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!

6 Answers

Age-old question of insulation payback — only heating costs? Why not the costs of cooling?

I'm in lower NY state Zone 5 (just), I have R-38 batts in the ceiling and want to put plywood down after bringing insulation level up 6 inches (cellulose).

Now I've been looking all over Google for a payback calculator that handles both heating and cooling. I've seen the heating one on GBA. Or am I missing the fact that you don't need to worry about the cooling if you have heating?

Sorry if It seems like a trivial question, but trying to figure the payback but it seems strange to me I can only find a heating payback not one where cooling in involved.

Anyone's feedback is appreciated.

In Green building techniques | Asked By Darren Finch | May 14 12
1 Answer

"Metal shingles" vs "lifetime" asphalt

A local neighborhood's covenants forbids metal (standing seam) roofs. If I decide to build there, I'm looking for longevity and recycling and trying to anticipate life cylcle costs.

On the one hand, I'm thinking of the GAF Timberline "cool roof" asphalt shingle with a "limited lifetime" warranty. Locally prices run about $160/sq.

But I've also found these: "Stone Coated Metal Shingles." There are several mfgs online. But I haven't found local contractors who have used them or who know about them. They seem to run between $250 -- $300/sq.

In Green products and materials | Asked By JoeW N GA Zone 3A | May 14 12
1 Answer

Is it OK to use spray foam on the back of a plaster wall and then fill the stud bays with fiberglass?

First, a little background: I am a plumbing, heating, and cooling contractor in Wilmington, DE. I own a circa 1874 balloon-framed house.

I am in the planning stages of my renovations. The wood lath plaster walls are in great shape, so I do not want to tear them out. As I’m sure you all have deduced, my house has no insulation except in the attic.

In Energy efficiency and durability | Asked By Shawn Woodrow | May 14 12
2 Answers

How to seal a crawl space in new constuction?

My idea is to put down 10-mil poly before pouring the footings and run the poly into the footings.

Will moisture from the concrete walls be a problem? Is there a better way?

In Green building techniques | Asked By larry ogden | May 13 12
26 Answers

Using polyisocyanurate insulation on the exterior of a home

I just read one of the discussions’ on the use of polyisocyanurate insulation on the exterior of a home and how it acts as a vapor barrier and not to use it because it doesn't breath, thus resulting in potential condensation and mold problems within the walls. My concern is that I am currently getting ready to reside my house and I have already installed this on 50% of my home. I wanted to only add 1.5" thick foam to work with my 8" windows jams that I have upgraded to So I wanted the most R value possible from a foam. And polyiso gave this and It was also cheaper then the 2" XPS.

In General questions | Asked By Shane Kingston | Jul 3 11
24 Answers

Is a thin layer of rigid foam better or worse than nothing?

I am building near Madison, WI. Our house plan has walls that consist of (outside-in): Cedar or Hardieplank, tyvek, 7/16 OSB, 16" on center-studs, R23 bib insulation, 6 mil vapor barrier, drywall. My question is whether 0.5" of rigid foam insulation added to the exterior, inside the Tyvek will do more harm than good. I gather it will reduce thermal bridging, but it is too thin and may lead to moisture problems. I know 1.5 to 2" of rigid foam is the correct thickness. So the question is, should I just ditch the foam?

Thanks in advance.

In Energy efficiency and durability | Asked By Adam Bayliss | May 6 12
5 Answers

Heat loss and condensation through mechanical penetrations in the building envelope

A great deal of space here is dedicated to building air tight well insulated homes. This of course is good but what products can minimize the heat loss and vapor problems that arise from the penetrations in the building envelope by mechanicals? For instance how can a dryer vent be gasketed to an R of more than 1. Likewise how are the bathroom and kitchen vents handled to improve efficiency? Also concerning the dryer vent what is done with the moisture that can form when the moist warm exhausted air hits the cool outside air?

In Mechanicals | Asked By tom ruben | May 10 12
3 Answers

Indoor air quality

Hello GBA!

We are looking for solutions to help with the indoor air quality of our home. We live in the Minneapolis, MN area and have switched our home from forced air to a hydronic system. This was done to enable us to remodel our home to better suit our needs. Due to this change and the tighter envelope of our house, we are experiencing the typical condensation on our windows during the winter. Are there any ideas out there that may help us control the air quality inside our home?

Thanks for the help!

Mark and Melani

In GBA Pro help | Asked By Mark Bowser | May 12 12
27 Answers

Did an add-a-level, insulation options are of concern with solar panels

I have just completed an add-a-level on a New Jersey cape cod home and am at the point where I need to decide how to treat the insulation issue up there. I might add that there is a furnace up there in the attic with lots of ductwork which the installer wrapped. The south facing roof will be completely covered with solar panels. The existing insulation on the first floor is admittedly not the best, but short of ripping out all the walls there wasn't much I could do that I was aware of.

In Energy efficiency and durability | Asked By Monica | Feb 6 10
8 Answers

Mini-split, air circulation and noise transmission

We are considering using a mini-split system on our new tight home (double wall cellulose on a insulated slab) in Upstate NY (Zone 5a). We are both consultants with full time home offices.

One option is a hidden short ducted system on the first floor (1,500 sf) to duct air to the main living area and the master bedroom area and a regular mini-split unit for the upstairs (800 sf) where we will have our two offices, a bath, storage and a guest room. Our mechanical room is on the second floor. I don't want a visible unit on the first floor.

In Mechanicals | Asked By Elizabeth Kormos | May 10 12
Register for a free account and join the conversation

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