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!

7 Answers

Does this plan for a vented over-roof make sense?

Hi all, first time asking a question but I’ve found this Q&A very helpful in the past. Thanks in advance for your help.

I’m planning to add a vented over-roof to my zone 6 northern NY house. It has three roof sections: two cathedral and one with an attic. I’ll be dense packing the cathedral ceilings with cellulose and spray foaming the attic before over-roofing, making all three roofs hot and roughly R-25+ before the over-roof. Here’s the thinking on the vented over-roof layers, from bottom up:

1) Decking
2) Air barrier membrane

In Plans Review | Asked By Jan Wellford | Oct 3 14
5 Answers

Does the Air Scrubber Plus need the fan on continuously to work properly?

I had the Air Scrubber Plus installed on my central unit. I understand the fan helps the product purify the air. I'm concerned the fan will burnout if it is on all the time. Can you tell me if I need to leave the fan on 24/7 to support the product? If do, will continuous blowing damage the fan?

In General questions | Asked By Ann Cobb | Oct 12 14
7 Answers

Outdoor catalytic wood stove: smoke reduction devices

Hi all,

We have an outdoor catalytic wood stove with an 8-inch pipe, and our neighbors want us to cut down the amount of smoke. It sometimes drifts over in their direction... We live in the Northeast US and it's starting to get cold around here!

We found this Catalytic Add-on Stove Damper online:


In Green products and materials | Asked By Alex Forbes | Oct 13 14
2 Answers

Bathroom venting concerns

I have a 2 story/2-unit balloon-frame building from 1929, plus a hip roof. The 1st and 2nd floor bathrooms are on top of each other on the back center of the building. Both have fans, but neither vent to the outside!! We have mold/moisture concerns in the back rooms of the house. No wonder.

Venting each fan has a separate issue.

In General questions | Asked By A. Bradford | Oct 12 14
6 Answers

How do I cost effectively insulate the ceilings of my detached garage?

I have a 22x22 detached garage with a 15x15 addition on the back (both gable roofs) that I'm turning into a shop. I live in Iowa and have run a gas line to it and have purchased a gas heater capable of heating. I would like to heat the garage at low heat and will crank it for shop time. Each space has 2x4 rafters, but no insulation, no ridge vent or other roof venting and only one of the two spaces allows free flowing air to enter the building through the rafters running beyond the building envelope as the 22x space has wood blocking.

In Energy efficiency and durability | Asked By Matt McDevitt | Oct 12 14
9 Answers

How can I attach a ledger to an outside brick wall for a deck?

How can I attach a ledger to an outside brick wall for a deck when foam is used on the outside of sheathing?

I have 3 inches of foam then a 1 nice air gap, and I need advice on how to attach the ledger.

In GBA Pro help | Asked By michael kasales | Oct 9 14
5 Answers

Truly "smart" thermostats and boiler controllers?

Well, my new boiler is in (a Lochinvar WHN-85, with a Lochinvar SIT 40 indirect water heater). As far as I can tell this early in the season it's working fine. But, I've been thinking about my thermostats and how they communicate with the boiler, and wondering if there might be a better way.

My old boiler was a standard dumb boiler. Each circulator was on if its thermostat was calling for heat, and the boiler was on (full blast) if a circulator was on and the water temp wasn't at the limit. True bang-bang control.

In Mechanicals | Asked By Daniel Griscom | Oct 11 14
13 Answers

Should my indirect hot water heater have a mixing valve?

I have a 2300 square foot colonial, built 1960 in Massachusetts (Zone 5A), with three zones of fin tube baseboard. There's a 75 gallon whirlpool tub which we almost never use; the two showers are fairly low-flow. Heat loss done by Comfort-Calc.net was 55,840. I use town water, which is very good quality (Quabbin reservoir). I've accepted a bid to replace my heating system with a Lochinvar WHN-85 boiler and SIT40 indirect water heater.

In Mechanicals | Asked By Daniel Griscom | Sep 15 14
1 Answer

#2 about noise from outside

my question below was answered about putting in new window. i already knew that. and i've already tal ked to landlord, they will do nothing. . aside from these two things, could you let me know if closed-cell 2" foam , or 2" acoustical tiles will help at all? just wondering what i can try in addiction to the things i have tried that are mentioned in my note below. thank you, cindy

In General questions | Asked By Cynthia Oeser | Oct 10 14
17 Answers

Correct way to use closed-cell insulation on a roof?

I'm rehabbing an old 3-story brick building in Pittsburgh. The roof is a flat roof but pitched from front to back. I got estimates to spray closed-cell on the underside of the roof and essentially encapsulate the structure. There is a 'space' between the 3rd-story ceiling and the roof, so if I drywall the 3rd-story ceiling, there would then be an air space above the drywall. I'm also planning on installing a new rubber roof. So I guess I have several questions:

1. Is applying closed-cell to create a barrier at the underside of the roof the correct way to go?

In Energy efficiency and durability | Asked By John Murphy | Oct 8 14
Register for a free account and join the conversation

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