Replies

1. GBA Editor
   Martin Holladay | May 14, 2010 11:35am | #1

   Jon,
   1. Best siding? There is no answer to that question. Choose whatever siding you want.

   2, Best vapor barrier? None. Instead, use a vapor retarder (for example, vapor-retarding paint).

   3. Best insulation? On a siding replacement job, I'd say rigid foam (either EPS, XPS, or polyiso) installed on the exterior side of the existing sheathing.

2. 
   jon | May 14, 2010 12:05pm | #2

   Let me catch up to you, Martin. I've been reading some older post here but I'd like to confirm a couple points. Not sure what I will find underneath the old siding as far as sheathing but I suspect whatever it is it will be there. When you say no VB is that because the rigid foam is enough? (No felt paper either) Is it wise to use the reflective on one side type?
   Do I simply use long screws to attach the new siding through the foam? Do I need a gap for circulation like I would in ceiling application?

3. GBA Editor
   Martin Holladay | May 14, 2010 12:14pm | #3

   Jon,
   It sounds like you need to do some basic studying about vapor barriers and vapor retarders. You might start with these two articles:

   Vapor Retarders and Vapor Barriers

   Forget Vapor Diffusion — Stop the Air Leaks!

   There is no need for exterior foam sheathing to have foil facing.

   The exterior foam should be tacked up with any old fasteners and then secured permanently by 1x3 or 1x4 vertical furring strips screwed through the foam to the underlying studs. These vertical furring strips create a rainscreen gap between your siding and your sheathing or foam.

4. 
   jon | May 14, 2010 12:44pm | #4

   Thanks Martin, I appreciate this.

5. 
   Lee | Jun 19, 2010 09:02pm | #5

   what is the best exterior foam including the best rating, use before placing the vinyl siding / want to avoid molds/ moisture behind the vinyl siding. I want durability and reliability/ thanks