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!

11 Answers

Minisplit - One indoor unit for two adjacent rooms?

Do any of the minisplit manufacturers offer a wall mounted indoor unit that will service two adjacent rooms? I'm considering a minisplit to replace the gas furnace and a/c in my 1300 sq. ft. single level home in zone 3A (mixed-humid). Without a shared indoor unit on the common wall between two bedrooms, I might need five indoor units. The multizone minisplits seem to jump from 4 to 8 zones and the price jumps too. I understand the technical problems with one wall unit serving two rooms, but have any of the manufacturers solved them.

In Mechanicals | Asked By Steve Robertson | Oct 23 14
101 Answers

Water - The Wonder and the Danger

We live on a watery planet. 70% of the earth's surface is water (the same percentage of water in our bodies). It is the font and sustainer of life (SETI looks for water on other planets as the sine qua non of life). So why have our modern "green" building practices turned it into a monster? And how can we stop fighting it and turn it back into an ally?

In Energy efficiency and durability | Asked By Robert Riversong | Nov 28 10
3 Answers

If I don't cool my home on summer, should I think like I'm in a cold climate when I design my wall assembly?

In regards to vapor difussion, in a mixed-humid climate, where no AC will be used in summer, should a Cold Climate wall assembly design work just fine?

In other words, does the special concerns we have to consider when designing a mixed-humid wall assembly, have to do with being able to work succesfully and withstand both heating and cooling seasons? What if I don't have a cooling season (No AC in my home), should I just use a cold-climate approach?

This is for Pucon, Chile, which has a climate like US's 4-C, or Marine.


In General questions | Asked By Jose Castro | Oct 28 14
4 Answers

Installing ductless minisplit over refrigerator

Building an 800sf 2 story house, main floor is 400sf open floor plan. Would there be any problems if I were to install the ductless mini split head above the refrigerator?

I was thinking of mounting it on the front of the soffit so it would be flush or slightly proud of the front of the fridge, allowing it to spread air down without hitting the fridge. It would also be further from the coils on the back of the fridge. I read that it should be 7-10" below the ceiling.

In Mechanicals | Asked By Tom Frisch | Oct 28 14
1 Answer

Rim joist thermal barrier

The rim joist in my unfinished basement is insulated with 3 inches of rigid polyiso along with one part spray foam to air seal around the edges. My understanding is that building code exempts up to 3 1/4 inches of spray foam in this area from the thermal barrier requirement, but that this exclusion does not apply to rigid foam boards.

In Building Code Questions | Asked By Michael Lee | Oct 27 14
2 Answers

I just received a sample of Tyvek Thermawrap external insulation in the mail

It's being promoted as a vapor permeable alternative to foam board external insulation but I'm feeling dubious about how the installation is supposed to work. Anyone have any experience with this material?

In General questions | Asked By James Morgan | Oct 27 14
4 Answers

Insulating a metal barn

I have read a lot about condensation problems when insulating metal barns, as well as your blogs on bubble wrap scams and subsequent commentary.

In Energy efficiency and durability | Asked By brian mccoy | Oct 27 14
7 Answers

Add R-14 Roxul between the garage attic and the house?

I am currently in the process of insulating my attached garage using Roxul R14 "ComfortBatts". I live in Winnipeg and from experience -- when I did this in my last house -- it can improve the temperature by 10-15 degrees Celsius in the winter, without any heating. (And that was with a non-insulated garage door; my new house has insulated garage doors!)

In Energy efficiency and durability | Asked By Mike Lucas | Oct 23 14
4 Answers

Insulating detached garage attic in central Florida

I'm about to start construction of a 30' x 30' concrete block detached garage in central Florida. I'm using attic trusses and plan to use a white raised seam steel roof. I was not planning in insulate the block walls. What is the best way to insulate the roof? I want to keep it a cool as reasonably possible - I might add a window or portable AC, if I have to, but will not run it often. Depending on the final use of the attic, I might even try to condition that space. I'm concerned about moisture buildup inside - wet cars could bring a lot of water in.

In Energy efficiency and durability | Asked By Kelly Lear | Oct 3 14
2 Answers

How to deal with a void (cricket space) above an unvented flat roof?

we're in the process of building a new house and originally had a non vented roof assembly detailed for the flat roof portion of the house where we had a single ply membrane over sloped rigid insulation over a vapor barrier over roof sheathing, with batt insulation placed tight against underside of roof sheathing.

In GBA Pro help | Asked By Rachel Kim | Oct 27 14
Register for a free account and join the conversation

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