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!

1 Answer

What is the cutting edge for window insulating shades?

i have SE facing great room with a vaulted ceiling with many windows and want somethig for year around use.

In Energy efficiency and durability | Asked By ron nienhuis | Sep 19 12
4 Answers

Is additional insulation necessary when installing PVC ceilings?

We are currently building a new home. I've read that PVC ceilings have excellent insulation properties. If we install these, will it be sufficient or is additiona insulation in the roof necessary?

In GBA Pro help | Asked By Rentia Verster | Sep 19 12
1 Answer

Photo needed again -- Flex ducts in attic

Martin has an upcoming article in FHB on energy modeling software. We thought that a photo of a flex-duct octopus may illustrate not-so-good planning.

Anyone have a 'what NOT to do' photo?

It seems to me that I have seen some of these pics on GBA in the past; anyone remember which thread they were in?


In Mechanicals | Asked By Daniel Morrison | Sep 19 12
5 Answers

Wall and Roof Assembly for Hot-Humid Zone 1A--Hawaii

I'm building a new custom home designed to look like an early-Hawaiian stucco structure (think thick walls). It's wood framed with 2x8 stud walls, sheathed with 5/8" plywood (not OSB), with 3/4" XPS foam sheathing over that, and clad with 3-coat portland cement stucco. The exterior windows and doors will be recessed 4" into the walls. We're using the XPS foam sheathing to reduce thermal bridging through the studs, but also to add wall thickness. The house will be air-conditioned, but in use will mostly be open to the trade-winds.

In Energy efficiency and durability | Asked By Drew Murphy | Sep 18 12
11 Answers

Advice on Insulating Unvented Attic - 1884 Home in Zone 4A

I hesitate to ask a question on this topic knowing how many other threads exist. I hope my question is OK. I have spent considerable time on forums such as these and read many articles on sites like Building Science. I am struggling with making the right decision on the insulation.

In Energy efficiency and durability | Asked By Historical Work | Sep 15 12
5 Answers

Insulated Roof Questions

Hello All
I have a 1910 house, 1-3/4 story in Denver, CO (zone 5b) with an unfinished attic. The insulation on the attic floor needs to be increased. My roof is getting old and will need to be replaced soon as well. I’ve been reading about adding rigid insulation to the roof, which sounds appealing since the attic doesn’t cover the entire upstairs, but have a few questions:

In General questions | Asked By Patrick McNulty | Sep 11 12
4 Answers

Can Polyiso be applied in a remodel on the exterior of a building without creating moisture problems?

This is a house located in the mixed climate of Virginia. It is currently sheathed with OSB over 2x6 walls. The walls are R19 batts with paper vapor barrier to the warm side. Can the siding be removed, PolyISO applied, furring installed and new siding be installed without creating a mold and moisture nightmare. Removing all the drywall and applying a vapor barrier directly to the inside of the studs is not an option.

In Energy efficiency and durability | Asked By Rick Hyatt | Sep 18 12
1 Answer

Costs and performance characteristics for gas boilers and absorption chillers


I'm doing some research comparing various technology solutions for heating and cooling.

What I'm lacking is cost curves and performance characteristics for gas boilers and absorption chillers. I would like to have the costs and efficiencies for condensing and non-condensing gas boilers at, say, 50kW, 100kW, 200kW, 500kW and 1MW. And costs and efficiencies for single-effect absorption chillers at, say, a couple of hundred kW cooling capacity upwards.

I've found some data on gas boiler costs in some UK references but only for a small number of sizes.

In Mechanicals | Asked By David Coote | Sep 18 12
2 Answers

A little experiment with indirect HW heater

SO there was some discussion about the relative efficiency of indirect water heaters some time back.

It made me wonder, and I had the opportunity to check out the costs associated with standby losses in my system. The family was away for 28 days, so I could shut off the boiler, but that would be boring, so I decided to see how much energy it wasted creating no hot water.

The system:
Buderus GB125BE condensing oil boiler
Superstore SS 60 60 gallon tank

In Mechanicals | Asked By Keith Gustafson | Sep 17 12
2 Answers

Experience with carbon footprint modeling for construction?

Anyone have any experience using the Athena Institute Impact Estimator? I'd like to model alternative construction scenarios to see how much impact each has on reducing the carbon footprint of design elements, material and system choices. Need some help navigating the tool.

In GBA Pro help | Asked By Miki Cook | Sep 15 12
Register for a free account and join the conversation

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