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

Q & A Instructions

[Click map to enlarge]

The GBAGreenBuildingAdvisor.com web site has a wealth of articles on a wide variety of construction topics. Before posting your question, you may want to check out the articles on this page: How To Do Everything. You just might discover an article there that provides the information you seek.

Please register for a free account or sign in to ask and answer green building questions.

If you want to post a question, the usual rules of courtesy apply:
1. Be nice.
2. If you can't be nice, be polite.
3. If you can't be nice or polite — well, please be brief.

To attach a photo or illustration: Under the box labeled “More explanation,” look for the words “File attachments.” Click that, and you should be able to attach a photo.

Thanks for joining the conversation!


2 Answers

I am working on a single family house in Climate Zone 5 in New York State.

The first floor is a suspended concrete slab with radiant heat over wood framing. The basement is totally buried with the exception of the top 6". It's covered in 2" of rigid insulation. It will be heated but to a lower temperature than the first floor.The only opening into the basement is a bilco door.

I had originally specified 1" white Dow to be used under the first floor joists but am wondering if I can specify instead one of the radiant barrier materials in the interests of economy. Thanks.

In Energy efficiency and durability | Asked By Linda Gatter | Feb 7 13
2 Answers

Vapor barriers inside AND outside of unvented crawl space?

I have been trying to figure something out for days. Maybe you can provide some clarity.

If I am building an unvented crawl space, and have an interior vapor barrier on the ground and sealed to the stem wall, with rigid insulation over it, do I need to have a vapor barrier on the EXTERIOR of the foundation wall, as well?

Do I even need to brush asphalt on the exterior CMU or do I want it to breathe?
Thanks so much!

In Energy efficiency and durability | Asked By Beyhan Trock | Feb 7 13
15 Answers

Would this building envelope work? Zone 4A in Japan

Thanks to GBA members' answers I received to an earlier question ( www.greenbuildingadvisor.com/community/forum/energy-efficiency-and-durab... ), I have decided to abandon local building practices. I am aiming to build a well-insulated & airtight 600 square foot house for my family.

In General questions | Asked By Eric Matsuzawa | Jan 26 13
2 Answers

How long should VOCs linger after removal of the source?

I purchased a home n Florida built in 2005 which I discovered had a VOC problem after closing. There is a aromatic sort of piney smell in the house that attaches to anything left in the house for more than a few hours. The house is empty of any furnishings, had engineered wood floors glued to the slab over 50% of the house with tile/carpeting in the rest. The kitchen and bath have cherry wood cabinetry and there are plastic blinds on the windows. I removed one cabinetry box from the home and didn't notice the odor. The odor doesn't extend into the attached garage.

In General questions | Asked By Mary Loughran | Feb 7 13
3 Answers

Can pressure-treated lumber be used inside of a dwelling as framing material?

...such as where basement partitions on bottom plates of a wall or where concrete meets lumber, and what type of barrier is required between lumber and concrete?

In Building Code Questions | Asked By John Poulette | Feb 7 13
15 Answers

Ineffectiveness of increasing R-value with more than 4 in. of closed-cell spray foam?

I have been told a number of times that using more than 4" of cc spray foam (in a wall or roof assembly) has little value at increasing r-value. In other words, does using more than 4" not have a linear increase in r-value? The reason I ask is b/c I need the recommended r-35 against the bottom of my roof sheathing (with blown-in cellulose in the remainder of my cathedral truss) to prevent the roof sheathing to dip below the dew point and create condensation. Any thoughts? Thanks.

In GBA Pro help | Asked By Matthew Michaud | Feb 2 13
4 Answers

Controllng infiltration through entry way doors

In my caulked-to-death cottage, there is annooying air infiltration around my front and back doors. The inflow increases when exhaust fans are turned on, the negative pressure results in the opening up/softening the connection and allowing air in.

I am surprised not to be able to find much info on how to seal entryway doors. I can't find any lock-sets or after-market door sealing solutions that convince me of their effectiveness.

In Energy efficiency and durability | Asked By Oak Orchard | Feb 5 13
8 Answers

I read the good article on building a vaulted ceiling — too late

I read the good article on building a vaulted ceiling. However, that is too late for me since I already have vaulted ceilings throughout my house.

In General questions | Asked By Gene Byrd | Jan 28 13
1 Answer

How to insulate the ceiling/roof?

I have a chalet-style house in Virginia which needs insulation. Built about 1970 as a Linden model, it is hard to heat in the winter. We installed a propane fireplace to help the heat pumps in the two stories plus basement. Summers are not such a problem because the surrounding trees give shade.

In General questions | Asked By robert thomas | Feb 6 13
4 Answers

Bath fans: ceiling-mount or inline?

On my new build currently under construction, I am trying to determine which route to go with the bath fans. I have a 100sqft bath and a 65 sqft bath. The 2 vent locations are either a gable end or straight up through the roof. They will go in a unconditioned vented attic space with r60 blown insulation.

I much prefer the gable, however the closest gable is about a 25' duct run for the fan. I am thinking if I go this route an inline fan may be the better solution, such as one from Fantech.

In Mechanicals | Asked By Jesse Lizer | Feb 5 13
Register for a free account and join the conversation


Get a free account and join the conversation!
Become a GBA PRO!