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!

15 Answers

Sleeping coves betters than medium sized bedrooms?

I redesign old homes and rent them out. I found hallways are your worse enemies in use of space. It was not until this last year that I noticed hallways in my rentals that I didn't mean to make.

Lets take a bed of roughly five foot by seven foot for example. If I put this bed in the middle of the room with the headboard on a wall and put three feet around the bed I get a 11 foot by 10 foot bedroom. A typical bedroom size plus or minus. In this typical bedroom I have a roughly five foot by two foot closet.

Current Rental / Bedroom / Square Footage

Asked By S E | Oct 13 14
10 Answers

Unintended vapor barrier using oil-based stain on wood?

I need to stain some new bookcases (floor-to-ceiling) located on exterior walls. I want to use oil-based stain but am concerned that may act as a vapor barrier. The literature and other posts discuss the need to avoid vinyl wall paper or oil based paint on the wall in my climate zone (2B). Does oil-based stain (probably with varnish top coat) on the book case fall into this same category? The wall-to-book case surface of the book case is unpainted.

Asked By John Walls | Nov 16 15
3 Answers

Zoned HVAC and dampers — Opinions?

Townhome has a zoned (3-levels) HVAC system. This system contains four trunk lines off the supply plenum one of which contains a weighted (manually adjusted) damper that was originally routed back into the supply plenum. This weighted damper is designed to provide bleed off air when less than 3 zones are in use.

You would adjust the damper by so that is operated as follows:

3-zones in use (damper is basically closed)
2-zones in use (damper partially open)
1-zone in use (damps is slightly more open vs 2 zones in use).


Asked By Chris M | Nov 18 15
3 Answers

Downloading Details

Details will not open in Autocad LT 16
Any Advice?

Asked By Carole Coelho | Nov 18 15
7 Answers

Need a stealthy ERV installation

Hi, I own a 1450 SQFT home that has been spray foamed throughout (walls, attic, etc.) and has decent triple pane windows, but minimal to no passive solar due to orientation and surroundings. Although the home is 75 years old, a blower-door test revealed its tighter than most new builds, so I need a ERV as soon as possible. I chose an ERV over an HRV due to the humid summers and long dry winters here in MN. The home has a 96% efficiency gas furnace and central AC. The furnace has a multispeed fan.

Asked By Ryan Griffin | Oct 23 15
2 Answers

How to use polyiso as interior insulation on a pole barn?

I have an unfinished pole barn with board and batten siding in Pennsylvania. I'd like to insulate the inside with polyiso panels, because that way I won't have to frame out the walls, and the polyiso will create a handy air barrier and thermal break. I can also find used 3" panels for ~$20 around here. My plan is to glue 3 inches of polyiso directly to the inside of the Purlins, tape the seams, then screw OSB, plywood, or drywall on top with long screws. These screws will go all the way through the foam to the barn's 2x4 purlins.

Asked By Jack | Nov 17 15
1 Answer

Venmar C12 HRV vs. Venmar E15 HRV

Is anyone familiar with the differences between the Venmar C12 HRV / ERV series and the E15 ECM HRVs? The E15 ECM HRV is about $650 more expensive. I'm having it installed in conjunction with existing furnace ducting, but hope to not use the furnace fan to distribute the air.

So I'm mainly looking for advice on whether the features or efficiency of the E15 is worth the upcharge here.

Thanks for your help!

Ryan Griffin
1450SQFT low energy home
Minneapolis, MN

Asked By Ryan Griffin | Nov 18 15
5 Answers

Control a heat pump with a wall thermostat?

I have recently installed an airsource heat pump in my vacation house in central Vermont. It works great, and mostly replaces the electric baseboard heating.

My concern is that the unit can only be controlled by a hand held remote, and only goes down to 60 degrees. We normally leave the house at 45 when we are away. It seems to me I am wasting a lot of energy now, perhaps using even more than the baseboards at 45.

Asked By Philip | Nov 17 15
32 Answers

Vapor barrier or vapor retarder paint on open-cell spray foam?

I have seen some tout using the vapor barrier paint directly on open-cell foam before covering with Sheetrock, but as of late a general air of negativity towards that approach. I intended to use MemBrain under my drywall, but the open cell installer claims the paint works just as good for half the cost. What are thoughts on this? The stack up is a 2x6 wall with 2x2 interior Mooney strapping for a 7" thick OC foam fill wall over Zip board, taped of course. Then followed by a fired out ventilated assembly with Hardi siding.

Asked By Joe Suhrada | Oct 29 15
1 Answer

Blown-in insulation on open vaulted ceiling

I am had built with the plan to blow in insulation, and now that Im about to do it my mind is struggling with some physics.

I ceiling joist to the roof rafters with the help of an engineer to vault my upstairs bedrooms. This leaves me with a void of half the difference shown in the diagram attached. My question is will 5/8 drywall secured at 16" on center handle the load of blown in cellulose? If the insulation blows in as shown by the shaded area there shouldn't be any more than 18-20" over an given area. My biggest concern of course is how this would settle over time.

Asked By Marcus | Nov 17 15
Register for a free account and join the conversation

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