[pikeman06]

I stripped down my old house and put rigid a0nd then wrapped it years ago. What did I save? Not sure. Put a high efficiency furnace in the old shack at the same time. All the hot air goes out the exhaust so i can't give a reasonable opinion...the whole system is a total joke. Get your wallet out it's all expensive and look at your heating bill. It's all service costs anyways. Spend a bunch of money and save 3 dollars a month.

[crosman177]

Soprema v Alu insulation will be your best option.

https://soprema.bynder.com/m/2beb4ed...Insulation.pdf

https://soprema.bynder.com/m/2beb4ed...Insulation.pdf



Research it. You can special order at Convoy Supply.

Send me a message and I can supply pricing.

[wallz]

We use a 5/8" foam on all our new builds. Exterra product. It is foil based.

The reason for the foil, is it is the exterior house wrap. All joints get taped. No other wrap required. It is our vapour barrier.

The reason for 5/8", is because anything more than that and you need to add strapping for the exterior siding. The foam is rated for max 5/8" before the nails will sag. Having to add strapping just adds to the cost, and the overall thickness unnecessarily.

We have used 2" and more when the customer requests it, but it is way more work and planning. The windows/doors will need special attention then as well.

[lmtada]

Originally Posted by pikeman06

I stripped down my old house and put rigid a0nd then wrapped it years ago. What did I save? Not sure. Put a high efficiency furnace in the old shack at the same time. All the hot air goes out the exhaust so i can't give a reasonable opinion...the whole system is a total joke. Get your wallet out it's all expensive and look at your heating bill. It's all service costs anyways. Spend a bunch of money and save 3 dollars a month.

Correct. Same applies for Solar systems (we have a 3.5kw system), all the transmission, administration fees, neglect the little power we created. Farce. I’d go with off grid next time. Batteries are becoming better.

[fordtruckin]

Well I’m done framing and the electrical. Was getting down to the wire so bit the bullet and went with an R19 insulation in the walls as that’s all I could find that day and 1” rigid foam to wrap it all under the siding. Should be an r24 give or take without it doing all the math etc… Siding comes Thursday and I went with LP Smartside. Their instructions show you can put house wrap either under or over rigid insulation depending where you live. Talking with a couple contractors in town I decided I’m going with the house wrap under the foam. I know I’ll have to get furring strips to instal the siding but that will actually work out well given the way the floor was built. It’s only a 145 sqft addition next to the great room with a woodstove. Got a cadet heater rated for 175sqft so hopefully that will keep the room warm. Rest of the house has baseboard heat and I’m not generally a fan. I do miss a forced air furnace.

[Au revoir, Gopher]

I know it won't help you with your current project, but this stuff looks very interesting. Not sure how it would work with a reno, but could be something to consider with a new build. "2x4 Framing. R-12 Batt & 936 Connect Achieve Effective R-22. Includes Vapour, Thermal & Air Control Layers. No OSB Sheathing. No House-Wrap."

ARG

[Redneck 7]

Have you thought of going 2x6 plates and 2x4 studs staggered so there isn't any thermal bridging?

[calgarychef]

I’m only a chef not a contractor but I worry about excess moisture with all this non-permeable wrapping nowadays, especially if it’s simply added to a house and not planned for in the original building.

[Vingiu]

Originally Posted by calgarychef

I’m only a chef not a contractor but I worry about excess moisture with all this non-permeable wrapping nowadays, especially if it’s simply added to a house and not planned for in the original building.

100% correct. There are two ways around it - you can wrap a house up tight, with absolutely no moisture or air movement, or you can let it breathe as much as it needs. Either way works effectively, but as far as I’m concerned a structure needs to be built one way or the other

[fordtruckin]

Originally Posted by calgarychef

I’m only a chef not a contractor but I worry about excess moisture with all this non-permeable wrapping nowadays, especially if it’s simply added to a house and not planned for in the original building.

Rest of the house has a hybrid flash and batt system. Spray foam and Fiberglas batt. When we moved in there was moisture in the house and we ran a dehumidifier most all winter. We replaced the windows and last winter the dehumidifier did not pull much moisture so we didn’t use it a lot. The moisture was evident on all the windows before we replaced them as they froze up badly.

[QUOTE=Redneck 7;4646026]Have you thought of going 2x6 plates and 2x4 studs staggered so there isn't any thermal bridging?[/QUOTE

Framing has been done for a week or so it’s past that point.

[Gboe8]

I did two inch on my house. Osb then house wrap then foam then strapping and then siding. As stated above it adds a lot of extra work.

[MyAlberta]

From your poly vapor barrier, to the exterior, you want vapor transmission. Furr the rigid off the wrap, or use a drain mat between. The rigid and siding make up the rain screen.

[EZM]

Originally Posted by MyAlberta

From your poly vapor barrier, to the exterior, you want vapor transmission. Furr the rigid off the wrap, or use a drain mat between. The rigid and siding make up the rain screen.

Sorry, maybe I misunderstood you, but if you place firing strips (and an air pocket behind the rigid) then what's the point of the rigid insulation as it no longer is in contact with the structure allowing cold air behind it? Usually the rigid is in contact (or made with) the sheathing to provide insulation.

I'm not an expert, but just seems like a total waste of money and material if it is providing no contiguous insulation to the structure itself you are trying to insulate.

[fordtruckin]

Originally Posted by MyAlberta

From your poly vapor barrier, to the exterior, you want vapor transmission. Furr the rigid off the wrap, or use a drain mat between. The rigid and siding make up the rain screen.

That’s not how the rigid insulation company or the siding manufacturer recommend installation. House wrap, rigid then furring and finally siding. Any moisture will escape/dry between the rigid and siding with the furring gap.

[MyAlberta]

In Alberta, that space is where condensation takes place, with that construction. A rigid board up against the wrap will lock it in. A bug screen at the bottom, closed in at the top. Yes, the manufacturers will recommend a procedure that doesn’t unduly add cost, to keep their products moving. A drain mat is best, and it will add an R or two.