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!

9 Answers

Do I need to insulate a shared wall in the attic of my condo?

Hi Everyone!

I'm in central Mississippi (Zone 3). I have an unconditioned attic.

I have finished air sealing my attic. I cleaned out the ridge/soffit vents then placed preformed channels so that the ventilation in my attic is appropriate. I have also repaired, sealed and insulated the HVAC ducts in my unconditioned attic (yes I know). I am getting prepared to bring the insulation up to its proper level with loose fill blown in. Currently I have 4 inches of rock wool (put in back in 1973).

In Energy efficiency and durability | Asked By Luke Savoie | Mar 16 15
8 Answers

Why are these wires putting burn marks on paper-backed batts?

I've seen two houses in the past couple of weeks where wiring is leaving burn marks on paper-backed batts (see pics). I found these because I was snooping around looking for air leaks. I've always been told that insulating around wiring is fine if it's modern Romex type wiring, and that knob and tube is the only thing to watch out for. So finding these two examples is pretty terrifying.

In General questions | Asked By Peter Rogers | Mar 15 15
4 Answers

9 Foot walls with 8 foot XPS

Hopefully an easy question, but one that has been racking my brain. We are in Salt Lake City, Utah, zone 5B. 9 ft walls in my unfinished basement, poured concrete. Only about 1 foot is above ground level all around. I want to install 1" or 2" XPS on the wall, then stud wall in front of that with batt insulation. I can only find 8 ft tall XPS in any thickness. So far no one is willing to order in 9 ft.

Should I tape/seal the 1 foot section on the top or the bottom of the wall?

Will it make any difference in the end?

In Energy efficiency and durability | Asked By John Reid | Mar 15 15
14 Answers

Dense pack cellulose OVER closed cell foam in cathedral ceiling?

I am considering the following roof assembly in climate zone 4a: Will i run into code or condensation issues?

Single plane roof 3/ 12 pitch

1) 6x10 timber rafters 4' OC
2) 2x6 T&G decking perpendicular to and OVER (not pieced in between as a cosmetic ceiling) 6x10 rafters
3) 2x4 sleepers, 4' OC, parallel to 6x10 rafters on top of T& G decking.
4) 2x10 boards perpendicular to and resting on top of 2x4 sleepers, 2' OC.

In Building Code Questions | Asked By Daniel Miller | Mar 15 15
9 Answers

Another question regarding "Monitoring Moisture Levels in Double-Stud Walls"

So after reading Monitoring Moisture Levels in Double Stud Walls... I am in search of a solution for our double stud walls that are just about ready for insulation. We were planning on filling the 12" cavity with blown cellulose. But that has obvious and now understood issues with moisture and settling we didn't know about. So what to do with my walls? Our insulator suggests closed cell applied 4" R 28 and dense pack cellulose 8" R 28.8. This will still result in a plywood that gets wet and dries but at least we will know the dew point stay on the outside , right ? Thoughts ?


In Energy efficiency and durability | Asked By Jocelyn Smith | Mar 15 15
2 Answers

Can I waterproof a concrete deck/roof with either of these strategies?

I have an exposed concrete front porch. The porch also is the roof for a storage room located underneath. Because of a builder error, a waterproof membrane was not installed under the concrete and tied into the exterior drain plain. As a consequence, water always intrudes into the basement (conditioned space). (Before anyone asks, the builder will not honor his warranty and suing him is not a practical.)

I've researched several options for fixing this issue short of breaking up the concrete and starting over. The two most promising (and affordable) approaches are as follows:

In Green building techniques | Asked By Steve Knapp | Mar 16 15
3 Answers

Combine 2 bath exhaust fan runs to vent outside?

I have 2 bathrooms, each with a fan. Both come into the attic as flexible metal about 3 feet from each other. They then snake around and go down to a soffit.

I realize from reaching on this site that this isn't ideal. I'm considering switching them to rigid metal or pvc once they reach the attic, have each continue up slightly about a foot above the attic floor, then slope down toward a new vent in a gable wall.

In Building Code Questions | Asked By Jeremy M | Mar 15 15
5 Answers

Air sealing/insulation on top of stairs in a bungalow

Planning my air sealing project I'm most stumped by the stairs area. I tried some photos but they don't help explain it. I've attached one of the second floor hall, the stairs top out just to the left, I'm talking about the narrow ceiling showing in the photo and the slant on top of the ceiling over the stairs.

In Green building techniques | Asked By Jeremy M | Mar 13 15
2 Answers

Insulating and heating barn

We are are about to start on a project of converting our horse barn into an office area. We are in southern Coos County NH. The area we want to heat is 900 sf, so first floor only. Half the barn has a four foot crawlspace the other is full basement. The building is post and beam about 160 years old. The walls are 6 inches deep the floors and ceilings are thicker because of the beam construction. There is no natural gas, so propane Rinnai wall furnace is what we were considering for heat. Our plan was to use closed cell urethane for insulation, but are open to other ideas.

In General questions | Asked By Ken Chester | Mar 15 15
2 Answers

Is there a humidity calculator out there?

I live in a leaky house, the inside humidity tracks the outdoor humidity with a lag and temperature adjusted, but i want to be able to input an outdoor temp and humidity and calculate what the indoor humidity will eventually become at 20ºC (theoretically of course).

Basically i want to know what the resulting humidity would be at an input temp and humidity if that air was raised to 20C

I know the outdoor will eventually change before the indoor catches up but it would be useful to me.

In General questions | Asked By Alan B | Mar 15 15
Register for a free account and join the conversation

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