inside insulation

[liteman]

would it be unwise to put eps foam board under drywall and over batt insulation on the inside walls along with sheathing and foam board on the outside? would i still need vapor/air barrier and where?

[glenn kangiser]

I'm not sure if there would be additional benefit.

Search "Super Insulated Wall" for more info from John.  http://www.countryplans.com/search.html

Here's some info from one of his recommendations from previous postings.

http://www.countryplans.com/cgi-bin/yabb2/YaBB.pl?num=1165944028

[rwalter]

I am in a similar situation in that this summer insulating my cabin/house is one of the projects that I have scheduled. Right now There are so many ways to insulate I not sure which way I want to go to. I have 2x6 walls. I'd like to super insulate as much as possible. I also have a cathedral ceiling that is built with 2x10's.

1.) Blown cellulose. Do you use wet spry? If so any problems with mold using this technique? I've heard as long as you allow it to dry long enough you shouldn't have problems. If you use dry cellulose do you use netting to hold it in place or do you install the drywall first. Either cellulose way you get a more air tight building than fiberglass but not as tight as foam. Cost is probably the cheapest or close to fiberglass.  

2.) Polyisocynate foam insulation blown in wall and cathedral ceilings however do you spray the cavity full or how much is actually needed I am not sure. Foam runs around 3.6-3.8 R per inch but it allows virtually zero air passage. Since the first 2-3 inches probably block 90% or more of the heat loss is this enough? The down side is cost and I am looking at having to have it installed professionally. I also received conflicting information regarding my cathedral ceiling. One contractor said blow the foam in the entire cavity with no air vents (baffles). Another said use the baffles and you only need around 5-6 inches. Again another said no baffles and just 5-6 inches..

3.)Fiberglass R19 in walls, R38 in Ceilings. One of the cheapest methods and I can install all of it myself. However it is not as nearly as airtight as either of the two above choices. Then again that may not be all bad since home built to tight might cause mold problems.

What are peoples perferences for insulation? My cabin is in the cold weather climate of upstate NY.

[Amanda_931]

I understand that the blown-in insulations completely fill the cavities.  Probably true of both the foams and the dense-pack cellulose.  There's no air to carry water vapor anywhere--in or out.

There are certainly people who think that the dense-pack cellulose is the nearly ideal form of insulation--often largely recycled content.  And others for whom Icynene is the best--and greenest--form of insulation.

I have a (probably) unreasonable prejudice against Icynene, but would consider Bio-based, which is supposed to use water as the blowing agent.

And my tolerance for little glass prickles on my skin is close to zero.  I know plenty of people who don't mind it nearly as much.  "All you have to do is wear long sleeves."  "And some sort of face and lung protection, and throw the clothes you were wearing out afterwards," I growl inwardly, when somebody tells me that.  Mind you, I have used fiberglass pipe insulation without going to all that trouble.  

Also why would you want to put something not quite solid under drywall?  Sounds like a recipe for having to replace the whole thing a few years down the line.

[John Raabe]

Solid insulation in the rafters is a hot topic right now. There is mounting information that the venting of cathedral ceilings can, in some cases, increase moisture problems.

If you go to some type of airtight spay insulation (foam or cellulouse) I would fill the cathedral rafters and not vent them (if allowed by your inspector). As for the walls, I would suggest a redundant two insulation system such as cavity insulation (of whatever type you want) and an exterior or interior foam board sheathing (1 to 1.5"). The foam sheathing insulates the framing and void cavities and adds about 1 1/2 times the R-value of the foam to the overall wall performance. This is cost-effective super insulation for your climate.

[skiwest]

Solid insulation in the rafters is a hot topic right now. There is mounting information that the venting of cathedral ceilings can, in some cases, increase moisture problems.

