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14 Answers

Can I use polyiso foam for interior basement wall insulation?

A recent GBA article (http://www.greenbuildingadvisor.com/community/forum/gba-pro-help/18454/w...) discussed options for internal foam insulation on a wall already with external insulation. Another article (http://www.greenbuildingadvisor.com/green-basics/rigid-foam-insulation) tells us that polyiso shouldn't be used for below-grade applications because it can absorb water. Our design includes a poured basement wall with 4" of internal XPS foam. I am concerned about external foam being mangled during backfill.

In Green building techniques | Asked By Michael Schonlau | Nov 2 10
4 Answers

Dealing with a 4" drip ledge on 4" of rigid foam on basement wall.

I have a double 2x4 construction on my main floor with an almost foot thick wall. On my basement I decided to put 4" of foam on the exterior and then I'm going to build an additional frost wall on the inside. My question is that with my 4" of foam it creates a ledge that will require flashing and will stick out further from the main floor of the house and my wife is concerned about the appearance of this, I'm looking for ideas of how to remedy this.

In General questions | Asked By Thomas Becker | Jun 12 12
6 Answers

Does basement insulation require waterproofing the concrete walls before rigid insulation?

I plan to insulate my basement walls using 2" XPS, air seal the seams, build a 2x4 wall 16" o.c., insulate with batts, and complete with drywall.

I have also been advised to waterproof the concrete walls using either Drylock or Super seal. Is that needed?

The exterior basement wall has a mirror drain and water proofing and the burrito-wrapped footing drain is tightlined to an external sump. My basement is currently dry.

In Energy efficiency and durability | Asked By Frank O | Dec 9 10
4 Answers

Rigid foam on the inside of basement walls

Per the details on the site, it shows rigid foam on the inside of the basement wall and then batts between the studs. Is there a moisture benefit of doing this? What is the real benefit of this vs batts? We do a handful of finished basements here in my area and everybody just does batts. Inspectors also require a vapor barrier inside but that is creating mold inside the wall and behind the barrier as we have seen that on jobs only a few months old that were insulated during the initial construction. I'm in northern Utah by park city so cold climate for sure.

In Energy efficiency and durability | Asked By Jake Jorgenson | Mar 20 12
2 Answers

How to get fresh air in finished basement without the condensation?

Purchasing a 1960's built home that has a "finished" basement on Long Island (mixed Humid / 4). There is forced air AC upstairs, but none downstairs in the basement. There is oil fired hot water radiators both up and down. Looking for a short-term and long-term strategy. Will eventually undertake major renovation and do a better job looking at the whole house system.

I am familiar with ERVs and HRVs, and have chosen passive fresh air strategies (both bath fan/inlet and air handler connected) in our past homes.

In Green building techniques | Asked By Bill Beasley | Jun 20 12
4 Answers

Closed-cell spray foam and Roxul insulation

Good Day,

I am building a new house in zone 6A and would like to know the pros and cons of using 2" of closed-cell spray foam along with 3" of Roxul inside the wall cavity as well as 1.5" of EPS on the exterior with a building wrap on top (furring with steel siding on top of the EPS and housewrap).

This is the method my building inspector has recommended and I want to know what everyone thinks. Thanks in advance.

In Energy efficiency and durability | Asked By wilf rellinger | Jun 18 12
14 Answers

R-13 in 2x4 walls

I have a project in north Georgia (climate zone 4), where the minimum code-prescribed R-value is R-13 for walls. I'm stumped on a couple of issues:

1. Several fiberglass insulation manufacturers have products that claim an R-13 or R-15 in a 3-1/2" wood stud wall. How do they achieve a R-15 in the same depth as they would an R-13? Do they just jam more stuff in the same volume? It seems that if it's the same basic product in either case, it's almost counterproductive to jam more stuff in the same volume, as the dead air is really doing the insulation work.

In Building Code Questions | Asked By JAMIE OKELLEY | Jun 18 12
6 Answers

Chimney Chase Condensation

Hello All,
Classic problem I believe.

I have a wood framed chimney chase which houses two 8" insulated, stainless steel metalbestos wood stove pipes and my main DWV stack. On certain days, when the inside/ outside temps, and the relative humidity are just right, I have condensation build-up and dripping from the underside of my chimney chase roof.
Construction detail:

6x10 timber rafters 36" (on center)
2 x 6 rough sawn decking (not T&G)
Grace Tri-Flex
3 layers of 3" Polyiso foam board
2x6 Sleepers 36" (on center, screwed to rafters below)
3/4" T&G OSB decking

In GBA Pro help | Asked By Dave Cummings | Feb 16 12
3 Answers

Should I get spray foam insulation applied to the outside of my flat roof?

A spray foam insulation company recommended that I have spray foam insulation applied to the outside of my roof (which is totally flat) and then coat that with a reflective material. (I can't have it sprayed in my attic because I don't really have an attic, just a 2-3 foot crawl space.) However, a roofer said that he would not recommend doing that because it would cause trouble down the line if something happened to the roof, such as a tree falling on it. I have no idea what I should do. Advice?

In GBA Pro help | Asked By Beth Dillmann | Jun 19 12
5 Answers

Anyone know of a good article on how to spray foam the attic "floor" to create a vented, unconditioned attic?

I have been looking for a how-to guide on the ins and outs of spray foaming the floor of an unconditioned. Attic. I have found a great article from fine homebuilding 2009 by Michael Chandler, but it only covers how to create a conditioned (unvented) attic. I want my attic to have foam between/over the joists w/ baffles at the edges connecting to the soffit (a vented attic), but I haven't been able to find a decent, detailed resource on how to do this. Anyone have any ideas?

In Energy efficiency and durability | Asked By Thomas Sweets | Jun 18 12
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