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!


5 Answers

Supply-only ventilation with dehumidifier ?

The house will be a 2200 square foot house in Zone 4A. At this time the house is planed to be as tight as I am able to get it with in reason.

My question is, is there any reason not to use the fresh air option on a stand alone whole house dehumidifier such as the Honeywell TrueDry 90 as the ventilation source ?

I ask as I know one of the bigger IAQ problems in the home will be humidity.

In Mechanicals | Asked By Jared Humphrey | Apr 29 12
5 Answers

Making exterior crawlspace foam more termite resistant

I"m building a tiny house in southern Illinois, zone 4, mixed-humid. Dry-stacked CMU crawlspace outside dimensions ~18' x 18' with 2" rigid foam for ~R-10. Since the interior & exterior of the block will be "plastered" with surface bonding cement (SBC), would the following work to inhibit termite entry:
1. Install the foam board with thinset mortar (1/2" notch) including to the footings?

In Green building techniques | Asked By Harlan Bauer | May 1 12
37 Answers

The example of the failed roof with the polyiso on the interior.

It appears this sandwich had fiberglass in the roof cavity?

I was thinking of using 1" poly iso on a cathederal ceiling to give a thermal break to the framing. Spraying poly iso 4" closed cell 2# foam in the rafter bay. Then adding the additional inch of sheet foil faced on the interior. With the closed cell we have never had a moisture problem occur. Our location is north eastern Pennsylvania. The roof system has ice and water shield on it. Our feeling is that the closed cell foam doesn't let any air leaks occur, keeping moisture out of the interior to exterior sandwich.

In Energy efficiency and durability | Asked By Joe Billingham | Aug 11 10
5 Answers

What works best under a foam exterior?

I've watched the videos on installing foam board on the exterior of a house but what does the foam sit on at the the sill plate? I'm leaning towards a metal drip edge but others use Azeck board.

The reason I ask is that the videos address the windows well but what about the doors. We are not planning on putting bucks at the rough openings of the doors, just the windows. Since the door frame will be hanging out over the foam I just wanted to know how to support it if I use a metal drip edge like in the videos.

I also need some advice on a bug screen, what should I use?

In GBA Pro help | Asked By john bell | Apr 30 12
0 Answers

A real use of GEO-T systems with 100%Priority HW series

Specifically who has installed systems with the full condensing series DeSuperheater-Priority HW On-Demand that as HVAC-GT-HW-Reclaims all of the heat from a cooling mode? It also acts as a DeSuperheater in heating mode, and can continue in a convection of hot water heating if plumbed for that. and other applications as well.

In Mechanicals | Asked By JP Jon Pierce | May 2 12
5 Answers

Attic HVAC and Radiant Barrier

As part of a major renovation/addition to our 1970 2 story colonial house, we're isolating the 2nd floor HVAC and adding a second zone for it, and the contractors want to place the equipment in our unconditioned attic. It get's pretty hot up there in the summer (even though I live in NJ), and I want to do what I can to maximize the efficiency of the HVAC equipment in the attic.

In Energy efficiency and durability | Asked By Eric Lavitsky | Apr 30 12
7 Answers

Is it possible to install cement siding to SIP panel with additional exterior foam?

Seems to be a lot of concerns regarding the use of exterior foam and cement lap siding attached to just the exterior skin of a SIP panel.

I was hoping to bring the exterior plane of the SIP wall in line with the 2" ICF foundation wall foam. My plan was SIP, 15# felt or housewrap, 1.5" foam board, 1/2" ripped plywood furring for drain plane, and cement lap siding.

This type of detail is readily available if you are attaching to a stud wall, can't find a similar detail for a SIP because of concerns about the ability of the OSB SIP skin to hold fasteners.

In Energy efficiency and durability | Asked By Kevin Klein | Apr 30 12
2 Answers

Will Bin (shellac-based primer) over 1.5" of 2-pound foam over 6" of polyiso in 2x10 rafter bays give me a vapor barrier?

In a Massachusetts coastal home I have 6" of polyiso in the rafter bays. If I spray 1.5" of 2 pound closed cell foam I get close to a vapor barrier. Will painting/sealing the cured foam with a shellac based primer (like Bin or Killz) give the code required warm side vapor barrier?

In Energy efficiency and durability | Asked By John Gorman | Apr 30 12
3 Answers

What window assembly has the highest U-factor?

I'm trying to buy windows and would like to know which assembly has the highest U-factor.

In Energy efficiency and durability | Asked By eric lechuga | Apr 29 12
18 Answers

Metal roofing

I am thinking of replacing my roof so I'm wondering about the benefits of a standing seam metal roof. I'm aware of its greater durability, but I'm wondering about the energy efficiency component. Does the energy benefit come mainly from choosing a light color? Do light colored asphalt shingles offer a comparable energy benefit?

In General questions | Asked By David Martin | Apr 19 12
Register for a free account and join the conversation


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