Q&A: A Forum for Green Building Experts and Beginners

[Click map to enlarge]

Please register for a free account or sign in to ask and answer green building questions.

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

Geothermal - Sizing Issues - 4 Ton or 5 Ton?

I live in Cincinnati, OH and I am zeroing in on purchasing a geothermal heat pump for my 5800 SF (conditioned) home. My home is all electric is currently heated by an 8 year old 4 ton air source heat pump with 15Kw electric backup. My issue is the two geothermal companies I have contacted to quote the job disagree on heating load of my home. Both companies did Manual J calculations, but are coming up with different numbers. One company has the heat load at 55k BTU -- says a 4 ton is the way to go. The other company has heat load at 68k BTU - says go with a 5 ton unit.

Asked By joel perrine | May 3 15
0 Answers

XPS or EPS for venting cathedral ceiling cavity.

I'm planning to create a vent space in a cathedral ceiling slope. Cavity will be 13". I am planning on making a "U" shaped channel out of rigid foam, putting that against bottom of roof deck then dense packing the cavity. It seems to me that EPS is a safer bet here because of its greater permeability over XPS. But XPS is easier to get and stronger. I am a little concerned about dp cellulose crushing 1" of XPS. My understanding is that XPS is rated at 1.1 perm @ 1 inch thick, while EPS is 5.5. Is the XPS still a pretty safe assembly?

Asked By Joseph Carry | May 4 15
0 Answers

Spray Foam wall and 2x6 framing. How to seal stud to stud area's

I spray foamed my entire house. Roof trusses, wall cavity and even the floor.

We're just getting ready to do electrical and mechanical rough in and the spray foam guys are going to come back and scrape any exposed foam off the face of the studs, and also seal the windows and stud-to-stud area.

What they are planning on doing is using acousti seal where 2 studs sit side-by-side and then put tuck tape over the acousti seal.

Asked By Mark Helmrich | May 4 15
0 Answers

Spray foam covers entire 2x4 on roof truss...bad?

I had my roof deck sprayed with spray foam (to the underside of the truss). My roof trusses were designed at 16" OC and constructed with 2x4's. They needed to spray 4" of foam to get the code requirement for insulated value, so they covered the 2x4's completely on the roof deck.

Now I'd never really looked at and or thought about it till after they were done...(should have had the trusses designed with 2x6's) but the 2x4's are fully encapsulated with foam. I'm worried they are going to rot because they can not breath. Is is not a big "no-no" to encapsulate wooden studs?

Asked By Mark Helmrich | May 4 15
6 Answers

Perforated metal used in Roxul rock board install?

I've read through this article and tried to contact /find contacts for the owners, but was unlucky. The link to their blog http://agreenhearth.com/ no longer works..


Asked By Lucyna de Barbaro | Apr 24 15
3 Answers

Thermal break and insulation for gas fireplace flue pipe

We are building a tight and well insulated home in WY. It gets very cold here. We are paying special attention to creating a thermal break and insulating all ductwork to the exterior. They installed a "one pipe" gas fireplace and the metal flue pipe comes straight from the outside with no thermal break. I am told that it must have one inch of air around it so we are not able to insulate the pipe. I had suggested stove pipe insulation which is fire proof but contractor says code does not allow anything.

Asked By John Culbertson | May 4 15
5 Answers

Design Temperature

Design Temperature

It seems like most systems are designed around maintaining comfort on the coldest day of year. This can mean that the heating system is specified for 60,000 BTU but your average BTU requirement is 12,000 BTU. The mismatch likely adds quite a bit to the price tag of the boiler or possibly necessitates a boiler instead of something more economical?

Why wouldn’t a secondary heating system that can add heat to cope with the few days of the year where the heat requirements are at their highest be a more economical design?

Asked By M G | Apr 29 15
1 Answer

How can I seal this space w/ moisture in mind?

Hi All,

I am working on renovating our second floor which includes putting in a master bathroom and gutting and redoing an existing 2nd floor bath. It is a 1952 cape with brick siding on concrete block. The masonry walls are completely uninsulated in most cases. I have taken advice from the GBA site while researching various issues associated with this project and figured this would be a good place to ask about this.

Asked By G S | May 2 15
3 Answers

Foam Insulation on attic floor?

I'm about to insulate my attic. I've read a lot about insulating the attic rafters with foam to create an unvented attic. I've read about laying down a think layer of loose fill on the attic floor in a vented attic. I'm having difficulty deciding between them. And now am wondering about a third option.

Asked By Jason Crawford | May 3 15
5 Answers

Skip the plywood, go right ot the Comfortboard IS

I live in central Vermont, heating zone 6, hoping to get a little bit of feedback on the wall system I have in mind for a 4 season workshop (barn), with small efficiency apartment on the second floor.

Asked By Blake Olson | May 2 15
Register for a free account and join the conversation

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