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

How to create an air seal

We recently purchased a house that has a room with cathedral ceiling covered on the inside with cedar siding. This room, which was an addition has its own electric forced air furnace. Unfortunately, the builder of this room did not install a air barrier or even drywall under the siding, but did insulate the cavity above. This allows the thin cedar to leak at all of the joints. Blower door test and smoke confirmed the leakage.

I see two alternatives:

1. Remove the roof deck and apply spray foam from above, install a new deck and roof.

In Green building techniques | Asked By Dan | Nov 27 15
4 Answers

Atypical cathedral insulation


I'm in climate zone 5A and trying to determine how to best insulate cathedral ceiling in farm/shop pole-type building with unusual design (picture attached). Building is multi-purpose with large portion un-insulated, but I would like to split loft section in half and use half for insulated workshop. Periodically heating around 60-65 deg at the most (but above freeze level all winter). Code does not apply for this building, but I don't want long term moisture issues.

In General questions | Asked By Matt | Nov 25 15
2 Answers

Can anyone recommend a high quality direct vent natural gas heater?

We are currently using a vent free heater and find that it is causing health problems. Any recommendations or advice would be appreciated. Thank you.

In General questions | Asked By Grace | Nov 25 15
8 Answers

Split system location

If I am going to install a mini-split in a very small, well sealed, well-insulated new home that will need airconditioning rarely (maybe never) but heat more often, does it make sense to install the interior unit at floor level instead of ceiling level? Is there generally an option offered by mfgr of low or high mounted units?

In Mechanicals | Asked By A Lange | Nov 24 15
8 Answers

Solar array positioning in Charleston, SC

Our home builder positioned our solar arrays facing east and southeast, but the angle is pitched east on both. One bank of panels are partially blocked by a large oak tree to the east, the roof of the building to the south, and a 2 level garage which partially obstructs the array (12 in each bank) eastward. The other array is pitched east and catches a glimmer of southern exposure sun, but is partially blocked by other large live oak trees to the south,

In Green building techniques | Asked By F White | Nov 24 15
1 Answer

I am a paid member that can't access product guides

Now I have been blocked?

In GBA Pro help | Asked By Greg | Nov 26 15
2 Answers

How to separate house from garage

Our house will have 5" nail base on the roof with a 3" of oc foam on the underside and the walls will be ZipR over 2 x 6 wall. The garage will attached to the house. My question is do you build a wall in the attic between the garage and living area, then insulate it just like an outside wall? Also I don't want any pull down stairs in the house so what should I do for access to the attic from the garage? I thought about have an exterior door installed in the the previous mentioned wall.

In General questions | Asked By Eric Chandler | Nov 26 15
13 Answers

Ideal load for a multispeed inverter-driven GSHP?

In a planned "Pretty Good House" in Mixed Humid, Northern Climate Zone 4, I intend to use a 45 EER Ground Source Heat Pump with 3 inverters (loop pump, compressor, and fan) with a Cooling Capacity range from 9,000 - 24,000 Btu. I wish to have the lowest Peak Cooling Load, that utilizes the equipment most efficiently, while providing dehumidification and keeps short cycling to a minimum. Approximately what sould that theoretical Peak Cooling load be ?

In Mechanicals | Asked By Ted | Nov 19 15
3 Answers

Inward solar vapor drive with Zip R Sheathing

I am curious if Zip R sheathing would experience any issue with inward solar vapor drive.

We have an upcoming project that will use Zip R Sheathing (in the polyiso 1 1/2" variety) - and will also have a reservoir cladding - stone on the exterior. There will be a minimum 1/2" gap between the back of the stone and the zip - but it won't be ventilated. Still I was curious if the zip coating and osb might allow vapor to be driven through them only to condense at the outside of the polyiso.

In Energy efficiency and durability | Asked By Patrick Kelly-Decker | Nov 25 15
4 Answers

Mineral wool in an attic


This is a complete newbie question.

I read the article about Mineral Wool in Fine Homebuilding 254 (pp. 48-53 September 16, 2015) and it says that if you use it for insulating the floor of an unconditioned attic, you need to use a vapor barrier underneath it.

Would the painted drywall ceiling in the living space below the attic perform that function or do I need to install something in each rafter bay before putting in the mineral wool? Would that thin bubble-wrap-like insulation sheeting work?



In Energy efficiency and durability | Asked By George | Nov 25 15
Register for a free account and join the conversation

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