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

All steel building venting for home

We have an all steel building that we are turning into a home. It currently has a steel roof with fiberglass insulation with a vapor barrier on the warm side, there is no space between the insulation and tin other than the rib gaps of the exterior tin (the walls are the same setup as well). We are going to frame it with wood studs and add rock wool insulation in between the purlins (and girts for the walls) then put our ceiling/wall covering up which will create a cathedral ceiling. My question is how do we vent the ceiling with this setup?

In Energy efficiency and durability | Asked By Victoria Victoria | Feb 12 16
4 Answers

3" and 4" PVC valves that release water but keep air from entering

Need two of these. Can't find them. I have emergency drains that come from my home appliances to daylight. They're allowing too much air infiltration, because they are open at the daylight ends. They are rarely used but necessary if an inside leak develops.

In Mechanicals | Asked By Andy Nels | Feb 12 16
4 Answers

Duct manifold for a stand-alone ERV

I'm trying to figure out the best way to install my ERV ductwork. I don't have a forced air system, so each supply or exhaust will have it's own duct. I have seen the typical trunk/branch method, but a manifold system seems easier. Does anyone have experience with building a manifold system for mechanical ventilation? I will have three exhaust ports and four fresh air ports. I've looked at the Zehnder systems and they look pretty slick, but I cannot afford the price. I am leaning toward Thermaflex ducts, which are high quality flexible ducts usually used in commercial applications. Thank you!

In Mechanicals | Asked By Adam Emter | Feb 9 16
37 Answers

To crawlspace or not to crawlspace?

We are a group of four builders in Quebec breaking ground on a new construction this summer. We’ve been arguing over the niggly details for three years as we try to cobble together the most common sense, super-efficient, affordable house possible. As we seem to be proving, the discussions on how to build can go on forever...

In General questions | Asked By William | Jan 20 16
3 Answers

Do I need to vent soffits in with an unvented roof assembly?

I have large 4 foot exterior soffits. I am spray foaming the inside of the roof, an unvented attic assembly. Do I still need to vent my exterior soffit overhangs? Do I need to worry about the air trapped in that cavity if I do not?

In General questions | Asked By dean sandbo | Feb 11 16
6 Answers

Roof clips

Our roof will be 12/12 pitch with 2x6 raifters,would it affect much if we changed to 2x8 to fit a little more insulation,also our roof deck is 7/16 osb taped with a 1.5-2 inch polyiso nailbase on top if that,do you think we need roof clips on the first layer of osb or need to change that to 5/8osb?
Thanks

In General questions | Asked By Quinton Bryant | Feb 11 16
19 Answers

Mitsubisi Heat Pump- heat and cool

I am building a 1 1/2 story barn/garage 36 X 34 with an open upstair 2nd floor. It will have 2" form in the walls and 3" sprayed form in the ceiling. Cement floor. not too many windows and 2 garage doors.

I don't need it heated like a home but just confortable when I work in the barn. I would like to keep it about 40 degrees in the winter when not in use and will rarely need it cool in the summer. I live in southern CT.

I've been looking at the high efficienty units around 24,000 BTU. I also need to be able to set the temperature low (about 40) when not in use.

In General questions | Asked By Fred Gabriele | Jan 31 16
1 Answer

Steel-sided, conventionally framed, closed-cell-foam-insulated home

I have been pondering building a low cost, high efficiency, low maintenance retirement home, and would like some input on my theoretical systems.

The structure would have conventionally framed, 2x6 walls, with no sheathing. In it's place, would be diagonally place structural supports(2" x 2") spaced at 24". In that 24" space would be 2" foam. The wall would than be strapped horizontally(2" x 2"), and spaced at 24" with foam in that space as well. The steel siding would then be installed, and attached to the horizontal strapping, and through to framing.

In Energy efficiency and durability | Asked By Maine Builder | Feb 11 16
16 Answers

Are holes in exterior plywood sheathing necessary?

We are building a new home on the west coast of BC. Our framer has placed large diameter holes in the exterior plywood sheathing saying this is necessary to meet code and allow the exterior to breathe. Our concern is that when other protective layers placed over the sheathing break down over time (plastic and tape and glue only last so long) we have a welcome entry point for water, rodents, carpenter ants ect. How does this practice fit into an 'airtight' home??
We are not builders but can't find anywhere noted that these holes are necessary. Thoughts, advice or comments appreciated.

In Building Code Questions | Asked By Frances Bucinel | Feb 10 16
2 Answers

Rigid foam on the roof

We are remodeling the exterior of our 115 year old farm house this year and felt it would be a great time to tighten the envelope and add rigid foam to the exterior. However, our contractor has some concerns about the extra weight of five inches of foam over the roof. Is this a valid concern? It's an old house. The frame of the roof consists of actual 2x4s placed 24 inches apart. We nailed 2x12s to the 2x4s eight years ago to provide a cavity to put blown in cellulose.

Thanks for the advice, Ryan

In Green building techniques | Asked By Ryan Knight | Feb 11 16
Register for a free account and join the conversation


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