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2 Answers

Vented crawl space insulation, Southern California

I'm in the early stages of rebuilding my house, which happens to have a ventilated crawl space. I believe I'm in climate zone 3B, and my project manager is encouraging me to simply use fiberglass batt between the floor joists to achieve the required R-13 insulation.

In Energy efficiency and durability | Asked By Mike Simanyi | Sep 8 14
12 Answers

Rainscreen siding with a very large gap

Reading about rainscreen siding systems it seems that the recommended gaps are typically 1/2" to 3/4" between the housewrap and and the back of the siding. Is there any reason why one couldn't do a very large gap using thicker furring material? Maybe around 3" or 4" between the siding and the sheathing for architectural reasons on a remodel? Would there be problems with having that large of a gap?

In Green building techniques | Asked By Kevin Hardy | Jul 26 14
5 Answers

Foam, cellulose, sealing, or none of the above? Benefits outweigh risks?

Hi – I'm a homeowner who has spent a ton of time reading a few dozen threads here (invaluable), other posts/articles elsewhere and have arrived at a crossroads…open to advice and/or questions I should be thinking about to help me arrive at a decision. I can provide as many details as needed on my energy audit, house location/construction/details, monthly energy expenses, etc. if necessary.

It boils down to this (Note: no need to use attic for storage/living space)-
1. Use blown-in cellulose in attic, lots of air sealing, CC foam in cantilevers/rim joist

In Energy efficiency and durability | Asked By George G | Sep 8 14
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
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