Replies

1. 
   Red_dog | Jan 12, 2000 09:05am | #1

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   Roger,
   It's a good idea to put some foam on the walls. If you do this, you will want to buck your windows out with some wood the same thickness as the foam. This will keep the face of your new siding inside of the face of your windows, which is where it belongs. It helps to nail the foam sheets into the wall studs so you will know where the studs are when you go to nail the siding. If you use 2 x 8 sheets of Dow board, put 2 nails in every stud 4" from the bottom and top of the sheet. This will keep the foam snug to the sheathing and prevent the waviness that you might be concerned with. I would also think about using 3/4" T&G Dow board rather than 1" because 3/4" wood is easier to come by than 1" for the firring out of the windows. The r-value you would be losing would be, in my opinion, negligible.

   Red dog

2. 
   Guest_ | Jan 15, 2000 04:49am | #2

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   We regularly use 1/2 Duramate, taped and foamed, on the houses we build, and putting on vinyl isn't difficult. Just make sure you don't nail it TOO TIGHT! Vinyl is supposed to hang, even a little snug, but definitely not tight. We just use longer nails, and push them through the foam to the OSB before nailing.

1. 
   Guest_ | Jan 15, 2000 05:30am | #3

   *Hi, I am wondering about foam board on the outside of any structure .From what I understand you will create a vapor barrier especially if you tape it up also . Maybe in the warmer climate in the U.S.it doesn't matter .14 years ago I had a client that wanted me to install foam on the outside of his house and then vinyl siding . I wasn't sure if it was okay because of the possibility of creating a vapor barrier on the cold side of the house which is a serious no no . It can rot out the plywood and framing quite quickly . The buildings department told me that the foam was not classed as a vapor barrier . I did not get the job because I did not want to put the foam on the outside of the house . My anolgy was look at this 1/16 inch coffee cup . I can leave it on the counter for a week and it might evaporate but there will be not brown stains on the outside of the cup because the coffee won't leak through . There have been some real problems with stucco over foam because of the vapor barrier problem . The good builders in my area will not install the faom and stucco on top anymore . Up here in Toronto I have talked to 2 Home Inspectors and they say they will not even inspect a home for a possible buyer now because of all the problems that have occured . What has anyone else heard on this subject .

1. 
   Guest_ | Jan 15, 2000 05:43am | #4

   *Hi ,I am questioning the use of foam board on the outside of the house . I have always felt that there was a strong possibilty of creating a vapor barrier on the wrong side of the wall like this . I turned down a job about 15 years ago because I was not comfortable with this possibility . I did talk to the local buildings department about this and they told me the foam was not rated as a vapor barrier . But I could'd get out of my mind that if I left a foam coffee cup on the bench for a week there would be no coffee stains on the outside of the cup , it would evaporate but not diffuse through the cup as far as I could see . Most recently I have heard of many problems with stucco on top of foam .Things like 4-5 years later the walls exterior sheeting rotted away under the stucco even to the point of being structurally a bit dangerous . Recently two of my customers have told me that when they were looking for a home inspector to evaluate wheather they should buy this house and what kind of shape it was in the home inspectors started out by saying that they would not evaluate a house that had an exterior stucco on foam finish .What have other people heard about this . I am from Toronto , Canada and up here you really have to watch out for this kind of problem . I imagine everyone in the Northern U.S. has to be concerened about this also .

3. 
   Red_dog | Jan 15, 2000 06:28am | #5

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   Bill,

   Hello from across the lake outside of Rochester, N.Y. It is my understanding that Dow board has a good permeability rating and that 1 of it's primary uses is to add an air barrier & some insulative value on the exterior of the house. From what I understand, mostly from this forum, it also pushes the dew point of the wall area itself to, hopefully, outside of the sheathing. This would keep the water from condensation outside of the insulation cavity. I can't tell you much about what happens when you put stucco in front of the foam. In my opinion, the water damage found behind this stucco is the result of poor installation practices, primarily neglectful flashing.

   Red dog

1. 
   Dan_Dowling | Jan 17, 2000 06:16am | #6

   *I use the 1/2" insulation board & vinyl siding when we remodel existing homes, but I do not tape the seams. Rather we will run the board the opposite direction (horizontal vs. vertical). This will eliminate a lot of gaps. I believe that the house needs to breathe a little bit and this will allow this to happen with a minimal loss on your R factor.

4. 
   Roger_Heltonq | Jan 17, 2000 09:05pm | #7

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   I am in the design stage of my new house and would
   like to increase the insulation value by adding 1"
   foam board to the exterior maybe over OSB. Will
   installing vinyl siding as a exterior finish. Has
   anyone installed vinyl siding this way, seems like
   nailing would be very crucial as not to get a wavy
   appearance. Any sugges

5. 
   Guest_ | Jan 17, 2000 09:05pm | #8

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   Bill Clerk. Did you know that plywood is also a vapor barrier--vapor diffusionn retarder (VDR)? Millions of houses are sheathed with this vapor barrier and yet there has been no wholesale destruction of the houses as a result.GeneL.