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!

2 Answers

Are polyisocyanurate materials considered vapor barriers and to be avoided for insulating basements?

I live in Central Minnesota. Our home was newly built roughly 3 years ago. It was not insulated on the exterior, but foil-faced DOW Thermax Sheathing was installed on the entire basement interior. This has a permeability rating of 0.03. This is basically an impermeable material. If we want to avoid moisture problems when finishing our basement, do we need to take this down and put up something with more permeability like EPS? We do try keep the humidity below 50 or 55 degrees in the basement.

Asked By Andrea Zimpelmann | Jan 15 17
1 Answer

Minisplit troubleshooting


I built a well-insulated house this fall and after learning about minisplits on this site, we decided to heat our house with 3 minisplits. I can write more about this at a future date, but for now I'm having trouble with one of them and am trying to debug it to get as much information as I can before approaching the HVAC tech that installed it. We are in climate zone 7, so we have a lot of cold nights here (we've been below -22F several times this winter).

2 of our minisplits are Fujitsu 15RLS3H, which have been working just fine, no problem heating our house.

Asked By Nick Hall | Jan 23 17
0 Answers

HVAC conundrum

Hi all,

Asked By Will Bowling | Jan 23 17
5 Answers

Mini-split v Package Unit Humidity Control; Sizing and Configuration

I have a 1920's house in Tallahassee, Florida - 2x4 frame construction with shiplap siding, no vapor barrier or insulation except in the attic and one wall that was installed later (originally a screened in porch), and a fair number of windows. I have sealed the floor and walls of the dirt crawlspace using heavy plastic with vapor-barrier tape at the seams, but there is still appreciable air flow between the foundation wall and the girders. The main floor is ~1,600 sq. ft.; approximately ~600 sq. ft. of the attic has been finished into a bedroom and bath.

Asked By Ellery Sedgwick | Jan 20 17
41 Answers

Domestic hot water and space heating

I am trying to put together a system that can deliver domestic hot water and heat the house. The colonial house is in Brooklyn, NY ( zone 7), 29' x 33' and consists of 2 floors + basement. I am doing complete renovation and already removed all walls throughout the house and will use closed cell foam insulation in all walls and roof. I plan to run Pex in joists for both floors and I am thinking of using baseboard in the basement.

My questions are:

Asked By Vladimir Polyakov | Nov 3 16
6 Answers

Basement Insulation Question


I'm building a house in Zone 5 (southern CT). The house will have a full basement with spray on waterproofing. There is no sub-slab foam. The builder budgeted for 2" of XPS (with dimpled moisture facing) on the sub-grade exterior of the foundation walls, but NOT the above grade portions. There will be a footing drain running to daylight and a shed water system to catch storm water running off of our house (2 foot overhangs; no gutters). The soil is sandy loam and drains well.

Asked By Adam S | Jan 20 17
16 Answers

Insulating a new construction home

building a New home and doing research on insulation options. There is so many options on exterior insulation my head Is spinning. We are leaning on this idea and would like to know if it is a good idea or not?
2x4 walls sprayed with 3 inches closed cell foam
tyvek drainwrap
1 1/2 inch xps
We live in Michigan zone 5
Will this work or is a moisture issue? I've read articles with different opinions it's all confusing.

Asked By Colleen A | Jan 22 17
3 Answers

I am having a house built and have some questions about the crawl space.

This is a northern Idaho climate and the house was designed to be at garden level. There is a crawl space and the floor joists were originally designed to be hung with Simpson hangers below grade. Instead, there was a short support wall placed on the footings and the floor joists are sitting on the short wall. We intend on making the crawl space conditioned/mechanically ventilated. The short wall was installed within 1/8 of an inch of the foundation wall.

Asked By justin edwards | Jan 21 17
6 Answers

Vapor Barrier on top of SIP floor?

We are working out the details for the construction of our new house in the Pacific Northwest. Our architect and structural engineer have specified a 9 1/4" SIP floor for the 1st floor. Since we will be building in a flood zone, our foundation will be an open design with concrete columns extending from a mat foundation. Horizontal beams will sit on top of the columns and the SIP panels will sit on top of the beams. The structural engineer has specified a factory treatment of "bluewood" preservative to the bottom face of the SIP panels.

Asked By Kevin Camfield | Jan 17 17
6 Answers

How to insulate a vaulted ceiling

I am an American living in Provence France. We have hot summers and for the most part mild winters. In January, temperature can drop into the upper twenty during the night. It is a dry climate. I have been renovating a house at different times since last April. During the spring of the year I did the outside roof structure. I installed a new wood decking then a product called flexotuille designed to put under a clay tile roof. After a few other project, I have removed the inside ceiling in the den area in order to vault the ceiling in this area.

Asked By Louis Mattei | Jan 23 17
Register for a free account and join the conversation

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