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!


22 Answers

Need sizing advice on a minisplit unit

I installed a Mitsubishi FH12NA in summer of 2014 when they first came out. I live in inland San Diego, and it can get hot, like 10-15 degrees hotter than the coast.

My condo is a studio and is only 420 sq ft. I'm on the upper unit of 2 stories. I face East and South. I have a skylight and dual-pane windows. Building is 1978 construction.

My Mitsubishi is weak. I set the temp and it will barely do anything. I have to set the temp to 61 and manually put the fan on high for it to do anything. Even "powerful" mode is weak.

Asked By aypues | Mar 16 17
0 Answers

Cape Cod Attic Cellulose Machine

My finished attic in my cape cod has terrible temperature regulation up here in central Maine. So far I've put 1 inch foam between the floor joists sealed the gap with foam. I've also spent days air ceiling the upper attic. Next step is for me to dense pack the sloped ceiling, which is made up of 2x8 rafters. I'll be using accuvent cathedral ceiling extensions to provide ventilation. The sloped ceiling is about 5.5 feet long so I'll be connecting two of the vents together and stapling at either side. The house is about 34 feet long and I have slopes on either side.

Asked By scifijock | Apr 25 17
4 Answers

Housewrap under rigid foam AND taped rigid foam at windows

the set up: Climate Zone 3. I'm using a standard house wrap between the OSB sheathing and the 1" rigid foam. The rigid foam will have all seams taped and will act as the primary WRB behind 3/4" vertical furring and lap siding. The Question : How do I terminate the house wrap at windows? just bring all the way into the "outtie" window bucks (caulk to buck), install rigid foam, then install window peel and stick flashing on bottom/part way up the sides. Install window. Would you recommend a 2nd layer of house wrap around the windows? Attached to the rigid foam?

Asked By Inger Peters | Apr 17 17
1 Answer

Insulating a corrugated metal floor deck

Hi -

I have a garage on a sloped waterfront lot in zone 6a (lots of moisture). The cement garage floor was poured on top of a corrugated metal floor deck held up with steel I beams. Under the main garage floor is a decent space that I'd like to finish and heat (unsure if I'll ever heat the rest of the garage). Spray foaming the underside is one option I would assume but its costly. Would polyiso foil faced boards be an option if the seams were well taped or foamed?

Very much appreciate this forum and any feedback!

Asked By P Stone | Apr 25 17
3 Answers

1974 construction retrofit

A friend is looking to replace siding and windows on his 1974 house in climate 4 marine. The main floor and upstairs walls are 2x4 and the basement walls are 2x6. There is timber framing inside that I suspect bridges to the ext sheathing w/o any insulation. Where he has removed some of the vinyl siding, he found fiberboard sheathing (R1.32 stamped on it). I don't know what is under that. (The garage is just studs + fiberboard + siding). The gable walls have 3" overhangs and the roofing is 2 years old.

Asked By Mark Walker | Apr 25 17
1 Answer

Will pocket door gaps at jamb allow avoiding a transfer duct?

Hi there: I'm trying to calculate undercuts necessary for balancing an HVAC system in a couple new residences. But then it occurred to me, that since all the doors are pocket doors, and since the Johnson Hardware we're using specifies a 3/16" gap between the jambs and the door panel on either side of the door, that this gap could be considered a "transfer grille" of sorts... The smallest 30x80" door would therefore have the equivalent of 20in2, not including any undercut.

Am I thinking about this in the right way? Do these 3/16" gaps give me what I'm assuming they do, in terms of airflow?

Asked By jonathan nagar | Apr 25 17
14 Answers

Raycore - is it the product for me?

I was pretty much on board with buying Raycore for the 4500 s.f. home I am building in downstate NY, which is steel framed, so I actually don't need any structural value out of the exterior walls other than for supporting the windows and doors (and supporting the walls themselves). I am also going with a wire lathe and stucco on the exterior - Raycore told me I could direct apply the wire lathe and did not have to use any sheathing if I did not need the shear strength, but I am hesitant to do so.

Asked By Joe McCarthy | Jul 14 14
10 Answers

All-electric vs. natural gas in Zone 2

I'm building a house in Houston, Texas. It will probably be a 'pretty good' house - dense pack cellulose and exterior rigid foam installation with an encapsulated attic and targeting an ACH50 of <3 with an ERV system for ventilation. I will have a sizeable solar PV array on the roof - 6-8 kw so I have been debating whether to use natural gas as in my current house for multiple appliances or go all electric. Pros and Cons as I see them are:

Benefits all electric:
No standing monthly charge of $25 for gas since consumption is below threshold 9 months of year

Asked By user-6822325 | Apr 22 17
3 Answers

Roof rafter insulation plan

Hello,

Asked By Dean Tyler | Apr 25 17
4 Answers

Deep blown in cellulose for attic - questions

I have a few questions regarding deep (beyond R60) blown in cellulose for an attic. Cellulose is relatively cheap and I'd like to maximise my attic insulation without causing any other issues:

1. Several manufacturers of cellulose insulation have depth/R-value charts that stop at R60. Is there any practical reason for this, or is it just because most people don't bother going above R60?

2. Does compression above a certain depth negatively affect the performance of the insulation in any way? I.E. does your R-value/$ go down appreciably beyond a certain depth?

Asked By Lance Peters | Apr 24 17
Register for a free account and join the conversation


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