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!


6 Answers

Is a ductless minisplit appropriate for a house with primary wood heat?

Hello,
I am contemplating installing a ductless mini-split heater in our new build house in Southeast Alaska. The climate is of course very wet, with fairly cool summers and fairly mild winters with the occasional cold snap.
We heat primarily with wood. Is a mini-split heater an appropriate choice when the wood stove is expected to do 80% of the work of heating? We want an auxiliary heater that will simply limit how cold the house will get while we are away for a long day or a weekend (to 50 degrees or so), but will not run at all when the wood stove is going.

In Mechanicals | Asked By Justin Smith | Jul 23 15
32 Answers

More confused....open vs. closed spray foam for my climate zone

Hi,

I want to finish off my third floor. My house is in Richmond, VA - Climate Zone 4 - (right in the middle of the zone). House was built in 1993. The attic is walk up and rafter built with 2x8s. Here are some pics of the space:

In Energy efficiency and durability | Asked By Joe Watson | Jul 21 15
5 Answers

Insulation for condensation control changes from IRC 2009 to 2012

I'm building a small house in Portland Oregon, climate zone 4C marine (according to 2009 IRC). I have 2x12 rafters with blown cellulose, then a layer of taped plywood sheathing for air barrier, then 3" of XPS followed by another layer of ply and the roofing on top of that. Since the ceilings are vaulted, it's an unvented attic situation, so I'm worried about moisture. I've got R36 in the cellulose and R15 in the XPS.

In Building Code Questions | Asked By Tom Frisch | Jul 26 15
15 Answers

Proper way to detail bottom edge of rigid foam next to sill plate

I am going to be installing 2" of rigid foam over my OSB sheathing soon and I have two concerns. The current one is what is the most DIY friendly method to protect that bottom edge of foam that is under the siding, but next to the ground near the sill plate? I want to prevent bugs of course, but also keep moisture out too. I see videos of pros using aluminum flashing but they have fancy breaks and coils of it. Is there a DIY alternative? Local supply store would be Menards if there is a certain product to suggest. Thanks.

In Green products and materials | Asked By Nicholas C | Jul 25 15
4 Answers

How much more efficiently does a ductless mini-split perform below peak demand?

My Manual J load calculation for my the 960 sf house I'm building in central Arizona shows a heating load of 13,535 BTU and a cooling load of 11,860 BTU.

I'm debating between two ductless mini-splits:
Panasonic E12NKUA with inverter: 12,000 BTU Cooling 13,800 BTU Heating, 20 SEER 10.6 HSPF
Panasonic E18NKUA with inverter: 17,100 BTU Cooling 20,400 BTU Heating, 18 SEER 8.5 HSPF

In Mechanicals | Asked By Jeff Cooper | Jul 27 15
2 Answers

Flat roof insulation

Here is the Chicago area.
If I can't ventilate the flat roof, then what happens?
what if I am using the fiber insulation and radiant barrier together..?

In Energy efficiency and durability | Asked By Mansig Yoon | Jul 26 15
5 Answers

Closed-cell foam in a 65-year-old Cape Cod roof?

We recently removed all of the vinyl siding and homasote from our cape. We installed R15 fiberglass in the walls - there was not insulation previous to this, just homasote. In addition, we replaced all of the windows with double glazed argon gas filled low E windows.

In Energy efficiency and durability | Asked By Michael Boice | Jul 24 15
17 Answers

How do I get and keep air out of my geothermal loop?

We have a "closed loop" geothermal heating and cooling system. 97 wells 300 ft. deep. 4 story building. 36 water source heat pumps. 72 electric water pumps. 219 ball valves.
There is no way at the high point (attic over 4 story) to release air and no easy way to add water to displace the air. The contractor keeps trying with their big pump and tank trailers to purge the system by driving the air bubbles out through the basement. No surprise to me, having observed the bubbles in my bathtub travelling upward, this approach keeps failing.

In Mechanicals | Asked By Todd Conradson | Jul 1 15
1 Answer

Questions about Earthcraft

We are looking at Earthcraft as a green building certification process.

If you have experience with Earthcraft your comments, and suggestions will be appreciated.

We offer a guaranteed $100 electric bill already up to 2000 heated square feet, so we're already pretty good at energy efficiency.

We're hoping to learn the pros, cons, and suggestions of others before we engage with Earthcraft.

Thanks for your time.

Rod

In Green building techniques | Asked By Rod Moelleer | Jul 26 15
4 Answers

Using I-joists for Larsen truss web and building wrap for blown cellulose

I am building a 2 story house on the Kenai Peninsula of Alaska and I am planning on installing a Larsen Truss on the exterior of a 2 story 2x6 framed house sheathed with plywood. As an owner builder who is trying to balance time efficiency vs cost efficiency I am trying to think of ways to speed up and ease construction of the Larsen truss. I recently thought of using I joists for the Web. It seems like this could speed up construction significantly allowing for the building of the truss on the ground prior to installation.

In Green building techniques | Asked By Chris Walker | Jul 26 15
Register for a free account and join the conversation


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