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!


13 Answers

Mortar bridging and droppings

General question on Mortar Bridging and Dropping workmanship.(CZ4)

Here are a few images of some brick veneer on a house. Its not mine, but it is from the builder I will be using. I've read that droppings and bridging are "bad" but I don't know what constitutes good vs typical vs poor. So I've attached some pictures to get others viewpoint on the quality of this work. There is a single layer of tyvek and then OSB behind that, and I'd say ~1" of space behind the veneer, at least where there is not bridging.

Asked By Stephen Cook | Jun 16 18
1 Answer

Unorthodox foamless insulation system

I've been a long time reader and spent countless hours on BSC trying to learn all I can on building science. The biggest thing I've learned is how much I didn't know. Long story short...we have been making improvements to our home, some cosmetic and some as efficiency when they align. This winter our dated central air heat pump tried to catch on fire(long strory) and after a few months of research we successfully replaced it with three mini splits and they are fantastic! It was unplanned but extremely successful.

Asked By russell boudreau | Jun 19 18
0 Answers

Re-sealing failing SIP Roof Panels

We have a 7 year old SIP panel over a timber frame home. We have noticed for several years significant condensation of moisture to the point of dripping from light fixtures and ceiling fans located in the peaks during hot summer days. Roof is a stone-coated metal shingle panel over Grace Tru-flex underlayment. After many attempts to define the problem from our contractor/roofer and the SIP company we finally brought in our own professional. The verdict is that the SIPS at the ridelines were essentially not sealed.

Asked By passagyrs | Jun 19 18
10 Answers

Plumbing too close to edge of slab

A plumber set a vent pipe within a 1/4" of the edge of the slab on one of our jobs. When we told him to move it, he cried. I was surprised to find that this was not covered in our specification and I could not find it in code documentation. In fact, I could not find it anywhere. We have all seen concrete on the edge of a slab bust out around a vent stack or a piece of rebar that was too close to the edge of the slab.

So what is too close?

Asked By Hugh Stearns | Jun 18 18
5 Answers

Log home heat loss

I am currently working on a project that the homeowner has asked me to help size a replacement furnace for a log home. Currently the home is heated by an outdoor woodstove, which used 15 cord last year. The outdoor stove heats water which moves to a water to air exchanger in an LP gas forced air furnace. The gas is used only as emergency heat. I'm planning on conducting a blower door test. (Last log home blower door test I conducted was 19 ACH50!) There is some roof repair that needs to be completed, should be able to figure out the R-value in the roof at that time.

Asked By Randy Williams | Jun 19 18
7 Answers

Vapor permeance of thick foam sheathing and board seams

I have read that at a certain thickness, all foam boards (eps, xps, and polyiso) lose their vapor permeance, effectively rendering them vapor retarders with very low perm ratings. Does anyone have a link to the research behind these findings and if so can I be pointed in the right direction?

I am hopeful that the effective thickness at which this condition occurs for each foam is stated on the research but I will hold further questions till I have read up on it.

Asked By Sash057 | Jun 18 18
11 Answers

Anyone use Dennyfoil to block fumes from a renovation?

A Contractor is renovating two walls in my apartment near the windows. I’m very chemically sensitive. one suggestion is to place dennyfoil on the wall to block the fumes from coming into my apartment.

Has anyone used it successfully for this purpose and have any suggestions
On how to reduce the risk of mold growing. One person suggested applying the foil tightly to the wall using tape. To not use the air conditioning. And to consider getting a dehumidifier when it’s humid in my apartment.

She also recommended I consult with a building science expert. Any advice or feedback?

Asked By Daisy63 | Jun 5 18
6 Answers

Circulating air between floors

I don't see a lot of air mixing between floors in my (partly finished) house. We had a hot day here yesterday (34C / 93F), and by sunset the first floor was 22C / 72F while the upstairs was around 24.5C / 76F. This doesn't surprise me, as hot air obviously rises, plus the 1st floor has the benefit of the slab heat sink. What surprised me is that this morning the temperatures were the same. I would have thought with minimal heating going on during the night, they would have equalized at least somewhat.

Asked By Trevor Lambert | Jun 18 18
14 Answers

Dirty electric from minisplit ductless heat and air conditioning

I saw a u tube video on a Fujitsu mini split system air/heat...where a building biologist specialist was testing a persons house for dirty energy. He found from the box on the outside of the house had very high amount of electro magnetic interference... and determined that it came from a Fujitsu Mini Split system... he used filters to try to eliminate the energy...which worked for everything but the Fujitsu System. He said the spikes were the same type that causes occular melanoma cancer.

Asked By Arleendv | May 30 18
6 Answers

Building code requirements for stacked window headers, bracing, and stucco over foam

We are building in climate zone 5 and the county currently enforces the 2009 IBC & IRC.

We prepared a list of questions for our building inspector, some of which are location specific, but since we have gotten no response we figured some of this is probably common knowledge.

1. Do non-load bearing walls require structural headers?
2. Can vertically stacked windows of the same width share a header and king studs?

Asked By Zane Bridgers | Jun 17 18
Register for a free account and join the conversation


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