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

Deck footers

Good evening Everyone,

I'm attempting to build my first deck this spring. I've dug holes for footings and just passed my footing inspection.

The Deck code here in maryland dictates that holes are to be a minimum of 30" deep with an 18" wide by 10" deep concrete footing. Once you have that you can either use concrete piers to get your posts out of the ground or you can place the post right on the original footing.

In Building Code Questions | Asked By Andy Pappas | Apr 17 17
4 Answers

DensArmor in bathroom

We installed Dens Armor in all the bathroom, walls and ceilings.

We are putting in full showers, already manufactured, no tile work on the walls. The master bath is an Onyx Shower. Cement board is going on the floors for the floor tile work.

Is the Dens Armor suitable for the walls surrounding the shower?

Dens Armor in the kitchen for the backsplash by the sink, looking for recommendations if for a wall underlayment.

In General questions | Asked By Bridget Lamberson | Apr 17 17
1 Answer

Bathroom exhaust vent sizing in 2x4 walls

We recently bought a front to back split so there are essentially three levels with our master bedroom and bathroom at top. It turns out the bathroom exhausts for all three bathrooms run into the attic but luckily there doesn't appear to be much mold. They used flexible duct.

We are replacing all of the old, rattling fans ducts, but we have 2x4 interior walls and a long run for the basement bathroom.

Can we use rectangular metal duct for the vents or do we need to stick to round?

In Mechanicals | Asked By Allysn Moore | Apr 18 17
1 Answer

Housewrap under rigid foam AND taped rigid foam at windows

the set up: Climate Zone 3. I'm using a standard house wrap between the OSB sheathing and the 1" rigid foam. The rigid foam will have all seams taped and will act as the primary WRB behind 3/4" vertical furring and lap siding. The Question : How do I terminate the house wrap at windows? just bring all the way into the "outtie" window bucks (caulk to buck), install rigid foam, then install window peel and stick flashing on bottom/part way up the sides. Install window. Would you recommend a 2nd layer of house wrap around the windows? Attached to the rigid foam?

In Green building techniques | Asked By Inger Peters | Apr 17 17
12 Answers

Are minisplits not allowed as the only heat source?

We are in Minnesota (Zone 6a). Building this summer on 12 acres. 2200 sq/ft single level (maybe a bonus above garage), slab on grade.

After speaking with the first HVAC company, they claimed that the LJ's would not allow mini splits as the primary heat source in a home. I would have to install baseboards, in floor heat, etc. They said I would be required to have a heat source in every room. I got the sense they were trying to sell me on radiant, which I have learned, I can comfortably avoid if I insulate the slab well (they also disagreed with that).

In Mechanicals | Asked By Scott K | Apr 15 17
12 Answers

TwinFresh Comfo 32 CFM Power 5 in. Single-Room Energy Recovery Ventilator

I just took ownership of the first HRV to be sold at Home Depot. I love it.

Price $475

Extra stuff I learned about it:

1. The 16cfm mode (perfect for a 2 person bedroom) is only 0.3 sones at 4 watts. Almost inaudible.

2. Low speed is 8cfm (the one person setting) is 0.1 sones which is TOTALLY inaudible.

3. It can cycle on humidity if desired. That is, it will come on when the humidity reaches 40%RH (low), 50% (medium), or 60% (high). When the humidity drops below the setpoint, it shuts off.

In Mechanicals | Asked By Kevin Dickson, MSME | Jun 6 14
5 Answers

Preferred window/door sill flashing tape?

I've been looking for some water-proof/vapor closed window sill tape alternatives to the pro clima extoseal.

Planning on using vapor permeable tape for pretty much every other application but I've been told it's best practice to use a vapor closed tape at the window sill because this is the one place where water may sit for longer periods.

What is your guys preferred tape for this application?

In General questions | Asked By Grey wolf | Apr 15 17
4 Answers

We are building a house in Hanover, N.H.

Based on discussions from GBA, we are adding 2 1/2" XPS to the exterior of the sheathing. What is not clear is what (if any) treatment occurs near the ground level -- i.e., on the bottom edge of the 4x8' panel of XPS.

If left exposed, is it susceptible to rodents, bee nests, etc? The siding will be Hardiboard.

In GBA Pro help | Asked By Frank Torti | Apr 17 17
6 Answers

Aeroseal duct work

Had my hvac system aerosealed. The air return system had leaks equal to an 18 inch square hole. They sealed it until it was ok. The service ducts checked out ok,so they did nothing to it.. But I still have a terrible dust and filth problem. They unhooked the flex duct(which goes to the room vents) from the main trunk line and plugged the holes and checked it that way. Should they have sealed off the individual room vents and checked it that way instead of sealing off the lines at the main trunk line? The hvac system is about 2.5 years old.

In Energy efficiency and durability | Asked By Alcoaky | Apr 15 17
7 Answers

Airtightness review and OSB?

I'm finalizing the specs on our energy efficient home and am looking for your comments on the following details:
Wall: metal siding, strapping, 3" Roxul Comfortboard, Tyvek Commercial WRB, 3/8" OSB with taped seams, 2x8 studs 16"OC, Roxul, 6mm poly AVB, 2x4 stud service cavity, 1/2" drywall.
My biggest concern is the lack of air tightness of the OSB, and if that will be solved by taping the seams and using the Tyvek Commercial wrap.

In Plans Review | Asked By Terry Goodwin | Apr 17 17
Register for a free account and join the conversation

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