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

[Click map to enlarge]

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

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!


7 Answers

Airtightness Goals

I think that we should raise or SET the bar for air tightness goals.

What is the bar? Is there an Energy Star standard? A LEED standard?

Should it be the Building America Westford Metric?
What is the Westford metric? is it 1.5 Air changes per Hour at 50p or is it 3 ACH @ 50?

How about Passivhaus Standards? 0.6 ACH50

How many out there are surpassing the Westford Metric?

Is any one besides Passive House USA meeting Passive house airtightness standards?

What is your best blower door result and how did you achieve your air barrier?

In General questions | Asked By John Brooks | Apr 25 09
1 Answer

2. What makes it a good choice for the environment?

Just need this for my Highschool Science project! Thank you Soooooo much!!!!!

In General questions | Asked By Rylee Godsoe | Jan 4 13
3 Answers

What is the thermal effectiveness of an exposed batt in a flash-and-batt hot roof?

First, this is for residences in Climate zone 5. We have seen several insulation companies recommend a flash and batt system to insulate a roof system in an unfinished attic space. The recommendation is for 3" of CC foam (R-20 to R-23) covered by an R-21 unfaced fiberglass batt for a total nominal R value of ~ R-40. The fiberglass batt is visible from the unfinished attic and according to the insulation company meets the dual role of an ignition barrier and an R-21 thermal break .

In GBA Pro help | Asked By Jeffrey Rhodin | Dec 27 12
9 Answers

Frost & Thermal bridging?

We have 2 x 8 exterior walls with 2 x 4 staggered stud framing. Standard plywood sheathing with hardie board siding. Full 2 x 8 on plates and at openings so we are a bit surprised to find the same frost pattern on the wall as the rest of the standard framed 2 x 6 framed houses in the neighborhood. There must also be a dewpoint factor involved here? This isn't what I've been led to believe in the building science classes I've taken... Any gurus out there that can shed some light on this?

In Energy efficiency and durability | Asked By Kent Mitchell | Jan 3 13
2 Answers

Whether it's worth removing Sheetrock in closets to spray foam

Dear all, I have a Cape Cod and plan on insulating the second floor by air sealing with 2 inches of spray foam and then finishing with 3.5 inches of Ultra Touch cotton batts to fill the 6 inch rafters.

There are a few closets that are sheetrocked and will take a great effort to remove. Since the closets have doors thus preventing most of warm air to condense against the roof after dense packing with cellulose should I have any concerns? Ideally I would like to air seal whole of second floor but ripping out all the Sheetrock is a large task.

Mike

In General questions | Asked By Michael H. | Jan 3 13
6 Answers

What is your opinion of using LOW-E reflective insulation for slab insulation?

I'm starting a home in South Eastern Wa. State. It will have a daylight basement. I was going to use for slab insulation LOW-E Reflective Insulation. Has anyone used that material before and what is your opinion?

The material is !/4 " foam foil.

In General questions | Asked By Dan Easton | Jan 1 13
3 Answers

HRV/Central Fan filtration

Hi,
This question was inspired by the Q&A from Cathy who wanted to know about affordable alternatives to HRVs.
We recently bought a house with a bathroom fan unit we can set to run constantly or when humidity reaches a certain level. There's a separate fresh air intake on the side of the house that flows into the HVAC system, and the fresh air gets minimally filtered through the furnace air filter.

In Mechanicals | Asked By Reid Magney | Jan 2 13
2 Answers

Selecting correct windows

I am currently planning a new cabin at Shaver Lake California with elevation of about 5000 feet . The winter time low temp can get down to 10 degrees with Dec. and Jan. average low of about 21 degrees and daytime summer high average of about 87 degrees. My question is this. Should I consider triple pane windows with SHGC of 40 to 50 for winter time warmth?
I currently live in the San Joaquin Valley where we typically use windows with the lowest SHGC we can find and just accept whatever U-factor the specific window type and manufacturer provides.

Thank you
Gary Richardson

In Energy efficiency and durability | Asked By Gary Richardson | Jan 2 13
4 Answers

Questions on heating upper floor and controlling indoor humidity

We just bought a house in Seattle (2000 sq ft. 2 floors + basement) that has an integrated water/forced air heat ducted system on the main floors and basement and convectair wall heaters on the upper floors. We are looking at improving our energy efficiency and also controlling humidity issues we are having (in the 55-60% range on the 2nd floor and basement)

We just had an energy audit done and our contractor recommended the following:

- attic insulation and seal

In Energy efficiency and durability | Asked By Stephen Lim | Dec 31 12
4 Answers

Stone wool versus blown-in cellulose insulation in double wall assembly

I am designing a wall assembly for a home in a very cold climate Zone 7. Considering labor and material costs, what is the most cost effective insulation providing me with the highest thermal resistance? I like the fire resistance of Roxul stone wool batts and the idea that it's more DIY. How about the air transference between the two products? Thanks.

In Energy efficiency and durability | Asked By Matthew Michaud | Dec 30 12
Register for a free account and join the conversation


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