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!

9 Answers

Is spray-foam worth the $23k extra cost?

Our new home is currently under construction in Toronto, Canada. I'm doing my best to take advantage of this opportunity to create energy efficiency where at all possible. We will have solar panels and hope to get a Tesla Powerwall when available.

However, in regards to insulation I'm unsure how to proceed:

In Energy efficiency and durability | Asked By bob banderson | Nov 6 15
6 Answers

Closed-cell spray foam in cathedral ceilings

Hi, I have a question about closed cell spray foam insulation in a cathedral ceiling application as follows:

In General questions | Asked By Mike Stoick | Nov 5 15
2 Answers

Water storage in conditioned crawl space

We are about to build a conditioned crawl space (IFCs,sub-slab EPS, with venting to single storey living space) and land two high-performance modular units on the foundation. Our drought-impacted southern Oregon property (4C) has limitations on construction of open ponds, but we are looking at using military water bladders for storage of water catchment from barn and house roofs. The house will include blown cellulose in 2x6 framing with 2" Agepan exterior insulation and Hardi-plank siding. We will blow the attic to R-60 and heat/cool with 2 mini-splits, each about 22,000 BTU.

In Green building techniques | Asked By ALAN Hart-McArthur | Nov 6 15
5 Answers

Strategies for internal rigid foam


First, thank you for all the great advice on this site and your willingness to help. This is a wonderful resource!

I have a brick on 4" cinder block wall that I am looking to insulate from the interior. I am 95% sold on polyiso vs XPS due to the higher R value and the fact that it is mounted on an interior wall and hopefully will not be subject to the reduced R value as temps drop. I have about 1.5" with which to work due to plumbing code (toilet to sidewall)

In General questions | Asked By G S | Nov 6 15
2 Answers

Rockwool insulation in air vents

I was at a home and we discovered that rock wool batts were lining the return vents. Does this pose any concern.

In General questions | Asked By Robert Hronek | Nov 6 15
5 Answers

Minisplit installer recommendations — Massachusetts

Can someone recommend a mini-split installer in MA? I have had six mini split installers (Fujitsu & Mitsubishi) look at my house and each and everyone either wants a head in every room or wants to install supplemental heat in every room. The house was built using the PGH concept but it seems the installers I've come across have no experience in designing a system for one. They all feel that you need heat in every room no matter the load. Thanks!


In Mechanicals | Asked By Arthur Ledoux | Nov 3 15
5 Answers

What is a good R-factor estimate for a wall assembly with old UFFI foam from the 1970s?

I'm doing some modeling to guide a DER of a 1900's house. Bore-and-fill urea/formaldehyde insulation was added in the 70's. It's shrunk a bit and is quite fragile as expected. I'm looking for a realistic R value to use for this assembly. The wall is 2x4, plaster and lathe on the inside, 2 layers of siding on the outside. My guess is that the old foam has an R of 12 total (3" at R4 per inch). Any inputs on what R to use for this assembly?



In General questions | Asked By Tom Lange | Nov 5 15
2 Answers

Vapor barrior termination on mono slab?


I am building a small house in TN on a mono slab. My local building inspector strongly recommends not insulating the sides of slabs due to termites in my area. So, my question is where should I stop the vapor barrier? See attached pic. My initial thought was to stop at point C, but if there is any incorrect sloping I would think water could get trapped between points C and B. Should I stop it at point B?

I very much appreciate any thoughts on this.


In General questions | Asked By JOE ROBERTS | Nov 3 15
15 Answers

ERV vs. positive pressure vs. none

Leaky 1800's log home. Radon issue being worked on via traditional methods with mixed success. Radon issue improves dramatically when windows are open -- I assume this is dilution and perhaps also pressure equalization?

Wondering if ventilating may help dilute radon w/o the windows open energy penalty, especially in winter. If so:

1. Positive Pressure Ventilation -- perhaps a dehumidifier ducted to draw outside air -- might the positive pressure help reduce radon draw and simultaneously dilute the radon issue?

In Mechanicals | Asked By Andrew S | Nov 3 15
1 Answer

Spinning of washing machine

i have not choosen the spin mode while starting the washing machine after washing is completed,water has driven out while removing the door ,is spin is manadatory in front loaded washing machine,my brand is samsung front loaded machine please reply to my mail bhargavraj091@gmail.com

In General questions | Asked By Bhargav Pichika | Nov 5 15
Register for a free account and join the conversation

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