# More insulation questions



## cc-rider (Jul 29, 2003)

All I know is that I want to get as much insulation value in my house as I reasonably can! 

I'm building with 2X6 studs.  The exterior will be sheathed with plywood or OSB, and then a layer of tyvec, and then sided with board and batten. Can I put a layer of foam between the tyvec and the interior (stud-side) sheathing? Would it serve any purpose? Would it cause a problem being on the "cold" side of the wall? Moisture on the inside?

I have some free kraft-faced insulation for the walls, so could use that, but I really like the idea of using the foil faced iso-foam (can't remember the word) somewhere. Unfortunately, I think you need a 1/4" gap between it and anything else and I'm not sure how to do that! 

If I use it outside of the sheathing, between the sheathing and board and batten, I could eliminate the tyvec and foam, I guess, but how do I get the gap? And would having something so waterproof on the OUTSIDE of the house (the cold side) cause moisture in the walls?? (Same as foam??)

Instead of fiberglass on the inside, I was also toying with the idea of blown insulation - dense packed, or sprayed foam, or the new "spider" insulation which is blown, but looks like foam. If I do that, can I still somehow use the foil-faced stuff? If so, how???? 

I just like the idea of having the foil to reflect the heat. But maybe that's all hype and not necessary.

Any ideas???


----------



## cougargnw (Aug 6, 2007)

My first post over here, I usaully hangout in survival and prep. 
I design roofs for a living and spent 5 years as a mason to give you a little background on my answer. The foam board on the outside of the home never appealed to me. The R value is not worth the cost in supplies. A good wrapping of tyvek an the 6 inch studs filled to capacity should give you a great barrier agianst the outside.
As for the foam insulation,I thought about this for my house. Then I thought about trying to fish a wire through it if I wanted another circuit somewhere. Stick with the cellulose or standard glass. The stuff works great.

edited due to a [email protected] keyboard


----------



## Explorer (Dec 2, 2003)

I my opinion it is hard to have too much insulation. Different siding requires different methods. I have a stucco exterior, tar paper, then 1 1/2 Styrofoam, 5/8 OSB and paper backed insulation between the 2x6 studs on 16" centers. If I did it over, I would get blown in insulation as it provides for better cavity filling. Before the stud insulation every little crack was filled with that foam in a can, almost 60 cans. My placed is very air tight and uses way less energy that just about any other house in the area according to the gas and electric company.


----------



## trapperJim (Jan 24, 2008)

I don't have any experience with blown in insulation but am not a fan of styrofoam. As mentioned - the R value isn't worth the cost as far as I'm concerned. A GOOD fiberglass job will do a nice job of insulating. I tuck a little extra piece behind the outlet boxes and tape around all the boxes with tyvek tape. This totally eliminates any drafts that may try to sneak in through and around outlet boxes. One thing that I am VERY impressed with is Tek Foil. That is bubble wrap laminated between two layers of foil. I have that sandwiched between the floor joist and the sub floor of my heated fur shed with no other insulation in the floor. I don't even have T&G plywood on the floor and there are NO drafts and I feel NO tempature change when I squat down near the floor. The insulating abilities of this stuff is outstanding. I have never used it on the walls but I will definately be using it in the floor of my next home. My home has T&G plywood sub floor, rosin paper, 3/4" finish floor with 6" fiberglass beneath it and I can feel more tmpature change from head height to floor than I can in my shed with just 1 layer of 5/8 square edge plywood with 1 layer of tek foil.


----------



## TNHermit (Jul 14, 2005)

Before you worry about insutaltions the first thing you want to do is make your place draft proof. I don't care how much insulation you have if there are drafts around the windows and doors and corners the place will be cold. If I had a choice I would foam the studs and put an 1" foam with tyvek over it on the outside. They make a fish line with a type of drill bit on it to get thorugh the foam if you want to fish a new line.

I don't like fiberglass. Nobody has ever told me how you can use it for a filter for air to go through and then at the same time call it insulation. It has to trap DEAD air.

