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!


4 Answers

Frost on outside of triple pane window

Every so often I notice frost/water (depending on outside temp) developing on the outside pane of my triple pane windows. It's infrequent but will mostly notice it early mornings. Actually, as I sit here this evening (68F indoors, 28F outdoors) the exterior of my windows are frosting up a bit. Interior pane is warm to touch. No moisture problems inside. Air exchange keeps interior moisture around 35-40% in the winter. Moisture (minimal-in bottom corners) only forms on interior windows when it's -10F and below. Thoughts? Thanks.

Asked By Matthew Michaud | Nov 28 16
7 Answers

New earth sheltered PAHS construction

I would like all opinions regarding my new home construction project. I have a full 3 days experience learning Sketchup and have managed to put several ideas on paper. Please review my plans...and pick holes in them :). I don't guarantee to change my mind, but I do promise to research varying opinions thoroughly and supporting data would be appreciated.

Assumptions:
Mixed humid climate Missouri 39 deg latititude
CoMo HDD 5173
CDD 396
Sunny days 195
Humidity ave 70% 83% AM, 56% PM
111 days rain for 46"/yr
10 days snow for 14"/yr

Asked By Laurel Davison | Nov 28 16
6 Answers

Insulating a cathedral ceiling

Martin,
What is the most economical way to insulate an 8/12 cathedral with 2x6 rafters, 1x4 "sheathing" with 4" gaps, no barrier...you can see the underside of the metal roofing? The roof is in good shape so I don't want to remove it. I can fir the rafters and vent if necessary but would rather not vent unless necessary. I plan on installing a wood celing without drywall. The house is in Charlottesville Va which is mixed humid. Sorry if you already answered this but I couldnt get back to the other place I asked it.

Thanks, Richard

Asked By Richard Uhler | Nov 28 16
1 Answer

Can unfaced polyiso be used for radiant heat systems?

I have radiant tubing installed between floor joists. I've placed a foil reflective sheet beneath the tubing and though faced fiberglass insulation is recommended to be placed beneath the foil sheet, I want to use un-faced polyiso boards 3" thick instead. The boards will be exposed to a heated, block wall, basement that is reasonably dry.
I would appreciate your comments.
Regards, JTO

Asked By John Oliver | Nov 28 16
6 Answers

Insulating I-joists in a garage ceiling

Hello. I have been doing some research to insulate a 2 car attached garage with a room on top. Size is approximately 27x27, new construction. This is in zone-6, Augusta Maine region, and code is R30 for floors.

Asked By Tony Bouchard | Nov 25 16
6 Answers

I would like to know how install baffles around the rafters of hip roof portion of the roof.

I'm doing quite a few projects in my attic but have run into some snags and figured I'm reading so many articles on GBA, I might as well ask a question here. I'm breaking my questions into parts below and any assistance is appreciated. Before posting here, I did read quite a few forums on GBA about these topics and on other websites. Thanks for any help you can provide!

1) Insulation Baffles

Asked By Josh Z | Nov 27 16
2 Answers

Methods for keeping cellulose insulation from gas flue line

Hi,
I am preparing for an attic project: air sealing, and blowing in new insulation.

We have a gas furnace, and its exhaust flows in a Type B vent pipe through the attic and out the roof. The Type B requires 1" clearance to combustibles.

There is already metal around the vent pipe where it enters the attic (picture should be attached). There is some gap between the vent and the metal, which I plan to seal using high temperature caulk.

Asked By Sam Smith | Nov 27 16
7 Answers

Domestic hot water heat recovery: Two systems or one?

We have a large footprint house with multiple bathrooms. The Power-Pipe product seems to be an excellent way of recovering shower waste heat. The question is how to deal with multiple bathrooms that are more than 20 feet apart in a 3 story house. A central drain would be an easy otion and allow the use of one power pipe BUT the hot water woudl need to traverse a great deal of PVC pipe before getting to the power-pipe. It would also be complicated to plu,b to feed from the power pipe to to the mulitple showers drawing from it (in order to plumb the cold side of each).

Asked By Edward Cambridge | Nov 25 16
2 Answers

Whether or not to insulate open joist bays between 1st and 2nd floors .

So far Erik North’s Free Energy Maine blog/website has been the only site that actually answers the question about whether or not to insulate open joist bays between 1st and 2nd floors on his blog post “Should I Insulate Between Floors?”. I tried posting a comment on the blog page looking to get his suggestions what is the way best resolve this issue, but it doesn’t go through.

His site led me to the Green Building Advisor webpage, so I am hoping that someone here would be able to provide me with some helpful advice.

Asked By susan deissleider | Nov 26 16
9 Answers

Ductless HVAC and humidity control?

We live in Pensacola, Florida and area with extremely high humidity. We are building a new house which is about 2800 sq ft. House consists of a main floor at about 1800 sq ft, second floor at about 800 sq ft and a loft at about 200 sq ft. The current plan is to go with an all ductless Mitsubishi HVAC system, well actually 2 systems. 1 controlling the first floor and a 2nd for the 2nd floor and loft. We have a very competent local installer and I have zero doubts about their capabilities and the pricing I feel is fair.

Asked By Thomas Roberts | Nov 27 16
Register for a free account and join the conversation


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