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!


4 Answers

Sub-slab drainage stone size

I know the typical recommendation is 3/4" no fines. Foundation contractor and stone supplier are recommending I use 1.5". Foundation contractor is trusted and has used product a great deal including under some very dry basements that I've been in. Stone guy says he has 3/4 no fines - but it's more money for no gain. I have seen the product they are calling for; it's a mix of ragged and round stone that would surely drain very well. I can tractor stone in, so will be able to minimize trying to stick a shovel in it. SDR 35 interior footing drains.

Asked By Jim Tyler | May 13 16
4 Answers

XPS brands: Dow; Owens Corning; Pactiv/Kingspan?

I would appreciate feedback on the brands of XPS relative to one another.

I'll be installing a double exterior layer next week. Right now I can buy 3/4" sheets of the Pactiv/Kingspan XPS sold by Lowes for $13.57 a sheet (4x8).

Has anyone had any negative experience with the Pactiv/Kingspan foam?

Thanks!

Asked By Bill Daugherty | May 5 16
6 Answers

Does the EER matter on a ductless mini-split?

The Energy Star requirements for ductless mini-splits are identical to split air-source heat pumps, with SEER, EER, and HSPF efficiency standards. However, several utility programs have chosen to drop the EER requirement (e.g. Energize Connecticut).

Does the EER matter on a ductless mini-split? Why or why not?

Thanks!

Asked By Whitney Larsen | May 13 16
8 Answers

Dense-packed cellulose wall insulation

Hi everyone, bit of theoretical question here. Could a wall be designed that would allow cellulose to be blown in at a lower density than "dense-packed" and any settling that will occur is accounted for in the design? (see below). Obviously cavities below windows would need to dense packed. I guess what I am asking here is does dense packing improve wall performance in other ways other than R-value vs loose filled?

Thank you

Asked By Oliver Neumann | May 12 16
3 Answers

Strategy to insulate interior wall exposed to roof cavity

My home is a brick colonial style in climate zone 3. Our main roof is 4-side hip and is encapsulated and contains our upstairs HVAC system. A secondary elevation is over the garage and adjoins the wall of the two south-most bedrooms. This one is 3-side hip with a flat top (architect bad a math) and is ventilated with soffit vents and a powered fan tied to a HA system.

Asked By Dan Geist | May 13 16
5 Answers

Dow Powerhouse Solar System 2.0 PV shingles

An architect I know asked about these (www.dowpowerhouse.com/Solar%20System/). I found Martin's review from 2012, and I wonder if anyone has more recent experience?

Thanks,

Andy

Asked By Andy Engel | May 12 16
32 Answers

Transoms and Ductless Minisplits

Hello,

I am trying to heat and cool my second floor with one 12,000 btu ductless minisplit. I have heard that this is possible if I keep the bedroom doors open during the day to facilitate circulation of the hot or cool air.

However, does it get uncomfortable quickly in the night when the doors are closed. If so, I was thinking of putting in operable transoms over the doors. The only problem is they are kind of expensive (~$275 from transomsdirect.com). Attached is my floor plan. I will be putting ceiling fans in each bedroom so maybe the transoms would be overkill?

Asked By Jimmy Nguyen | Mar 10 16
33 Answers

Insulating a *vented* cathedral ceiling

Hi all,

I'm in a bit of a unique spot, and having read (and re-read, and re-read again!) Martin's article, "How to Build an Insulated Cathedral Ceiling," I have a couple of options and I'm wondering folks' thoughts on the best option.

First, my situation:

Asked By Chris Conti | May 10 16
25 Answers

New slab with radiant heat

As part of our remodel north of San Francisco (ZIP code 94941), we are converting about 700SF of our lower level into living space. The existing slab has been removed we excavated a few additional inches to increase our ceiling height, and we are getting ready to put back a new 5" slab, in which we will also add radiant heat tied to the rebar.

Asked By Torsten Budesheim | Apr 22 16
8 Answers

Mini-split vs forced air and attic insulation

So hopefully a simple question. I'm building a home and have not decided if I should use mini-split or traditional HVAC.

If I use HVAC, I was going to close-cell spray the attic.
Do i need to do this if I'm running mini-splits?

The house is 2400 sq ft so it would have a multi-zones. I presume the refrigerant lines would be running in the attic. do I need to worry about loss there that would warrant spending the cash on spray foam on the attic? Or could I go with traditionally insulated attic since I would have no ducts.

Couldn't I just insulate the lines?

Thanks as always!

Asked By Mike W | May 6 16
Register for a free account and join the conversation


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