I like the tek foil too but you get all kinds of opinions on that. I'm about to put it to the test this year.


----------



## SolarGary (Sep 8, 2005)

Hi,

The whole wall insulation calculator that takes into account thermal bridging through the studs gives:

2X6 wall with R19 insulation, no foam board = R14.2
Same with 1 inch of foam board = R18.35

So, a pretty good increase. Its particularly effective because it eliminates the thermal bridging of the wood studs. Its better than this if you use the polyiso, because it has a higher R value per inch than the polystyrene the calculator assumes -- I think this would make the R18.35 an R20.35.

This is the calculator:
http://www.ornl.gov/sci/roofs+walls/AWT/InteractiveCalculators/rvalueinfo.htm


I'd go with the blown cellulose over FG -- reasons in this section:
http://www.builditsolar.com/Projects/Conservation/conservation.htm#Insulating
Look for the "Convection Losses in Loose Fill Fiberglass" article.

The book thats mentioned called "Insulate and Weatherize" by Harley is really good.

Here is another idea for getting more R for not a lot more money:
http://www.builditsolar.com/Projects/Conservation/MooneyWall/MooneyWall.htm

If you look at the history of recommended insulation levels, they keep going up over time -- I think that with the way fuel prices are going to go, the recommended R values are likely to go up even faster in coming years. And, its tough to make changes after you build the wall 

Gary



Gary


----------



## cc-rider (Jul 29, 2003)

SolarGary said:


> Its better than this if you use the polyiso, because it has a higher R value per inch than the polystyrene the calculator assumes -- I think this would make the R18.35 an R20.35.
> Gary


Where would you put the foil-faced polyiso? If you put it on the OUTSIDE of the sheathing (in the place of tyvec), does it cause a problem by not letting moisture out of the house since it's on the "cold" side?


----------



## WisJim (Jan 14, 2004)

cc-rider said:


> Where would you put the foil-faced polyiso? If you put it on the OUTSIDE of the sheathing (in the place of tyvec), does it cause a problem by not letting moisture out of the house since it's on the "cold" side?


Yes, it can cause rotting/moisture problems UNLESS there is an excellent properly installed vapor barrier on the inside of the wall. And I think that there still can e problems with the outside foam. I have seen problems with houses that were resided and had even the thin foam installed under the new siding. Five, 10, or even 20 years later, moisture related problems start to show up.


----------



## SolarGary (Sep 8, 2005)

cc-rider said:


> Where would you put the foil-faced polyiso? If you put it on the OUTSIDE of the sheathing (in the place of tyvec), does it cause a problem by not letting moisture out of the house since it's on the "cold" side?


Hi,
One way is to use it instead of sheathing -- in this case, you need to use the let in metal diagonal braces on each wall to provide the shearing strength that the plywood or OSB siding would have provided. You can also add it over the sheathing. 

Both the polyiso (with metal foil faces) and the ploystyrene rigid insulation board (e.g. the blue stuff or pink stuff or white stuff) are good vapor barriers. So, any potential moisture problem would be the same with any of them (I think).
The whole business about moisture problems in walls caused by things like insulation board on the outside seems to be in some flux. It depends on the climate, and on which set of experts you read. 

Here is an article in Fine Homebuilding that might be worth looking at:
Save Energy With Rigid-Foam Insulation, Fine Homebuilding, Issue 181, Sept 2006. You can downwload this at their website, but you have to do the electronic subscription -- I think you can sign up for just one month at $6 -- its a great magazine, and most (all?) of their articles from past issues are on line.
http://www.builditsolar.com/References/FineHomeBuildingArticles.htm

I would post the question about potential for moisture problems with rigid foamboard insulation on the "Breaktime" forum at Fine Homebuilding -- there are a lot of people in the construction trade and people in the building sciences there. I'd like to hear what they say 
http://www.taunton.com/thetauntonpress/forums.asp

Gary


----------



## cc-rider (Jul 29, 2003)

I posted there. Thanks!!!! Looks like a lot of good information on that site. You can tell that they aren't homesteaders, however.


----------

