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!

5 Answers

Rainscreen - tie into soffit at top?

If there is an air path to the soffit, when creating a rainscreen assembly, is it sufficient to vent the top through the soffit, or does the siding need to have an opening all along it's top edge as well?

In Green building techniques | Asked By John P. | Jul 7 16
2 Answers

Roof foam - 2 or 4 layers?

I'm insulating the exterior of a gambrel barn. The roof needs 8" of XPS insulation, and I'm wondering if two layers of 4" foam will sufficiently block airflow to the roof deck, or if I would be better off doing four layers of 2" foam. I'm doing this myself, so 2 layers will be easier to handle, I think


In Green building techniques | Asked By John P. | Jul 7 16
11 Answers

Please help me decide which option to go with for my encapsulated crawlspace retrofit.

I am in Nashville, TN - zone 4. I just bought a two story house that was built in 1997 and is on a crawlspace. The current crawl is in "good to great" shape according to the various contractors and energy professionals that I have had down there giving me bids. This is even though I have already fixed numerous issues with overflowing gutters or gutters with downspout connections at the ground level that did not correctly meet up with the black pipe to take it away from the foundation.

In Energy efficiency and durability | Asked By John Sexton | Jul 5 16
8 Answers

Expensive electric combo boiler or cheaper electric boiler + water heater?

I've been siphoning off valuable information as a non-member for ages now, but no one seems to have spoken online about my current situation, so I'm happily forced to join the movement!
I'm contracting the build of my Southern Ontario as-close-to-Net-Zero-as-possible house, and have been left with two wildly disparate quotes from HVAC contractors to take care of my hot water needs. The system will be electric boiler-driven radiant floors throughout the 3200 sq. ft. home (wood stove backup), with accompanying HRV.

In Mechanicals | Asked By Jason Jazrawy | Jul 5 16
9 Answers

Basement egress windows

I am currently getting bids for interior drain tile and the addition of a basement egress window. Two companies I have spoken with have indicated they will dig down to the footer under the egress windows repair any cracks, and refill with washed rock within 8" of the bottom of the window opening, install fabric and then another 4" of washed rock. This method in essence will tie the drainage under the egress into the perimeter drain tile system.

In General questions | Asked By M S | Jul 3 16
2 Answers

Ventilation calculation consternation

Are the following ventilation calculations correct?
Per (2013) ASHRAE 62.2 we need 3 cfm per 100 square feet plus 3.5 cfm per person.
So, a 3000 sf home with 5 occupants requires 127.5 cfm.
That's 7,650 cf per hour...
or 183,600 cf per day.
If the 3000 sf home has 8' ceilings, the total volume is 24,000 cf.
183,600 / 24,000 = 7.65
So, we're supposed to ventilate enough to change all the air 7.65 times per day?

In Mechanicals | Asked By Ben Rush | Jul 6 16
2 Answers

Minisplits are cheaper? Really?

Los Angeles rental. Installed an off-brand mini split years ago and now need to replace it. Over the last couple of weeks I have called 27 AC contractors, many recommended from the Fujitsu or Mitsubishi website. I am asking for a 15k Mitsubishi, Fujitsu, Daikin, or even an LG with at least 18 SEER, preferably 23 or greater. Outdoor unit is directly below indoor unit; 220 v. receptacle right there. 7' exterior line drop.

Looking at the website distributors, seems the material cost is <= $2,000. Probably 4 hours for the installation. It's L.A., so figure another two hours for traffic.

In General questions | Asked By David McNeely | Jul 6 16
1 Answer

How to frame in a window with continuous insulation

I am building a one level SFR with 2x6 walls w ZIP sheathing, using Senergy Platinum CI stucco system on the exterior and high efficiency WS Contemporary Series windows with a flush frame. It looks like the exterior wall system will be roughly 8-3/8" thick from drywall to stucco. We'd like to recess the windows as much as possible, perhaps 4" on the exterior. The windows are 3-1/16" jambs without a nailing flange, which totals about 4.5" for the window frame.

In Green building techniques | Asked By Tracy Lewis | Jul 7 16
8 Answers

Insulation opportunity: re-roofing a 1922 house

I've scoured the archives as best I can and despite lots of great information I've had trouble applying what I've learned to my specific project. Our house is a 1922 craftsman style home with a finished attic. There is currently no access to the unfinished edges or peak of the attic so we're hoping to upgrade our insulation situation while the roof is off.

The house has gable vents that access the unfinished corner edges and peak (4 per side of house).

In Energy efficiency and durability | Asked By Jeremy Cram | Jun 28 16
6 Answers

1.5-inch to 2-inch exterior insulation / fiber-cement siding in Memphis

Been lurking for too long! Hello glad to B here. I have T1-11 over 1" polyiso on 1979 two story 2x4 stick home. I'm looking at >http://thermalbuck.com/. for my Pella casement windows. I thank you in advance for any advice or critique. The T1-11 is currently my WRB. I appreciate Mr. Holliday et.al explaining why long bolts through semi-rigid insul-board is "special" due to shear. My focus is max bang for least bucks while minimizing R bridging in 1.5-2 inch exterior insulation foam. If we can use non-solvent adhesives like Henry 444 FRP with polymer nails like

In Energy efficiency and durability | Asked By Charles Thompson | Jul 4 16
Register for a free account and join the conversation

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