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

How best to insulate newly built garage with flat roof

Hi,

I live in Chicago (city of), Zone 5, and I have a new detached 2 car garage 20x20x11. The construction is wood frame with metal siding, drywall finished on the inside. I'd like to heat this garage to 50F during the winters in a cost effective manner (both insulation cost and energy cost), but I also want to do this right and not cut corners. I plan to heat this garage with a small ceiling mounted gas heater, like a Reznor unit.

In Energy efficiency and durability | Asked By Brian CL | Jan 22 13
5 Answers

Blowing dense-packed cellulose into Larsen truss walls and open rafter bays

This is what is keeping me up at nights:

Larsen trusses have no stud cavity walls and in my building the trusses are also open to the rafter bays (i.e no top plates).

I assume it’s the resistance to the blow by the walls and plates of the cavity which enable the density. I will be blowing cellulose into spaces with no boundaries so how to do I get the density and how do I know I have reached it?

Is it all about feel (i.e. resistence to the hose) and sound (i.e. back pressure while blowing)?

In General questions | Asked By Oak Orchard | Jan 21 13
3 Answers

Triple-glazed fiberglass windows - Zone 5A

What options exist presently for affordable triple-glazed fiberglass windows in New England? I like the wood interior of Integrity, but wonder if anybody has found windows that hit a sweet spot of performance, price, reliable customer service. Until recently, I'd been considering Intus windows, but ultimately don't want PVC or unpaintable, white interior sash and frames. Thanks!

In Green products and materials | Asked By John Rockwell | Jan 18 13
1 Answer

Bathroom ventilation

This is a followup on a question by Jim Blodgett on 7/5/2009 titled Bathroom/Laundry Ventilation through HRV. If I understood the responses to that question, a HRV can exhaust a full bath without separate ventilation through the roof or wall. There was some reference to boosting the exhaust into the HRV with a fan while showering. This in addition to the boost to maximum of the entire HRV by a wall control.

In Mechanicals | Asked By tom ruben | Jan 21 13
7 Answers

Why are bath fan dampers so lousy??

I just installed a couple of Panasonic WhisperGreen bath fans on a job, and before nailing them in I took a close look at the internal backdraft damper. I had two different types on the job... one had a curved plastic damper like a potato chip, the other had a flat piece of thin aluminum, which I am used to seeing. Both types had a gap all the way around the perimeter... not a large gap, but there was no foam seal there, and I'm sure these will let in a lot of outside air during the blower door test, as well as during some windy conditions.

In Green products and materials | Asked By David Meiland | Jun 17 11
8 Answers

Vapor Barrier to Prevent off gassing of CCA treated wood and OSB ?

I am in the middle of house building for a passive solar designed house in a mild marine Climate in southern Chile ( similar to Portland Oregon) where likely using a vapor barrier would not cause problems from what I understand.

The house frame upper and lower floor was built with OSB which I understand contains formaldehyde and CCA pressure treated wood. These are common construction methods where I live.

In this case might someone recommend a vapor barrier to prevent off-gassing from the CCA wood and formaldehyde in the OSB ?

In General questions | Asked By marion marshall | Jan 19 13
4 Answers

Wall assembly strategy using Dow structural insulated sheathing

I live in MD, climate zone 4 and want to use the DOW SIS 1" with blown in high density insulation. I can use a 2x4 wall to achieve R20 in the wall. Please help me settle a disagreement with my architect. He is concerned with using the DOW SIS product because the product has such a low perm rating that it will act as a vapor barrier and the wall won't dry to the exterior. He has traditionally used an interior poly so the wall needs to dry to the exterior. I say leave off the interior poly so the wall dries to interior.

In Energy efficiency and durability | Asked By Ryan Sober | Jan 19 13
1 Answer

Basement insulation retrofit - walls versus floors

Here and elsewhere its commonly advised to insulate basement walls with foam panels and permeable walls. My understanding is that this allows water vapor to diffuse through insulation and wall assembly without the occurrence of condensation and related problems. I've not seen where installation of a vapor barrier between wall and foam board, whether plastic sheeting or waterproofing agents is recommended, at least not unless liquid water was entering through the walls.

In Green building techniques | Asked By Andrew Alden | Jan 19 13
26 Answers

What should I do about improper installation of an air exchanger?

A year and 4 days ago, we moved into a brand new house. Installed already was a Venmar AVS air exchanger. Immediately we found that the house always felt cold. Being a newly constructed house, and our first winter in the house, we thought that we just needed to 'let the house warm up' and remove the humidity. We left the air exchanger on the setting that was recommended by the installer. We found that the house, and basement especially always felt cold. The windows constantly have condensation on them, and it is difficult to breathe.

In General questions | Asked By C Wat | Jan 17 13
4 Answers

Achieving net zero in a row home with one minisplit per floor?

I would like some opinions from all you smart people.

I have read many of the articles/posts on this site about a one head per floor minisplit approach for a net zero buildings. I do gut renovations of row homes in DC and have LEED Platinum certification on some, but have not achieved net zero. But I really want to!

Since these are existing ~100 year young brick rowhomes, mostly with attached frame porches, we cannot achieve a passive house tightness with our current construction techniques. We achieve in the neighborhood of 3.5 ACH50.

In Mechanicals | Asked By Tanya Topolewski | Jan 18 13
Register for a free account and join the conversation


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