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!


7 Answers

Recommendations on HVAC Design

Because local HVAC contractors typically oversize and aren't apt to land on the ideal solution for high performance homes, I am considering analysis by a third party like Energy Vanguard for my cold climate ductless heat pump system:

https://www.energyvanguard.com/service-category/hvac-load-calculations

I would like to get some feedback on services like this and any recommendations of alternatives to them. I was quoted $900 for:

-Manual J room-by-room heating and cooling load calculations
-Manual S system specification with Diamond System Builder report for Mitsubishi

In Mechanicals | Asked By J M | Feb 13 18
21 Answers

Radon is 9.3 pCi/L even after radon mitigation — Is this OK?

Hi. I am having elevated ( 9.3 pCi/L) radon after mitigation done. I have an encapsulated crawl space ( insulated, air sealed, dehumidifier ) with piping running under vapor barrier-which terminates to an outside radon fan connected with a 4"PVC pipe. Would like to find out if it's Ok to install drainage ( perforated black pipe) piping under vapor barrier ( in encapsulated crawl) for radon mitigation. The piping is spilt off of a main trunk ( no continuous circle) to different sections under the crawl.

In GBA Pro help | Asked By Hotandhumid | Jan 22 18
6 Answers

Corrugated metal over mineral wool

Hi, I am looking for ideas for installing vertical corrugated metal over Roxul comfort board.

A bit more about the project:
Zone 5B,
2x6 @ 24" OC walls insulated with Roxul batts (R-23),
plywood, wrb, and
2" Roxul Comfortboard (R-8), corrugated metal siding running vertically.

Do I need to install vertical furring a layer of horizontal furring to attach the corrugated panels to? Can the metal be attached directly over the comfortboard?

Thanks for any thoughts/ ideas.

In Green building techniques | Asked By Stacey V | Feb 6 18
12 Answers

250 cfm differential with radon fan: Why?

Hi. I am working on a continuing problem, and hope to get the advice from the smart minds on here to figure out why we have are having both indoor humidity fluctuations and elevated radon ( GBA links to both topics attached below). Trying to solve both humidity fluctuations and elevated radon ( 9.3 pCi/L) with radon fan running. I did close up the 3 small HVAC supply damper vents as suggested in the previous post ( see link below)... thanks! However, we are still having pressure/cfm differential with the radon fan running, based on blower door test done yet again.

In General questions | Asked By Hotandhumid | Feb 12 18
5 Answers

1950 building — bare block walls, no insulation, no drywall — 1 1/2" room to improve?

Northern Ill location -8 " block bare except paint inside and out. Apartment 2 bed forced air nat gas heat New anderson double hung well sealed.
Will put treated 2x2" interior frame to put conduit for new circuits--only 2 circuits now -kitchen and everything else. flat roof with 2x10 insulated. So do I go plastic vapor barrier then 1 1/2" sheet foamboard between studs? or just foam board or building wrap over or under foamboard. No AC.

So now condensation point is in block wall and has been forever. If I move it in -will I create a water making machine?

Any Ideas?

In Energy efficiency and durability | Asked By Scout159 | Feb 10 18
20 Answers

Basement insulation

Hi! I appreciate all the forum advice I get from your organization. I am seeking to take over my Dad's residential construction business and I am designing my own house which we will build in a few years. I am in college to do so and am learning an awful lot. For basement insulation, I narrowed down some ideas that I would like to go with. To let you know some of our practices, we dampproof our basements and run drains around the perimeter just in case. As for the insulation, upon much research, I have found that it is best to use sub-slab insulation. We live on the southern edge of Zone 5.

In Green building techniques | Asked By Golfm02 | Feb 12 18
5 Answers

Is foamboard and stucco to the ground in a pier and beam house a termite risk?

SUMMARY: I'm contemplating installing foamboard + stucco over existing wood siding, running it all the way to the ground on my pier & beam house, but worry whether this could invite termites.

In Green building techniques | Asked By Michael Bluejay | Feb 12 18
3 Answers

Heat pump for a remodel - Questions for a remodel in a Marine (3C) zone

Thanks for your thoughts in advance!

I've been reading everyone's comments and so many articles to come up with efficient ideas for an impending remodel, and I'm curious what others think at this point.

I'm in zone 3C (Marine), and the ocean moderates the climate in my neighborhood so heavily that it's always slightly chilly, but never freezing. No one installs air conditioning.

In Mechanicals | Asked By Dirtfox | Feb 12 18
8 Answers

Under slab insulation in tropics

We have a house in the Florida Keys, where the house is build on a concrete slab 9 feet above grade, supported by concrete columns. There is a separate slab at grade where we park vehicles etc. The summer sun reflects off the slab at grade and heats the underside of the raised slab, where the parts getting this reflected heat are noticibly hotter than other parts away from the sun. This is placing a large load on the airconditioner on top of the normal very high ambient temperature. Is there a simple way to substantionally reduce this heat input into the house in summer?

In General questions | Asked By J2V | Feb 11 18
9 Answers

Oversizing a multi-zone inverter heat pump - does it matter?

I'm trying to figure out a strategy to heat a large one level house with many rooms, and it seems that a multi-zone mini split could give me the overall capacity I need with the greatest comfort. But I've also seen many warnings about oversizing and its ultimate effect on COP, which makes me a bit nervous.

Looking at the heat pump specs, though, I'm confused as to why there would be a problem. My heating contractors aren't necessarily heat pump engineers, so I'd like to run some thoughts by the contributors to see where I might be off base.

In General questions | Asked By rk2 | Feb 11 18
Register for a free account and join the conversation


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