Replies

1. 
   DanH | Aug 13, 2004 07:16pm | #1

   What's the foam for?

1. 
   DaveRicheson | Aug 13, 2004 08:36pm | #2

   Sounds like the fan fold stuff they sell with vinyl siding. 3/16 to 1/4" thickness. Sales literature calls it additional insulation, but IMHO it is a joke.

   Dave

1. 
   DanH | Aug 13, 2004 09:47pm | #3

   Yeah, and the reason it's used is to provide a flat surface over the existing siding. Not needed if the old siding has been stripped.

2. 
   MojoMan | Aug 13, 2004 11:23pm | #4

   Is see foam all the time under vinyl siding and always wonder about the wisdom of this in cold climates. The foam is not thick enough to keep the back side warm enough to prevent condensation of moist air escaping from the house. In practice, the foam is perforated by many nail and joints, so maybe my concern is academic.

   Al Mollitor, Sharon MA

1. 
   Richie921 | Aug 16, 2004 04:22pm | #5

   I do a lot of vinyl sising and I always use the extruded polystyrene backerboard.  We have a lot of houses in my area with the old asbestos siding.  The foam encases it and provides a smooth surface over which to side.  I've even gone over cedar shakes and gotten a smooth job.  Just don't go over 1 inch thick.  The foam doesn't support the shank of the nails and they could bend under the weight of the siding if you go thicker than 1 inch.  The R value is probably the least benefit but again,  I see that as a secondary purpose for the foam.

1. 
   DanH | Aug 16, 2004 04:47pm | #6

   Right. The foam board is there to provide a smooth surface over old siding, and is unnecessary if the old siding has been removed.

3. 
   maverick | Aug 16, 2004 11:14pm | #7

   I agree, forget the foam if you are stripping the wood siding. How about trading the price of the foam board for the Tyvek.

1. 
   DanH | Aug 17, 2004 12:37am | #8

   Yeah, Tyvek is really worth it, especially if you live in snow country. Can effectively improve "insulation" better than several inches of foam, by cutting out air leakage.

   Since it's DIY, take the time to tape around windows and doors, tape seams, etc. (Regular contractors generally just do a half-assed job at this at best, but a little extra effort on your part can make a world of difference.)

1. 
   maverick | Aug 17, 2004 04:00am | #9

   I agree, most people in the trade never heard of tyvek tape or would'nt pay ten bucks a roll.

4. 
   dIrishInMe | Aug 17, 2004 04:17am | #10

   Here is the main thing you need to know... Vinyl siding is not water proof - as you know you gap it at the ends of the panels, etc.  So, it is VERY important to create a secondayr rain screen behind the vinyl.  Builders felt will work fine, but it is unlikely that on a house of that age, the felt is in good enough condition to be considered a secondary weather barrier.  Maybe the foam would serve this purpose, especially if it were taped up with Tyvek tape, I'm not sure.  Just realisze that water will get behind the siding around the windows and doors, and at the house corners, so make a plan to deal with it. 
    

   Matt