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!

2 Answers

Hydronic radiant design questions

Hello GBA,

I posted a pretty naive question last week regarding selecting the proper heat source. I'm not an HVAC expert by any stretch but as an owner of multiple degrees and a home improvement nut, I don't want to back away from this just because it is quite a bit more intricate than I realized.

In Mechanicals | Asked By Brian Gray | Nov 11 14
1 Answer

I have a detached garage with a hip roof, and the garage is open to the ceiling without rafters

I have a detached garage with a hip roof, and the garage is open to the ceiling without rafters. I had a ridge vent installed but the venting is only in the center and not extended to the hip portion of the roof. I am currently in the process of installing


In General questions | Asked By Edward Millward | Nov 11 14
19 Answers

What heating system should I install in my 150-year-old house in Connecticut? Oil boiler, ductless minisplit, or something else?

My family lives in a 2-story 2000-sq.ft. balloon-framed house in Western Connecticut (zone 5A). We currently heat exclusively with a Harman XXV pellet stove, which surprisingly keeps most of our house pretty comfortable even in the depths of our cold New England winters. Of course there are some rooms that will get down below 60 on the coldest of nights, but that just means we stay in the warm parts of the house, which works fine for us. We used to heat with a Burnham RS-111 oil-fired boiler piped through about a dozen beautiful and massive cast-iron radiators.

In Mechanicals | Asked By Rob Wotzak | Nov 9 14
4 Answers

Is there an equation that will tell me how relative humidity varies with temperature?

I live north of Seattle and the winter humidity in my partially earth berm home runs 70%. The outside air temp tonight is 45 degrees and 95% humidity. I am trying to decide between ventilation and a dehumidifier. I would like to know at what RH that outside air will have after I warm it up.

In General questions | Asked By Mike Roberts | Nov 10 14
1 Answer

I have a Carrier high-efficiency propane furnace in suburban DC. Is 50 degrees too low to set the thermostat during the day?

During the winter while at home we like it at 70 or 68 if we are dressed warm. No one is at home at least 8 hours during the week and sometimes all weekend.

In Energy efficiency and durability | Asked By Tom Earnest | Nov 10 14
1 Answer

Can I add Roxul RockFill behind finished wall?


I have a finished condo with columns around the perimeter surrounded by drywall. Those columns are currently filled with a small amount of pink insulation. I can detect air currents coming out of some of the outlets on the columns. I was wondering if tightly packing Roxul Rockfill (http://diywithroxul.com/en-us/rockfill.html) along the base of these columns behind the drywall via the electrical outlets would negatively affect anything, given that I'd only be putting the insulation at the base and it would be mixed with the existing pink insulation.


In Energy efficiency and durability | Asked By Green Scape | Nov 9 14
3 Answers

Weathertightness of solar mounting hardware roof penetrations

Hi there,

I am in the process of reaching an agreement to have my leased PV array on my roof deinstalled, and I have a question for the professionals re my roof.

In short, while I'm not going to get into a number of the details or legal stuff here, I'll stick with the most basic facts: I've had a brand new second story since 2008, which was insulated and airsealed by a county-approved weatherization crew in that year—big checklist, blower door test, lots of sealing and cellulose and attic boxes and all the rest. It met/exceeded targets and it performed very well.

In General questions | Asked By Minneapolis Disaster, 6B | Nov 8 14
8 Answers

Planning for solar

The house I'm building will have a pretty good roof for solar. It's a simple 8/12 gable, with the south side facing a little east of south. The only real shading will be birds and clouds.

I'd like to install a metal roof, for a variety of reasons. Any suggestions for making sure the roof will work well with solar? Extra fasteners? Heavier gauge?

I'm leaning towards standing seam, but they aren't cheap, especially the galvalume variety. I'm open to other types of metal roofs.

In General questions | Asked By Graham Fisher | Nov 3 14
4 Answers

Duct heater required with an HRV in a cold climate??

I'm in the beginning stages of building a super-insulated house near Ottawa, Canada. The foundation is completed and we're about to start framing. One of the last details / sub-contractsI need to tie up is the HRV system. One of the firms providing a quote insists a 1500-2000w duct heater is required.

I recognize that the fresh air is likely to be somewhat cooler than the temperature of the house. However, this suggestions a little over-the-top given that the house will have R50 walls, R80 attic, tripled-glazed fibreglass windows and will be tight at less than 1.0 ACH50.

In Mechanicals | Asked By John Scime | Jan 16 12
10 Answers

Powered direct-vent gas water heater recommendations?

My water heater is on the last legs (just started to leak). The current unit is an atmospheric vented unit that is located in the basement. Based on Martin's article (www.finehomebuilding.com/design/articles/the-water-heater-payoff.aspx) it appears that a power direct vent (sealed) or gas condensing is the best way to go for a basement location. Besides minimizing drafting and makeup air issues, I like that I can eliminate the vent to the roof.

In Mechanicals | Asked By Brad Stoppenhagen | Nov 4 14
Register for a free account and join the conversation

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