Q&A: A Forum for Green Building Experts and Beginners

[Click map to enlarge]

Please register for a free account or sign in to ask and answer green building questions.

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!

14 Answers

Bug screen for rainscreen strapping...how wide to cut?

I'm a rookie with this. First time building a rainscreen. I've got my WBB on the house and would like to apply my 3/8 strapping to create and airgap.

I picked up a few hundred feet of 4' bug screen and I will first apply a layer top and bottom, then my strapping and then staple the bug screen on-top of the strapping making the air gap, hopefully, bug free.

In General questions | Asked By Mark Helmrich | Mar 18 15
6 Answers

Small addition

I am in the early design phase of a small (12'x20') addition for a client in climate zone 5 and am just looking for suggestions as to the best new construction insulation & air sealing details to use.

It will be wood frame construction with a crawl space and a gable roof with vaulted ceilings inside.

I am leaning toward the zip wall sheathing system on walls & roof deck with a rainscreen on top and fiberglass batts in the 2x6 stud bay. Is the zip wall roof sheathing of sufficient thickness to allow me to build an unvented roof without having to spray 2-part foam on the underside?

In Energy efficiency and durability | Asked By Jason Schatz | Mar 24 15
2 Answers

OSB for rainscreen furring?

Hey all - I'm going to be residing my single story house this summer (climate Marine 4c - Seattle). The walls look like this (inside to out):

Gypsum > 2x4 cavity (to be filled with dense-pack cellulose) > 1x8-1x10 shiplap sheathing > 15/30 lb Felt, taped > 1" polyiso > OSB furring (with core-a-vent sv-5) > hardie plank/cedar shingles.

In Energy efficiency and durability | Asked By Mateo K. | Mar 24 15
6 Answers

Filtration and humidification with mini-split systems

I have a customer with allergies. Her existing GFA furnace has a high efficiency filter and a humidifier.

In the new (air sealed and super insulated) home we are designing for her, we are planning to use Fujitsu mini-splits for heating and cooling and a Honeywell ERV for ventilation. Specs for these units indicate a washable filter but no MERV rating.

In Mechanicals | Asked By Terry Herschberger | Mar 23 15
3 Answers

Thicker walls

I live in Minnesota. I'm remodeling an older home with full 2x4 studs. On the outside there is a layer of 1 inch buffalo board and 1 inch foil covered foam.
Is it worth the time and money to add wood strips to the 2x4's to make them 2x6's on the inside and go from a R-15 to R-19 or 21 insulation or add 2 inch certifoam to the outside or should I just leave it alone with 2x4 walls and R-15?

Thank you

In General questions | Asked By Scott Neels | Mar 22 15
3 Answers

Foil tape inside duct?

I have several heat registers that I can access the duct from the inside only on, a few as far as 2 feet into them. Some just have seems, one has a good 1 inch gap on one side. (I'll try to hammer that together from the inside.)

Anyway, I've read that mastic can dry out on the inside of ducts, but have read conflicting suggestions about foil tape. I have this tape right now, should it work on the seems inside the duct, in the last 2 or so feet before the register?


In Mechanicals | Asked By Jeremy M | Mar 23 15
2 Answers

thicker walls -- [Not really a new thread]

The interior is gutted to the studs. Was going to replace old isolation with R-15. Will be residing in the future. Vinal is brittle and we are replacing all windows. Doing all the work myself so it's just what I think I'm worth.
Thank you

In General questions | Asked By Scott Neels | Mar 23 15
2 Answers

Hard or flaccid?

I am advising my friends on their 50s ranch upgrade with full basement. The house could never be made energy efficient unless it was completely torn down and rebuilt. They have a lower seer HVAC system that is a tad bit over-sized and runs like a top. Their GC wants them to completely rip-out the very accessible (full basement) hard HVAC duct and install a new system for 16k+ not including 18% markup (estimate with no manual J or D, to go by I might add), because their system is "too leaky" which he summarized by just eyeballing it.

In Energy efficiency and durability | Asked By leo kloop | Mar 23 15
9 Answers

New PHIUS+ 2015 released and in effect as of March 16th, 2015

Interested to hear comments on the new PHIUS + 2015 that went into effect on March 16, 2015. They made a lot of changes and the biggest being the each climate zone and specific area will have its own standards. Not one big gigantic fits all approach like PassivHaus but very specific to climate zones, house size, etc.

Read more here:

In Green building techniques | Asked By Peter L | Mar 20 15
0 Answers

Question re furring strips, XP drywall, and finishing basement over 3" of polyiso

I have used recycled roofing polyiso panels (1.5" stuff), staggered them, and going to foam the gaps where I can and use acoustic sealant ("the black death") on gaps too small for foam.

Here is a big question, I want to put furring strips horizontally and just mount drywall over that:
1. Is it OK to just go with furring strips and not build out full 2X3 or 2X4 framing. Wasn't planning to fill the gap with anything between drywall and polyiso

In GBA Pro help | Asked By Apollo S | Mar 23 15
Register for a free account and join the conversation

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