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

+100-year-old house remodel: Flanged window installation & wall retrofit

Hello All,
I am remodeling a +100 year old house (located 2 hours south of Chicago, IL) and will be installing Andersen 200 Series Double Hung windows (6’x3’) that have vinyl nailing flanges.

Existing exterior wall construction from inside to out:
Plaster and shiplap (keyed to hold plaster) (both removed to add mineral wool insulation to stud cavity), 2x4 studs (original and new), horizontal lapped board siding, asphalt (or asbestos?) shingles, vinyl horizontal siding (removing to replace).

In General questions | Asked By Jane Campbell | Nov 7 15
3 Answers

Please advise: Polyiso exterior in mixed humid coastal climate

This site is wonderful...and I'm hoping I can get some of you to weigh in on the wall assembly we are designing for an upfit of a really old single wide trailer at the coast. I'm wondering about the polyiso and how warm humid air on the inside dries out during the winter.

##### Proposed Wall Assembly #####
Based on all our reading and research, here's what we're thinking for an exterior wall assembly.
* Interior finish: 1/4" plywood paneling, painted with non-vapor barrier paint, then

In General questions | Asked By Christy Shi Day | Nov 7 15
3 Answers

Spray foam and drainage space at sill pan cavity

Hello GBA,

The gap of the sloped sill pan and window was spray foamed to the back of window flange.

I've removed foam from some windows. Is it worth removing SPF from other windows and re-spraying with less foam.. or use backer rod/sealant for interior seal?

Or should I leave the rest like they are and have the blocked drainage gap.

I'm wondering if it is more important to insulate under window frame to improve performance of the outie windows.

In General questions | Asked By kyle lamont | Nov 7 15
6 Answers

Siga Corvum tape

hi all, i would like to trim the foam and apply corvum for additional airtightness. i got a little overzealous when flashing the window r.o.. should i cut the tyvek back to the same depth as the window so that the corvum would adhere directly to the window and osb? i realize if i do not cut the tyvek back i will be relying on the bond of the tyvek tape bonding the tyvek to the osb...

In General questions | Asked By erik olofsson | Mar 10 13
3 Answers

New approach to furnace sizing?

Here is something i just heard about, i wondered the expert's opinions, the page is gone so the internet archive version is linked


In Energy efficiency and durability | Asked By Alan B | Nov 7 15
38 Answers

Why is there condensation on the return ducts and mold in the attic as well 60% humidity throughout the home?

This home has since been remodeled, including all new metal duct work and insulation. The issue that we need to resolve is the high humidity in the house at about 60-65% even though the unit is running efficiently. There is quite a bit of condensation on the return ducts in the attic as well. We have had two reputable Heating and Cooling Contractors come to assess the situation to no avail. The owner attempted to contact the original Mechanical contractor, but has not been able to speak to anyone yet.

In GBA Pro help | Asked By Jimmy Miller | Sep 1 15
3 Answers

Best insulation for half-below / half-above finished basement?

hi all,

i've been reading through blogs and articles on this site and beyond (http://www.greenbuildingadvisor.com/blogs/dept/musings/how-insulate-base...), etc.

i have a basement that we are finishing for bedrooms and bathrooms. one wall is attached to our neighbor, 2 walls are 3 feet in-ground, and 1 wall opens at grade. we are installing an interior french drain, with which we planned to include a vertical vapor barrier to a 3' height (to grade).

In Energy efficiency and durability | Asked By Josh Millis | Nov 6 15
3 Answers

Insulating skylight frame

So we got our shingles replaced and took the opportunity to do a chainsaw retrofit and added 2 layers of 2" EPS with Neopor (Terrafoam Platinum) which we tied in to the existing 2" EPS on the exterior of the wall sheathing I installed two years ago. Also replaced was the enormous plexiglass dome skylight in our upstairs ensuite bathroom. I didn't think how we were going to insulate it at the time of installation however and am just trying to figure that out now.

In General questions | Asked By Zac McCormick | Nov 7 15
6 Answers

What to do with mineral wool excess insulation?

Hello all,

I special ordered a bunch of Owens Corning mineral wool insulation that is 16" x 47" x 7". I would say it is exactly the same as Roxull, however I am not for sure. I used it in my walls and now I have about 80 pieces of 16 inch wide x 47 inches tall by 7 inches thick left over. I also have probably 150 pieces from my wall studs that are 1.5" thick shavings. I was originally going to fur out my walls 1.5 inches so the 7 inch thick piece of insulation would fit right in. However things changed and I did not end up doing that, the result is a bunch of leftover shavings.

In Green products and materials | Asked By Nicholas C | Nov 7 15
7 Answers

Cutting really thick EPS foam

I have a job coming up where there is going to be 8" of foam under slab.
The foam will be glued at the joints.
Over the years I have cut foam a number of different ways with varying levels of success.

I have used Tajima knives, circular saw, sawzall, handsaw, sharpened putty knives, table saw.

All of them worked ok, none great.

In Green building techniques | Asked By Colin Lindberg | Oct 28 15
Register for a free account and join the conversation

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