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!

3 Answers

Gree Mini-split heat pumps

I'm hoping Dana will weigh in on this question given his expertise with specifying and analyzing mini-split heat pumps.

There are some new heat pumps on the market from Gree that appear to approach the performance of the best units from Mitsubishi and Fujitsu. It appears to me that the cooling efficiency is right up there with Mitsubishi and Fujitsu, though the heating efficiency isn't as good. They do however specify heating capacity down to -20 degrees F.


Asked By Joshua van Tol | Oct 9 15
4 Answers

Insulating a crawlspace

Hi, I have a 70 yr old home built on a post and pad foundation. It is quite leaky and I'm in the earlier stages of fixing it up. I'm currently in the process of removing and replacing the skirting that runs the perimeter as it is unisulated and has enough rot to warrant its replacement. We live in southern coastal British Columbia. Winters here are rainy and only drop below freezing for short periods of time. My plan is to frame between the posts and fill with sheets of 2" xps topped with a rainscreen and cedar siding. The idea is to trap the heated air that escapes under the house.

Asked By Michael Blake | Oct 10 15
0 Answers

Dense pack cellulose in sloped ceilings -- need vent chutes?

I have an 1800's story and a half log home. There are knee walls on the 2nd story which have been insulated in a variety of different ways -- but most knee walls are treated as unconditioned space.

An insulation contractor proposed bringing the knee wall floors and the upper attic floors up to R50 by adding more blown in cellulose.

He proposed stuffing the rafter bays in the knee walls and dense packing the sloped bedroom ceilings (connecting the knee wall to the upper attic) with dense pack cellulose.

Asked By Andrew S | Oct 10 15
11 Answers

Moving a gas water heater into the envelope of the home...or switch to electric?

I just acquired a early 90's home and it turns out we can't get our minivans into the garage! On one side we have the HVAC equipment and on the other the water heater (both are gas). The HVAC I think we can relocate to an area of the bonus room directly over the garage so there will be minimal adjustment needed to the duct work. The logical place to relocate the water heater will be just inside on the same wall it is now which is currently a laundry room. I have never had a house with gas units inside the envelope of the home. So....

Asked By Andrew Bennett | Oct 9 15
4 Answers

Using nailbase panels as wall sheathing

I'm considering framing a large addition with 2x4 studs (actually, engineered studs) 24" OC with open cell spray foam in the cavity, with a exterior application of 2" nailbase (1 1/2" foam with OSB sheathing attached). My question is whether the nailbase will serve the lateral bracing function of typical sheathing, given that it will be separated by the 1 1/2" of foam to the studs. In other words, can I just use nailbase without adding a redundant layer of sheathing directly applied to the studs?

Asked By David Hornsteing | Oct 9 15
12 Answers

Below grade XPS placement, protection, and detailing

I'm pouring a traditional 8" concrete foundation for a client this week. They planned to have us place 2" of XPS foam on the outside of the walls for insulation. Once they can afford to finish the basement, they would place another 2" of foam on the inside of the walls between treated 2x2s and sheetrock over it for the finished assembly.

I've attached a rough sketch of the various components.

Asked By Nethaniel Ealy | Sep 16 15
3 Answers

Need help selecting MassSave cellulose densepack contractor

I know bunch of you are here from MA, so I figured I should ask here.
Contractor, that did insulation work on my house last year is no longer in MassSave program. One they recommended is booked literally into late spring and won't take on new bookings.

So now I need to find a contractor to pack my empty walls (clapboard siding). Any recommendation for solid contractor who can do the job in Waltham area? List is like 100 contractors long, so it is hard to pick.


Asked By Apollo S | Oct 7 15
2 Answers

MItsubishi or Fujitsu, dual or single

I am renovating an 800 sq/ft Shotgun style house. I have had icenyne spray foam insulation sprayed throughout; ext. walls, attic, and crawlspace are all sealed. I am trying to decide what to do with hvac and am looking into mini splits. I prefer the ceiling cassette unit for looks. I am in the Louisville, KY area. The floor plan is mostly open with the living room/kitchen being one zone and the bathroom, bedrooms and utility room being separated with two doors.

Asked By Erich Popp | Oct 9 15
12 Answers

Mini-split + heat pump water heater OR geothermal cool/heat + water heating?

Dear All,
I have read a number of articles on this forum and most seem to favor ductless mini-splits over geothermal. I believe peopel have said performance may be neck and neck while up front costs probably favor the mini-split.

However, what happens when water heating enters the equation? Some background:

Asked By Gina Jasso | Oct 4 15
24 Answers

How is thermal bridging prevented?

The construction process of our home, in southeast Iowa, was completed in January 2014. The house has fiber cement lap board siding and an interior spray foam insulation. In March of 20014 we noticed moisture accumulating, in a vertical line pattern, on the east elevation of the house.

Asked By S. Schneider | Oct 5 15
Register for a free account and join the conversation

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