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

Manual J, D, S

I am working on a major remodel of my 1950s house. The existing ducts are metal. I am looking for someone who can advise me on whether my existing ducts are properly sized and who can perform a Manual J and S since I will be replacing the air conditioner and furnace. I am outside Houston. I would prefer a 3rd party consultant over an HVAC company. I see some companies perform this service without a site visit.

Do I need a local company who can come to the house or can they perform these calculations accurately without visiting my house based on the floorplan?

Asked By Kasey Doggett | Jul 25 17
9 Answers

Vented dryer depressurization and it's effects on radon levels?

Has anyone studied the effects on radon levels caused by running a dryer, or other unbalanced ventilation equipment, in a well sealed home?

Asked By Calum Wilde | Jul 24 17
0 Answers

Retrofit of a Cathedral Ceiling

I am living in a Log Home in Madison WI. (Zone 5-6) with a vaulted Ceiling. (2x6 rafters R-19) I am hoping to redo the roof soon. I wanted to put on a layer or two of Rigid Foam. XPS or EPS. Ideally getting close to R-20 plus the 2x6 insulated cavity. I will then put a standing metal seam roof on top of the foam using furring strips.

My issues are this. I am concerned that I will be trapping moisture between the XPS or EPS and the Vapor retarder or Vapor Barrier that is most likely installed on the warm side of the house. Right behind the sheetrock and before the batt insulation.

Asked By user-6884681 | Jul 25 17
20 Answers

Need ventilation suggestions for remodeled office - it's too tight!

Hi all -

I've successfully converted my residential 20x20 garage into a beautiful office and photo/video studio. It's beautiful and I'm very happy except for one thing: lot's of off-gassing, VOCs, and chemical smell. I've had the windows open for most of the last year and still if I close them, the odors build up over a few hours. Air testing shows high levels of VOCs, and detectable formaldehyde - likely from the spray foam or polyspartic floor covering but hard to say.

Asked By Dave H | Jul 17 17
4 Answers

Indoor Humidity Levels - Magnitude of Risk and Solutions

I have some questions about the risk posed by humidity levels in my house and how best to address that risk. I have read lots of stuff on GBA regarding the humidity issue. Mostly I am looking for confirmation that I am on the right track. Sorry for the length of the following in advance.

Asked By Patrick McCombe | Jul 25 17
18 Answers

Insulation question and new construction.... thoughts?

New construction, we are doing a non-vented attic to keep our HVAC ductwork in a conditioned space with foam on the roof deck. Come to find out, we can put foam in all the walls vs using bibs for the same price which surprised me. This will make for a tight house and this brings the question in my mind "what type of mechanical ventilation"? House needs to breath and have a good exchange of air.

House is a 2 story and about 2700 sq ft. 2 HVAC units will be installed. Biggest concern is a good ventilation system..

Asked By Thomas Roberts | Jul 20 17
3 Answers

6" wide aluminum insect screen

Anybody have a good resource with fast shipping? I'm looking at having to cut it into 6" strips from a 24" wide roll unless someone saves me!

Asked By Inger Peters | Jul 19 17
1 Answer

Sheathing Air Barrier and Vented Roof Assembly

Sheathing air barriers and vented roof assemblies both sound like wonderful ideas and seem to have the blessing of many building professionals. Are they compatible with each other?

I want to build a cathedral ceiling insulated with cellulose. Some people say such a roof must be vented and carefully detailed with an interior air barrier. Others are building them unvented with sheathing air barriers and are publishing their methods. Do you agree with them in any way?

Asked By user-6882359 | Jul 24 17
6 Answers

Furring down from trusses

I just received the engineering for my truss system and see that where I want to fur the 5 in 12 scissor trusses down with a 2x6 (so that I can insulate the attic out to the ext. walls), the notes say, "This truss design requires that a minimum of ½" gypsum sheetrock be applied directly to the bottom chord."
Trusses NOT over the vaulted great room spec "rigid ceiling directly applied or 6-0-0 oc bracing." Bracing is allowed in lieu of rigid ceiling elsewhere in the house.

Asked By Mark Walker | Jul 24 17
2 Answers

Walls and floor for one piece shower?


I have a one piece shower I just bought and am going to install it myself. I have never done so and am looking for a guide or advice on the best practice to make sure:

1) No leaks or water damage
2) Shower is properly stabilized

My first question is what materiel I should be using for the framed in walls around the shower? Can it just be directly against my studs or should I put up some mold free plywood/material first?

Asked By MichaelBa | Jul 23 17
Register for a free account and join the conversation

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