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21 Answers

Roxul for crawlspace stemwall? And a related detail.

Basic question: Is Roxul Comfortboard a suitable substitute for the usual interior rigid foam insulation in retrofitting a crawlspace? (House in zone 5, crawlspace floor is about a foot below outside grade, walls are CMU. drainage is very good. I do plan to use cut'n'cobble XPS in the rim joist area, to ensure good air seal. Homeowner very opposed to foam if it's not necessary, which has led me to look into Roxul.)

In Green building techniques | Asked By Andy Chappell-Dick | Sep 4 14
39 Answers

High levels of carbon dioxide in house

My house has high levels of CO2 / carbon dioxide, every room is between 1100 ppm to 1200 ppm according to an air quality test I had. There are only 2 grown occupants and it's a 1000 sq. ft. brick house. No pets or plants, gas stove / furnace / water heater.

The basement was the only area that had between 900-1,000 ppm of CO2. I've read ASHRAE likes to see under 1000 ppm of CO2. We do have headaches & drowsiness but aren't sure if it's strictly from CO2. For reference, our CO (carbon monoxide) numbers were all under 2 ppm.

In General questions | Asked By Jeff Watson | Mar 9 14
4 Answers

Why doesn't RESNET put more weight on air sealing in their proprietary formula for determining the HERS Index of a new home?

I recently was granted a HERS rating of 40 for my new ENERGY STAR Vers 3.1 home without renewables. The blower door test was CFM@50 Pascals = 95 and ACH50 = 0.27. My HERS Rater told me that the blower door test data has a minimal affect on the overall RESNET HERS rating. In my opinion and that of many professionals, air infiltration is the single most important factor affecting the energy efficiency of a new home. A new home with high R values for the walls and ceiling may be very energy inefficient if its air sealing is poor.

In Energy efficiency and durability | Asked By JOSEPH POLAND | Sep 7 14
4 Answers

Spray foam - how thick to air seal a rim joist?

What is the minimum thickness of spray foam on a rim joist for effective air sealing? I'm using a disposable 2 part 200 board foot kit.

In General questions | Asked By Walter Gayeski | Sep 4 14
8 Answers

Tamarack Cape vent dampers

Hello all - I'm a bit intrigued by Tamarack cape dampers - I've searched here and found a couple of threads that include some mention of these units, as possible solutions to issues in specific applications (wood stove OAK, and HVAC duct). I wonder if anyone has any experience with this style of damper in a bath fan exhaust? Apparently they've been around for @ 5 years. Rated to 160 deg F but I have no idea how they would perform under extreme cold conditions (such as what this winter has brought us). Any insights or comments are greatly appreciated. Thanks....

In General questions | Asked By Randy Toni | Mar 26 14
6 Answers

Used XPS or new EPS for outer layer of over roof insulation

I can get reclaimed 3" XPS and 4" ISO insulation locally for less than half the cost of new material. I am planning to reroof and put 4" of ISO over the roof deck then a second layer of foam above that. I am in zone 5B and need at least R-20 above the deck to control the dewpoint (quick thank you to Martin for providing a place and tools to learn about these things).

Although XPS has a high GWP this is used so should I care, or should I get new nailbase with EPS?


In Energy efficiency and durability | Asked By Eric West | Sep 5 14
4 Answers

Do fans help to dry objects when dehumidifier is running?

Project is a nonprofit archives building in Maharastra State, India. It has a double wall of thick masonry to provide a thermos effect that is effective at evening both annual and diurnal temperature fluctuation. The inner room (that holds the artifacts) has no opening but a door and egress, and is very airtight. No human needs, so no mechanical ventilation.

Humidity control remains an issue. Currently a small portable is proving almost adequate. Heating and cooling is not necessary.

In GBA Pro help | Asked By David McNeely | Sep 6 14
3 Answers

Open-cell spray foam vs. Roxul

Again I am asking insulation questions. I have a bid for a full foam compliment in my new construction home. They want to do 4" of open cell in the exterior walls trouble is my walls are 2x6 and it just doesn't make sense to leave that area open to me plus the foam performs best at 4" thick so I understand the cost difference for payback on no the extra inch is tough to justify.

R-14 in the stud bays with the r-9 outside with polyiso just seems a little short on r value to me??? Seems like I can do better.

In Energy efficiency and durability | Asked By Anthony Hughes | Sep 4 14
8 Answers

Humidity being trapped between an inside vapor barrier and OSB?

As a potential solution for concern about OSB being a vapor barrier, and all the related potential problems for humidity being trapped between the inside vapor barrier and the OSB, an architect has recommended to me to drill 1/2-inch holes every 8 inches throughout the OSB panels to allow humidity to escape to the outside, while the housewrap will prevent water from entering into the OSB.

I would like you to comment on the value of this recommendation.

Thank you in advance for your help,

Pierre Gingras

In GBA Pro help | Asked By Pierre Gingras | Sep 7 14
2 Answers

Masonry cement odor

We installed a Boral synthetic stone surround using Tolteca type s masonry cement at an interior wall fireplace renovation. After 6 months there is still an odor coming from the surround. That wet mud, almost gym sock smell that varies in intensity with weather changes. Boral says it cannot be the stone and the mason says he has no history or reports of this odor. We have had environmental testing for VOC, MVOC, swab, and mold. No issues, but smell was corroborated by them.
What can we do except rip it out?

In General questions | Asked By John Bertelsen | Sep 6 14
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