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!

1 Answer

Another "How to insulate this old house" question

I am in Louisville, Ky; climate zone 4A. I have a 115 year old 1.5 story house with gambrel roof and have obtained a ton of detail from this site on how to insulate behind and under knee walls, etc. while maintaining a ventilation channel.

In Energy efficiency and durability | Asked By Jason Hartlage | Jun 22 15
4 Answers

Insulating the Interior of Poured Basement Walls

This picture is from building science.com and shows an ICF foundation with insulation under the slab. My question relates to the interior wall plane where the floor slab meets it. Does the code require that the slab make physical contact with the concrete wall? If it does, how do code officials deal with situations like this one with ICF foundations? I wanted to have a similar insulation setup on the interior with poured walls. Prior to pouring the floor I would lay rigid foam along the ground and up the wall - thermally isolating the slab.

In Building Code Questions | Asked By Brian W | Jun 21 15
17 Answers

Distance of exhaust fan wall cap from windows and soffit intake vent?

How close can a wall cap for a bathroom exhaust fan be from a soffit intake vent?
I'm trying to efficiently vent a 2nd story bathroom without sending the moist air right back into the attic and I don't have a lot of options as far as placement is concerned.

In General questions | Asked By Joseph Moore | Jun 1 15
2 Answers

Trade offs of closed-cell foam between roof rafters

Hi All,

In Green building techniques | Asked By William Duerr | Jun 20 15
8 Answers

Use PERSIST and put the WRB inboard of the sheathing OR use PUR nailbase panels and put the WRB outboard?

I'm insulating my house on the exterior - the design currently call for 9" of Neopor with the WRB against (Prosoco - spray/roll-on ) the sheathing. The Neopor is outboard of the sheathing. 9" is a lot - but gives me the R-40, without having to use any insulation on the interior. I'm getting a great price on the Neopor.

Just yesterday someone suggested PUR Nailbase panels instead of Neopor. PUR is a (polyurethane) panel, and would reduce the size of the overall wall thickness, is vapor impermeable, and fire resistant -higher embodied energy though .

In General questions | Asked By brad hardie | Jun 19 15
36 Answers

Wet basement OSB sheathing

I want to do my walk out basement over, but the area sitting on top of my foundation which is 6" studs with OSB sheathing gets cold. If I use batting insulation it drips wet, even with humidity at about 50.

It's new construction, I should mention.

In Energy efficiency and durability | Asked By Neil Cicciu | Feb 6 15
98 Answers

Unvented slanted roof with radiant cooling and NO polyurethane in 4C

We are in Everett WA, north of Seattle, right on the coast, zone 4C. I hope that our location will save us...
We have a low sloping steel, west facing roof. Double, 30 weight felt paper underneath to dampen rain noise. I presume 1/2" plywood sheathing. 2x12" rafters, 11" true depth.
We will install WarmBoard R (13/16" thick OSB with aluminum tracks) underneath the rafters for summer cooling and supplemental heating in winter.

In GBA Pro help | Asked By Jan Verschuren | Mar 11 15
7 Answers

Filling cinder block with pea gravel?

I am wanting to build a house on some land I bought in Florida. I plan on using cinder block for my outside walls covered with stucco. I want a very high r value. Can I fill the cinder bock with pea size gravel to give the wall a higher r value? What would be the positive and negative implications in doing this?

Thanks, Gregg Webster

In Green building techniques | Asked By Gregg Webster | Jun 15 15
7 Answers

Air source heat pump water heater in a small mechanical room

I am building a 2-unit addition to a duplex in Portland, OR, resulting in a 4-plex. The new units will be largely separate from the old, and will be built to PH-like standards (very tight air barrier, heavily insulated). With an eye toward economy, I am thinking for the 2 new residences to share a mechanical room. In this mechanical room would be water heater(s) for both new units, along with an HRV (likely Zehnder 550) serving both units.

Relevant plans and considerations:

In Mechanicals | Asked By jonathan nagar | Jun 15 15
3 Answers

Attic ventilation

Many people where I live have installed solar roof fans to help with their existing roof ridge vents...is this OK, can this cause problems for the roof or shingles ?

In General questions | Asked By Paul Osmer | Jun 18 15
Register for a free account and join the conversation

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