Q&A: A Forum for Green Building Experts and Beginners

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7 Answers
Insulating a steel building used as a home

I recently erected a red iron framed steel building with 26 gauge steel panels on the exterior walls. During the planning stages, I was going to apply closed cell foam. Unfortunately, I am no longer able to afford this option. I am now looking at using fiberglass batts. My plans are to stick frame the interior walls with standard wood 2x4 studs. This will create a 12" deep wall cavity in which to insulate. My thought is to install batts of EcoTouch R30 in the steel wall cavity and R13 in the 2x4 stud interior walls. This will yield R43 in my walls.

In Energy efficiency and durability | Asked By Dwayne Cormier | Oct 6 11
1 Answer
Does roofing tar paper act as a vapor barrier and how many layers?

I am re-roofing a cathedral ceiling house. Looking up it has 2" tongue/grove pine resting on 4x6 joist beams (5') centers running to a ridge beam. I have done the tear off - and the 2" pine is the ceiling on the bottom side and existing decking on the top side. The pine is the only thing up there now. It's a tight fit. 3/12 pitch - Southern Michigan.
I want to insulate, ventilate if necessary, and re-roof.
What materials should I use?
What is the order of the layers needed?
Can I lay down a layer of roofing paper on the top of the pine to protect it while I make the decisions

In General questions | Asked By craig askins | Oct 11 11
1 Answer
XPS and Its Long Term Efficacy

There are a couple of comments that stick with me regarding XPS efficacy over the long haul:
1. A contractor uncovered foam insulation he had installed approximately 10-15 years ago on a house. He found gaps between the foam panels due to shrinkage over time.
2. Martin Holladay interviewed a representative from a major XPS manufacturer who said they were constantly reformulating their XPS products which could mean further unforeseen problems.
The questions that arise from these comments:

In Energy efficiency and durability | Asked By HORST SCHMIDT | Oct 11 11
12 Answers
How do I find a contractor that does external insulation?

Background

I'm a fairly new home owner in zone 5A (NY, 40 miles north of NYC). My existing house is about 60yo and appears to have almost no insulation . The siding is mostly white-painted thick cedar shakes and a bit of board+batten. It's a quirky house built by the owner two generations ago and surprises abound.

In Energy efficiency and durability | Asked By Jason Crawford | Sep 22 11
1 Answer
Retrofitting an insulated flat ceiling in a room with an existing cathedral ceiling

We’re looking at 10 yr old tract houses to remodel and live in. But we hate the cathedralized ceilings which show up even in houses of 1700 s.f. -- a local builder fad at the time. First, I know cathedrals aren’t good for energy efficiency with 4-6” of glass batts and no air sealing. Second, they may look grand in a big house but in a small living room or 12x12 bedroom they feel like an elevator shaft. We don’t like them … but the houses are cheap enough to think about.

In Green building techniques | Asked By JoeW N GA Zone 3A | Oct 10 11
7 Answers
Stone foundation floor insulation

We have purchased a 100yr old home in central Massachusetts with a stone foundation. The basement is used solely for the purpose of holding the heating and hot water systems. We are in the process of addressing significant water problems. To date we have installed sump pumps, air exchange ventilation system, dehumidifer and we have begun parging the stone walls with hydraulic cement. Long term plans are to regrade the exterior and divert roof water away from the building. That being said we believe the basement will never be entirely dry and the cost to do so is prohibitive.

In GBA Pro help | Asked By Michael Peluso | Oct 9 11
12 Answers
Structural Insulated Panel (SIP) roof decay

I have a BensonWood timber frame in Vt that is only 8 years old with significant panel roof decay. So much so that my standing-seam metal roof has begun to rust from the inside out. There is evidence of SIP seam failure in several places below the standing-seam metal roof. Is it likely this was the cause? It is a hot roof.

In General questions | Asked By gregory raith | Oct 3 11
2 Answers
ERV/HRV installations using forced-air space heating ducts

I am a HERS rater and EE building consultant. 40-50% of the new constructon I see utilizes an ERV/HRV for whole house ventilation. Of those, (roughly) half of those are installed in houses using ductwork for space heating and/or cooling. Of those many have the ERV/HRV houseside ports ducted into the return side of the duct. My question is: How reliable is the airflow strength of the ERV/HRV when the ERV is called to run, but the air handler unit fan is not running.

In GBA Pro help | Asked By Kevin Hanlon | Oct 7 11
2 Answers
Using WUFI to check wall moisture

I'm doing a number of highly insulated retrofit projects, and am concerned about long-term moisture in wall and ceiling cavities. I've had a brief intro to WUFI, the hygrothermic analysis tool, and am using v.5.1 (non-commercial) on my projects. But there are some inputs on the Surface Transfer Coefficient page that make a big difference in performance, but aren't intuitive or explained. They are:

-Short-wave Radiation Absorptivity (should we use "no absorption" or try to use the closest value?)

In Energy efficiency and durability | Asked By Tom Bassett-Dilley | Oct 7 11
3 Answers
Looking for anyone that can explain why mold occurred on the bottom side of the roof deck overhang, between the rafter tails.

It is an open overhang, so no soffit. Black roof. The mold is on the back side of 3/4" exterior plywood which replaced original 80 year old deck 11 years ago. This playwood was painted with oil based Sikkens Rubbol DEK. This mold is occurring on all orientations of the house. It is a gambrel roof, dutch colonial style. A detached garage with the same style overhang has the original wood deck and has no mold. I originally thought that the sun was driving water vapor slowly through the shingles, wood deck and it condensed on the back side.

In Energy efficiency and durability | Asked By mark faultersack | Sep 28 11
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