Contractor Talk - Professional Construction and Remodeling Forum banner
1 - 8 of 8 Posts

·
Registered
Joined
·
190 Posts
Discussion Starter · #1 ·
Common practice in these parts is to add 1-1/2" Cladmate insulation to the exterior of an older home (when residing), in an attempt to increase R-value.



STYROFOAM* CLADMATE* and STYROFOAM CLADMATE XL extruded polystyrene insulation are designed for use in walls and attics of new and retrofit applications. They reduce thermal bridging by insulating the entire wall including the wood studs. This decreases the potential for condensation within the wall cavity that can lead to moisture problems in the walls. The boards (over .5") have shiplapped edges that reduce air infiltration. STYROFOAM CLADMATE and STYROFOAM CLADMATE XL extruded polystyrene insulation meet the 1995 National Building Code's air permeance properties that make them suitable for use as an air barrier material.
The bolded line concerns me. I assume they are talking about condensation within the wall cavity that comes from the EXTERIOR of the home.
Most of these old homes are built like this: (starting from the outside)

Wood siding (which is removed)
Tar paper.
3/4" T&G boards (shiplap)
2x4 studs
3/4" T&G boards (shiplap)
Interior finish (no poly vapour barrier) - often lath and plaster or drywall with several coats of oil paint (essentially a vapour barrier)


My concern is this:

Would you be concerned about trapping moisture in the wall as a result of adding insulation to the exterior of the home (a home without an actual vapour barrier)?


I'll try to add another link here later when I have time to look for it.

Should be an interesting discussion.
 

·
Registered
Joined
·
20 Posts
What insulation to use?

I'm dealing with a similar situation. Just purchased a property in a village with a 30 year old 1000 sq ft mobile on it. Structurally in excellent condition. The previous owner had started reno so all interior walls have been removed, wiring and plumbing left in tact.The outer walls have been stripped to the studs.I intend to 'strap' the existing studs to 2x6 dimensions. Then the interior will be drywalled.The exterior will also be stripped and resided. All windows will be upgraded.
Now, I don't have 'unlimited' funds but have a 'fair' budget! What is my best course to obtain maximum 'energy efficiency'?Last few years, winters here have been getting 'milder' with temps around 25 below 0, Farenheight. We still get bouts as long as 30 days of around 40 below F. Since I intend to live there most of the year ,I want to achieve the maximum efficiency.
Any advice would be appreciated. Thanks
 

·
Registered
Joined
·
13 Posts
When dealing with homeowners that want more insulation on the exterior of their homes I push my favorite product lines. Crane Solid Core, this is a vinyl siding that adds R4-R4.5 to the exterior of your home. I just typed a huge reply and tried to post it and they wouldn't let me because I am new. So gonna keep this one short. I can't post their webaddress either so if you have question about the products or where to get them just message me. Otherwise do a search for it and read up on it. Excellent product, excellent warranty.
 

·
Banned
Joined
·
3,292 Posts
Since WA went back to 2x6 wall construction to get R-19. Because of the natural gas shortage or hike or whatever.It was common practice up until a few years ago to for 2x4 when natural gas was piped in to the home.

Now regardless 2x6 with limited variables. 2x4 is ok to use when less windows are used or the foam is used on the exterior. With the foam of course they want the framer to put it on.

However back to your question in WA I haven't seen a interior vapor barrier applied in years because of the moisture to mold problem it creates. It doesn't breath properly sealed up with poly.
So according to the experts a wall breaths better without interior vapor barrier.
Personally I would be more concerned if the house had a poly barrier when appling the exterior foam.


.
 

·
Registered
Joined
·
83 Posts
In Minnesota a vapor retarder is building code on the warm side of the wall and ceiling. In some areas they also make you caulk the areas around windows, doors and the perimeter of the wall and then attach the poly while caulking is still wet for a better seal. The reason for a vapor retarder on the warm side of a wall is so moisture does not penetrate into the insulation and wood members. A vapor retarder on the cold side of the wall seals the moisture in.
 

·
Curmudgeon
Joined
·
11,706 Posts
no, i do it now with new construction in iowa, but with a vapor barrier on the inside as well.
Losing ground.:no:
OP is now two years old :whistling
What kind of game is this anyway?
 
1 - 8 of 8 Posts
Top