If you go to some type of airtight spay insulation (foam or cellulouse) I would fill the cathedral rafters and not vent them (if allowed by your inspector). As for the walls, I would suggest a redundant two insulation system such as cavity insulation (of whatever type you want) and an exterior or interior foam board sheathing (1 to 1.5"). The foam sheathing insulates the framing and void cavities and adds about 1 1/2 times the R-value of the foam to the overall wall performance. This is cost-effective super insulation for your climate.

I'm planning on going this route.  Will have exposed raffer beams with structural roof deck above that.

Options are foam and extruded board.  I'm out in the country and the town near by probably doesn't have a spray foam company.  Have looked into Tiger foam which is DIY.  works out to x2 for same R value as blue or pink board.

I'm thinking that if I cut carefully and foam any gaps, glue together etc  make one solid mass as much as possible  will be as good as foam.  Also will be able to screw roof decking directly down on top of insulation.  Will foam that won't work as would never be a level surface.

[John Raabe]

If you want to have exposed beam and decking on the underside of the roof structure, then you have to do all the insulation on the topside of the 2x6 (or whatever) decking. You can search for "nail base foam insulation panels" that combine several inches of foam with an OSB (usually) top layer that you can nail the roofing to.

[Amanda_931]

John Raabe wrote:

..."nail base foam insulation panels" that combine several inches of foam with an OSB (usually) top layer that you can nail the roofing to.

Oh, so that's how it's done.  

Hmmm

But how does that fasten to the roof decking so the whole mess doesn't come flying off

[tc-vt]

Strength is the other benefit to sprayed in closed cell foam insulation.  You wouldn't get this benefit if you used blue or pink board.  I recently came across something that said sprayed in closed cell foam made a wall panel able to withstand three times as much lateral force without shearing as a panel without the foam.

I bit the bullet and had my one and a half story 20x30 done with closed cell - about 4 to  4-1/2 inches in the roof and 2-1/2 inches in the walls with no venting.  It cost $5200.  

I only heat the place when I am home, so I come home in the evening to a house that might be as low as 48 degrees in the winter here in northern VT.  I used about one cord of wood and 100 gals of propane each of the last two winters.  This is without any interior walls yet, just bare studs.  It's hard to say whether this is a testament to the foam, the small structure or to heating a place only when you're home but maybe it gives someone some numbers from which they can extrapolate something useful.

An idea I had to thermally decouple the studs was to use strips of either 1/4 foam or sill sealer on the stud faces before applying the interior wall.  This inexpensive step may not amount to much in energy savings but it might be enough to keep the studs from telegraphing through to the outside walls as lines in the frost on the exterior walls (which I have seen several times).

Tom

[John Raabe]

But how does that fasten to the roof decking so the whole mess doesn't come flying off

Long screws that go from the nailbase down into the decking. The panel supplier will spec the fasteners. I've done up to 5" foam panels to meet code levels of insulation. This is, of course, more expensive than batt insulation.

Tom: Your foam job sounds like a good investment for your climate. Yes, a thermal break at the framing would likely be the next most cost-effective thing to do. There is a good article in the 09/06 Fine Homebuilding explaining how to install exterior foam sheathing under siding. Foam on either side would serve the same purpose. A 1" foam would double the R-value of the framing.

[glenn kangiser]

Bat's are more inexpensive to insulate as they use their own trapped air for insulation. :-?



Thermographic image of a bat using trapped air as insulation.

http://en.wikipedia.org/wiki/Bat

[John_C]

Bat guano could be used to create methane which would power a generator in off grid applications. Glenn, I think your onto something here.  Keep us posted on how it works out.  

[glenn-k]

That is an interesting concept- the methane could also be used in a heater the make the insulated bats be self heating.  It seems this may constitute perpetual motion though and that is supposed to be impossible.


I am not fully responsible for this concept.  John is the one who brought up the inexpensive insulating bats.


When I first read his comment, I thought of bat girl -- she could also generate warmth.


...but I didn't want to trash John's thread.


So I didn't post my picture of Batgirl.


Now I miss her... :'(


Why am I punishing myself like this :-?

