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!

1 Answer

Can a skylight ever be energy positive?


I'm curious as to whether skylights are always net losers, or if one could be favorable given the right conditions. In general they seem to be avoided due to the heat gain potential and nighttime loses.

In PassivHaus | Asked By Ryan Griffin | Nov 18 14
8 Answers

Options for temporary heat in MN winter

I'm interested in the opinions of builders and others regarding temporary heat during contruction. My southern MN home is enclosed, windows in, and exterior walls spray foamed. Not as air tight as it will be, but pretty tight nevertheless.

Options include:
1. electric resistance space heat - pros: convenient, no fumes cons: most costly option per BTU, safety concerns for unattended heaters
2. portable kerosene heaters - pros: have unit available cons: fumes (about choked me when used last Saturday), need to refill reservoir tank every 36hr

In Mechanicals | Asked By Kent Jeffery | Nov 18 14
8 Answers

Half insulating a stone basement?

It's been a long road and we are almost ready to move in to our project. I tackled the two part plaster myself with nice results but now it's getting cold. My basement is typical fieldstone 1880 style and the house is in Zone 6b. The foundation is about 4' underground and 2' exposed with a 10x10" fir sill plate beam. I have read the building science articles about completely modifying the basement but that's not in the cards and is another massively expensive project I cannot tackle at the moment.

In Energy efficiency and durability | Asked By Geoffrey Cook | Oct 31 14
3 Answers

Are tar paper and Tyvek a vapor trap?

Can you please set me straight because I am getting different points of view on this. My home is 40 years old, has the old type of sheathing, a layer of tar paper and then T1 11 siding. In patching one side of the house, I have put 1/2 inch foam board over the T1 11 and then Tyvek. Is this a vapor trap? If so, what part of it is?

Is the use of tar paper and then a layer of Tyvek on the outside of the T1 11 a vapor trap?

Is the use of rigid foam board a vapor trap?

Thanks so much!

In Green building techniques | Asked By CK North | Nov 16 14
8 Answers

Moisture in exterior wall

I have posted questions several times regarding my double wall assembly on a house that I am in the process of building in a very cold climate. At the present time, the drywall is being finished and my air exchange system is not yet running as I don't want the system on when there is a lot of dust. I am running a dehumidifier which is taking out a lot of moisture from the air but certainly not enough. I am heating with electric heaters, keeping the house around 64-70F. My humidity is ~50-60% as a result of the new construction and the mudding that is happening on the drywall.

In GBA Pro help | Asked By Matthew Michaud | Nov 17 14
2 Answers

ERV - where does the moisture go?

I understand the difference betwen an HRV and an ERV - that the HRV transfers heat between the incoming and outgoing air while an ERV transfers both heat and moisture. I am puzzled as to how, in a house with an ERV, the moisture generated by bathrooms, laundry, people, dogs etc actually leaves the building if it is transferred to the incoming airflow ? Also, what stops odors being transferred between outgoing and incoming air ? I haven't mentioned cooking because I'm assuming a range hood with its own make-up air will be used.


In Mechanicals | Asked By Peter Hastings | Nov 18 14
5 Answers

Minisplits in the humid southeast?

I'm currently working on design for a house in the southeast, on the border between climate zones 3 and 4 (officially 4). Tight site, 700sf footprint, 3 floors over a walk out, unfinished but minimally conditioned basement.

Wall composition isn't settled yet, though the minimum is likely 2x6 studs with blown cellulose or open cell foam and 2" exterior xps. Basement is possibly thermomass if the numbers shake out OK. Given the small footprint and envelope, I'm hopeful that we can opt for decent walls, roof, and windows.

In Mechanicals | Asked By Chris B | Nov 17 14
13 Answers

What are the potential problems in an open-cell foam sealed attic when voids and inconsistencies exist?

Along with the open-cell insulation, a radiant barrier roof sheathing was utilized. In most cases, half of the roof framing member (12" TGI truss & 2" X 10" out-looker) surfaces are not encapsulated. There are potential areas where exterior wood framed attic walls are not insulated or sealed off from the attic space. The foam insulation was applied after A/C duct and Can lighting fixtures were in place between the framing members. Most ceilings are cathedral with a tongue & groove wood finish.

In Green products and materials | Asked By Michael King | Nov 11 14
2 Answers

When installing fiberglass batts which is the correct method?

I've always folded the paper flanges over each other on the stud & stapled.
I've seen some videos on You tube from major companies showing them stapling the flanges on the inside of the studs. It doesn't seem right to me. It compresses the batt, & seems like it allows air leakage.I've always thought that if the flanges overlapped you get abetter seal & vapor barrier.
Which is the best way?

In Energy efficiency and durability | Asked By roger steinbrink | Nov 17 14
26 Answers

Imagine a house fire without fire. You better read this article energy misers!

Take the time today to read, study, and learn as much as you can about today’s modern building construction, the impact of ventilation on residential structures, and many of the other topics available through UL-FSRI. Be prepared to change, alter, or adapt your tactics when necessary.

In Green building techniques | Asked By Richard Beyer | Nov 14 14
Register for a free account and join the conversation

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