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!

0 Answers

Insulating block walls

I am currently remodeling an old gas station. The exterior walls are cinder block. The building is 26 feet by 48 feet with 12 foot high walls. One third of the building (26 feel by 16 feet) will be used for a meeting area and have two bathrooms. All of these walls have been framed up with dimensional lumber. The perimeter walls of this space have been insulated and a vapor barrier applied followed by drywall. The remainder of the building will be used as a heated storage area with no interior insulation. The exterior of the building is to have LP smart siding.

Asked By man of steele | Mar 20 18
1 Answer

slumping of siding from nailing through rigid foam

Thanks for any assistance you can provide.

I am wanting to add additional insulation on the outside of our home. We are in zone 6. Our current walls are 2x6, 24 inch on center with 6 inches of fiberglass insulation, 7/16th OSB with tyvek. We have lived with cedar siding for 30 years and are now wanting to remove the siding and windows. Replace the windows and us LP siding.

Asked By user-7005676 | Mar 20 18
2 Answers

Outdoor mini split condenser unit in an insulated ventilated box indoors?

I need to cool (summer) and heat (winter) one room which is total 16.7 x 12.2 x 8.5 feet (1731 cubicfeet) (5.10m x 3.70m x 2.6m). I would need a unit between 2 or 3 tons.

Unfortunately I am not able to install the outside condenser unit outside of the building. That is the reason why I need expert advice.

Asked By purpleAnt | Mar 20 18
13 Answers

To Spray foam or not?

I am trying to decide whether to spray foam my house which is currently down to the studs. I am in climate zone 2 so it is hot and humid most of the year. The house currently was built to have a vented attic. The house is about 3,000 square feet and is one story. I have a asphalt roof shingles that I had installed last summer. My HVAC equipment and water heater are in a mechanical room separated from the living space by walls and with a louvered door to the outside.

Asked By Kasey Doggett | Mar 18 18
0 Answers

Brick Ledge help with Rigid Foam Over CMU


I am doing a custom new construction home and am trying to get some economical ideas on how to best provide a brick ledge when I add up to 4" of exterior rigid foam in zone 5.

Currently, the plan is to have a 10 inch CMU basement, that then steps down to 6 inch CMU for 2x6 stud walls, the other 4 inches is to be used for brick that starts just below grade. The brick travels through the first floor. The second floor will be vinyl double lap siding.

Asked By Wayne321 | Mar 20 18
0 Answers

What is the minimum depth a water line must be in zone 6 and pure medium to course sand?

I know there must be code requirements but there must also be some scientific way to know at what minimum depths a well water line will not freeze, because I'm thinking the soil composition would be a significant factor. I am in zone 6 in Traverse City, Michigan in pure medium to course sand and on a hill 35 feet above a small lake. The sand is very dry.

Also, can I use Pex underground from the well to the house? I have heard that it is somewhat flexible and resistant to cracking or bursting if the water freezes.

Asked By user-6992381 | Mar 20 18
26 Answers

Insulate this!

This one-room addition has no foundation. There is insulated in walls (likely R11) and ceiling (likely R19 - certainly no more), but not in the floor. As you can see, outdoor air can simply pass through the open space under the floor. When the flat EPDM roof needs to be replaced in 5-10 years, we will install exterior foam board outside the roof deck. Heating is primarily warmed air from rest of house or propane fireplace. Cooling is AC from rest of house.

I'm considering digging 2' out under the floor, and sealing the underside with foam. What approach would you take?

Asked By Emerson | Dec 21 17
0 Answers

ERV with HEPA filtration options

Hi Everyone,

Been a lurker here and I have a question and looking for advice.

Im building a new home, my previous home burned down. Im in Southern California, climate zone 3b, and my house will be pretty air tight, built with sip panels and using mini splits for heating and cooling. House is around 4300 sqft, I talked with some people and they recommended 3 Panasonic FV-04VE1 ERV units for ventilation throughout because of the lack of attic spaces and expenses.

Asked By m4tr1x | Mar 20 18
3 Answers

What do you reccomend for slab edge insulation protection?

Every detail I have seen shows a protective layer but fails to say what has been used succesfully. I have thought of IRMA insulation but it is pricy and not readily available for the homebuilder. It would seem that something made for that purose should be available at a reasonable cost.

Asked By Bob Bourguignon | Sep 14 10
2 Answers

Thermax over XPS rim joist

I believe the answer is no, but no problem layering foil faced polyiso over XPS in the rim joist, correct?

The XPS was can spray-foamed in, no issue if there is a slight air gap between the layers, correct?

Lastly, should I airseal the thermax perimeter with additional spray foam?

I have leftover 3" thermax and only 2" of XPS in that area so I wager it's a worthwhile application.

Thank you.

Asked By Justin Brown | Mar 16 18
Register for a free account and join the conversation

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