[builderboy]

And they say bats are a great solution for mosquitos. I guess they'd just pass out on the sight of batgirl!  

[Okie_Bob]

Those of you that know me will not be surprised that I am a huge Icynene fan!!!! For all the reasons mentioned above. Yes, it is expensive but, I believe that for the long haul, nothing else is going to perform
as well.
I am buying into the 'no vent' side of this argument. More as a result of my roof design maybe than anything else. Had the option in my garage/apartment prior to installation but, already had a gable fan and soffett vents before I was exposed to 'no vent'. Wish I had known, would have gone that way.
Suspect you can find an installer within range of your project. Mine comes from about 50 miles away, no problem. You might have to pay them road time but, that wouldn't be too much compared to the installation cost you'll be looking at.
Think I'll talk to Icynene about paying me for all my free publicity I give them! What do you think Glenn? Would BatGirl help me?
Okie Bob

[glenn-k]

From what I know of her and you, BoB, you two would make a dynamite combination.  Icynene wouldn't be able keep up with the sales and installation.  Perhaps you would also be able to reveal her true identity to us -- if we asked real nice :-?

I have to quit now.  I have to go to the batroom. :-/

[fourx]

I have the wall which faces West lined with bats ( the non-batgirl fibreglass type) and the rest of the walls lined with one inch thich wool carpet covered with wood sheeting -I bought a housefull used for forty bucks. Works great as insulation but mice can be a problem if you don't have a cat.

[glenn-k]

Sounds cool Pete.  Lots of sheep down there so wool could be a bargain sometimes.  How does it compare to the fiberglass for quality of insulation or an R valueif you know it.

I wonder if a lifesize picture of Batgirl would keep the mice away :-?

[fourx]

I don't mind her little friends flying through the house on summer nights ( we have no inscect screens)  eating the mosquitos and pooping the processed results on my computer screen, Glenn,, but the thought of Batgirl doing the same thing is a little overwhelming, mice or no mice.
There is a form of wool based insulation available now which has a higher R rating tham fibreglass, it wasn't on the market when I was building. My impression is that the carpet is just as effective, bearing in mind that the winter night temperature is not cold enough here to produce any more than maybe one or two very light frosts each year.

[glenn-k]

Your climate has to be much the same as ours except opposite.

the thought of Batgirl doing the same thing is a little overwhelming

Pete, I don't think she's that kind of girl --- could she be :-?

[jraabe]

Talk about [highlight]Topic Drift! [/highlight]

Liteman's initial question:
"Would it be unwise to put EPS foam board under drywall and over batt insulation on the inside walls along with sheathing and foam board on the outside? Would I still need vapor/air barrier and where?"

My suggestion:
That should be a very good wall system and will likely be cost effective superinsulation for a colder climate. You would not need an additional vapor barrier as the foams do this job themselves. I would make sure the framing has time to dry since you are sealing the wall to a large extent on both sides. You will have very effectively insulated the framing with this system. If you can add 1/2" to 3/4" strapping over the outside foam or housewrap it will provide a drainage channel behind the siding and you would have an excellent wall system.

[glenn-k]

Sorry about that , John but as you may recall you were the first one to talk about insulating bats.

I may have mis-associated it with something else in my mind --- I have these little synapse mis-connection problems. :-/

[glenn-k]

I think you may have been the only one with a complete answer on that too -- you are the famous super-insulation guy.

[tc-vt]

,John

Is the permeance of expanded polystyrene low enough to be a vapor retarder/barrier and wouldn't  plastic sheeting under the drywall still be beneficial to provide a better air seal than would be provided by the drywall over EPS boards?

Since the gap between doubled wall studs can't be insulated easily, another cheap and quick way to improve the insulation of a wall assembly is to caulk between all doubled studs.

Tom

[jraabe]

I love the idea of insulating bats... Maybe they could be genetically engineered to produce a polyisocyanurate guano and the little critters could foam the walls in place flying off to the next job when the cavity is full.