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

Closed cell foam in in vented roof

I have been able to avoid using spray foam up until now but with recent code changes in our area we are now forced to use it.

On a current job we are framing a new roof directly on top of the existing old roof sheathing because the owner wants to expose the hand hew beams of the original frame below. The new rafters are 2x8 and the plan is to spray the bays with closed cell foam on a warm day and then immediately sheath and roof.

I’m a concerned because the rafters will have no time to dry out before being foamed and I'm concerned about lumber shrinkage

In Energy efficiency and durability | Asked By Judson Aley | Nov 8 17
4 Answers

Air Sealing Question

When we built our garage/apartment, we sealed the perimeter of every stud bay to the Zip System sheathing panels with Tremco acoustical sealant. We also caulked or foamed every joint and space between the framing members, around windows, doors, header and top plates, etc. It was a lot of work, but along with the other air sealing details, it seems to have resulted in a VERY airtight structure.

One thing we did NOT do was to caulk the drywall to the wall studs, as we were not in town when the drywall was installed.

In Energy efficiency and durability | Asked By Nancy Broadbear | Nov 8 17
5 Answers

Why does insulation have to contact six sides?

On the internet I've read about 15 years worth of claims that insulation must contact all six sides for it to be effective, but haven't seen an explanation why. Yes, I've read many times that a building's insulation and air barrier must completely surround the conditioned space and be in contact with each other, but can't find the science behind it explained. I would sure appreciate a scientific explanation from anybody. Thanks very sincerely.

In GBA Pro help | Asked By JeffSch1 | Nov 8 17
1 Answer

EPDM Gasketed Joints vs Cement "Welded" PVC Joints for Flue Gases

I'm interested in warranty/service life of EPDM gasketed joints (in PVC or polypropylene) vs that of PVC cemented (chemically welded) joints. Am installing a furnace and would like to use polypropylene for the combustion air/vent pipes 'cause in many environmental impact categories the material itself is superior to PVC. Further, I guess I believe PVC bought at a big-box store by my HVAC contractor might not be designed specifically for HVAC venting.

In Green products and materials | Asked By Gordon B | Nov 8 17
2 Answers

MidAmerican Energy - dismantling energy efficiency program

MidAmerican is an investor owned utility owned by Berkshire Hathway/Warren Buffett serving several midwest states.

MidAmerican recently filed its proposal for a state mandated energy efficiency program in the state of Iowa. Nice glossy brochure, but the last page reveals its proposal to reduce the budget for energy efficiency by 40%, from $116 million to $71 million.

Last night, the company's director of energy efficiency met with a local group to answer questions. I am not an expert but have read GBA for several years and highly retrofitted my own house. A few main points.

In Energy efficiency and durability | Asked By Erich Riesenberg | Nov 8 17
9 Answers

Blower door is 250 cfm less with Radon mitigation on vs off. Why????

Appreciate all the bright minds on here who have helped solve "mysteries" with my home. I have another problem hoping to get some ideas on. Blower door diagnostics were done both with and without my radon fan/system running. Radon fan is on home exterior with pipes running underneath 12 mil vapor barrier in conditioned and sealed crawl). We had previously experience significant humidity in crawl space while radon fan was operating. Now ( thanks to the help of everyone on here) we have corrected that problem and the crawl space now stays pretty constant.

In General questions | Asked By hotandhumid | Nov 7 17
1 Answer

Most efficient oil heat solution

Need some help regarding best solution for oil-fired heating for my situation.

Here's my situation:

Live in NJ. Been in this house for a year, and plan to stay here for a LONG time. Heat exchanger on old oil-fired furnace is cracked. Had an independent manual J done, and the heating load is 77K Btu. Current heating system is one zone for the entire house (3200 sqft). It worked well enough last year that I'd stick with one zone if that's the best way to go given my design goals below.

In Mechanicals | Asked By Matt Culik | Nov 8 17
0 Answers

Vapro Shield

Does anybody have any experience with vaproshield products. In particular Wrapshield SA and Wrapshield RS. Any thoughts on cost effectiveness of SA vs. Zip per sqft?

In Green products and materials | Asked By Tim L | Nov 7 17
6 Answers

Best Ridge Vent for a Metal Roof

For Classic Rib (exposed fastener) steel panels on a simple 4:12 gable roof with a 14" universal steel ridge cap that simply covers the ridge, what ridge vent product do you recommend to keep bugs, etc. from getting in? The following seem to be the best options I've found, but I can't find enough reviews on them to give me any guidance. (I tried to make these links, but the forum interface wouldn't accept them.) In order of lowest to highest cost (on a tight budget).

SV2 Vent Foam

Marco Industries, Flex-O-Vent Ridge Vent

In General questions | Asked By Jeff Cooper | Nov 3 17
1 Answer

insulation of floor of house build on helicoidal piers


I built a house that is supported by helicoidal piers. I need to insulate the floor and would like to know what is best practice and what it is to avoid.

Some told me to insulate the cavity with fiberglass batt that touch the underside of the floor (higher position) and secure those batts in place and then close the system with sheating. I can probably put some fiberglass batt than XPS and then sheating.

In Energy efficiency and durability | Asked By PIERRE LEVASSEUR | Nov 7 17
Register for a free account and join the conversation

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