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

Q & A Instructions

[Click map to enlarge]

drawing of climate zone map.gif

Advice can depend on climate — Please specify your climate zone in your question.

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!

Ask a Question >

3 Answers

Site-built windows / direct glazing recomendations

Hi,

I'm in the process of building a new construction residential home in climate zone 5 at 6000ft - Boulder, CO. With conditioned floor area at about 3500sqft, I need to install 20 or so fixed picture windows approx 4'x6' on the south side of the house (mainly greatroom/dining room).

Design wind load is 131mph and over all air infiltration rates of <3ACH50 need to be achieved.

The building department does NOT allow 100% vinyl windows - they need to be fiberglass/wood/aluminum/fibrex with U factor <0.30. Site built windows are allowed but this is where it gets complicated.

Asked By Bernard Lam | Sep 27 16
59 Answers

Mooney floor

I want to put insulation on top of a concrete floor.
A layer of foam + plywood bolted to the concrete has been suggested. (By Dana I think)
While that looks an good option I've been exploring more low cost options.

What about a Mooney wall, flooring variation.
Thinking about 2x4 + 2x4, filled with blown in cellulose. Likely GreenFiber or InsulMax.

Is that a good alternative?

Asked By Tony Tibbar | Aug 6 16
5 Answers

How to encapsulate a brick veneer crawl space

I am in the process of encapsulating our crawlspace and have a few questions. The house rests on concrete block piers and contains a brick veneer that covers the crawl space and extends below grade. There is a 2-3 inch air gap between the brick and the framing as well as the concrete blocks. The house is located in Climate Zone 3A so plenty of humid air.

Thus far I've installed a 12 mil vapor barrier over the dirt floor and up the sides of the brick wall (leaving a 3 inch gap for termite inspection). I've also closed up and sealed the vents.

Asked By Nate Wofford | Sep 27 16
6 Answers

Please help me pick the best option for HVAC replacement

We moved into this 20 year old house here in Nashville, TN in June and have been doing various projects to bring the home up to and above current building best practices. We have put open cell foam in the attic (average ~8 inches with rafters covered) and have encapsulated and foamed the crawl with 1.5 in of closed cell and 12 mil vapor barrier. We replaced the upstairs HVAC with a new 5 ton Trane xr17 and S9v2 furnace.

Asked By John Sexton | Sep 8 16
3 Answers

Do I have an issue?

The weather is my part of Zone 3 is still pretty hot (90s during the day with a cooling trend into the upper 80s). I noticed that my two year old air-source heat pump is struggling a bit to keep things comfortable. The thermostat upstairs is set for 77 degrees but the temperature is hovering around 81.

I also observed some wetness under my outdoor unit as well as some similar signs of water in the pan under the air handler. What do you guys think? Am I low on refrigerant? What might cause that?

Asked By Steve Knapp | Sep 26 16
3 Answers

Can Tyvek be used over fiberglass insulation that is falling out from between the roof rafters?

My parent's 1975 cape on the Vineyard has an unfinished second floor in which there is one occasionally used bedroom which has been sheet rocked. The rest of the attic is simply exposed fiberglass insulation between the rafters. In some places the insulation is falling out. Can we use Tyvek stapled to the rafters to keep the fiberglass in between the rafters and out of the atmosphere ( exposed fiberglass insulation is an irritant). Technically we want to keep the "attic an unfinished attic".

If Tyvek is not appropriate can we use the pink resin building paper?

Asked By Ruth Cutler | Sep 27 16
15 Answers

How much are mini-splits really affected by altitude?

Hello -

I'm sizing a heat pump mini-split for my 20x20 garage, which has been pretty well air sealed and insulated with closed cell foam. I've had a series of installers out and the recommendations were all over the place, ranging from 12k to 18k BTU, and from $3k to $12k.

Two of the companies actually bothered to do a load calculation, and I tried it online as well - but those numbers had a broad range, too.

Asked By Dave H | Sep 22 16
2 Answers

Use poly with Roxul (on ceiling)?

Hello,
I am zone 4A, about 40 miles south of St Louis, Missouri. I am gutting my 1937 bungalow. It has two attic bedrooms (so it is a 1.5 story home), and it has an unvented attic. I want to leave it unvented, because of the multiple dormers. Eventually, the roof will be insulated with closed cell foam, but that will be a long ways off. I am not gutting the upstairs for quite a while. I have gutted the first floor and insulated the walls with Roxul R15 rock wool. I just ordered Roxul R30 to put in the first floor ceilings.

Asked By Lonnie Sullivan | Sep 26 16
17 Answers

Quest for EPS

Finding extremely limited offering of eps rigid insulation in my region (upstate ny, north of Utica).
In my manufacturer search I found a product made by Cellofoam called Polyshield. They describe it as a sheathing product and it's eps with polymeric facers on both sides added for strength.
Is anyone familiar with this product?

Asked By Daniel F. Vellone | Sep 20 16
3 Answers

Does anyone use the wifi controllers on their mini splits?

Hi all,

I am a bit of a gadget geek (in addition to starting to become an energy nerd). I like dabbling in technology and home automation.

At our old house, I had a nest thermostat controlling a typical 2-stage furnace and a/c unit. I really enjoyed the nest functionality... setting up schedules, tracking usage, turning things off/on while on the road. Also, we lived in an inefficient house, and paid a lot for heating and cooling, so I was always looking for ways to raise/lower temperatures when we were out or sleeping, or any other ways to adjust the usage.

Asked By Clay Whitenack | Sep 26 16
Register for a free account and join the conversation


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