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1 Answer

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


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

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

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
2 Answers

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

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

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
4 Answers

Our firm is developing a range of sustainable wall section details for our clients to select from. For several variations, we have 4" of rigid polyisocyanurate foam outside the structure. Along the walls, screws through 1x4 strapping fix the foam back to the studs. At the corners, however, this becomes difficult. What do you suggest? Any clarification would be helpful.

In Green building techniques | Asked By Samuel Ganton | Oct 6 11
7 Answers

I got another email from one of the GBAGreenBuildingAdvisor.com regulars asking if I could change the comment settings to display the newest comment at the top rather than the oldest comment at the top of the thread.

After clicking a few boxes, i discovered that yes, I can change that fairly easily.

I suspect that some people will be unhappy with this, so I'm going to take a poll:

In General questions | Asked By Daniel Morrison | Sep 30 11
6 Answers

Our county is considering creating a Energy Efficiency requirement of a HERS 70 on all new residential construction. If we follow the IECC 2009, which our state has adopted, the prescriptive path is presumed to achieve a HERS index of 89. The question posed is how much more it will cost a builder, including HERS analysis, testing, and verification, to get to a 70.

In Building Code Questions | Asked By kim shanahan | Oct 5 11
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