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!


4 Answers

Moisture problems with vapor barrier - Part 1

I am a home owner building a 2,000 sq ft addition to our home 50 mls. north of NYC, on a small mountain in the Hudson Valley, so it's colder up here in the winter and less humid than the river valley in the summer. This is a wood frame two story structure without central AC built on an exposed concrete slab floor. We are at finished rough-in stage. This winter, the radiant heat in the slab was first turned on, resulting in a lot of moisture being evaporated from the concrete into the building.

In GBA Pro help | Asked By Tony Moore | Mar 18 12
3 Answers

Potential Difficulties with Roof Design

We are in the final design phase of our super insulated home and need some advice. The difficulty is with the eastern side of the house(entrance way) keeping in mind that an in-law apt. will be added in the future. The two final designs are attached. One with a flat roof porch and one with a high porch roof with beam supports.
The Problem: We prefer the high roof design but have concerns in two areas:

In General questions | Asked By rebecca Surprenant | Mar 18 12
12 Answers

I live in Northern Virginia. I am trying to resolve a dispute between my insulation contractor and the city engineer.

I plan on having open cell spray foam installed in the rafters of the top level of my home.

Dispute Details:
- The city engineer stated that I need to install a ridge vent and baffles that run the entire length of the roof from the ridge vent to the soffit vents. Then once inspected and approved, I can have the spray foam contractor spray the insulation over the baffles.

- The Contractor states that the engineer does not understand the technology and the the
spray foam should go directly against the sheathing.

In Building Code Questions | Asked By John Horton | Mar 15 12
22 Answers

Building a fixed-pane window into foam

I'm spinning this off from one of the many triple-pane threads rather than derailing it with my question.

Keith Gustafson wrote:

They get better:
http://www.cardinalcorp.com/technology/reference/loe-performance-stats/
I believe that the 1 1/8 triples are their thickest standard, as they did not want to go higher.As it is the ones that I selected end up with a U of .13, [R 7.7] COG.

In General questions | Asked By Minneapolis Disaster, 6B | Sep 24 11
6 Answers

Open Cell Spray Foam---Bubble Repair

I'm building a new 1 1/2 story home in a HH climate (2B). Insulation is ocspf---6" in walls and roof (i.e. semi-conditioned attic).

The insulation is complete, but there are just a few small areas that aren't well done. There are some areas (corners mostly) that have fist-sized holes in the insulation. It appears that there is enough foam to seal to the outside, but not full thickness because of a bubble. The contractor and the manufacturer both advised that I should just fill these up with canned window foam.

SO HERE'S THE QUESTIONS----

In Energy efficiency and durability | Asked By john walls | Mar 16 12
1 Answer

Do you have to mechanically ventilate an attic space used for storage?

Do you have to mechanically ventilate an attic space used for storage when the whole attic is within the thermal envelope? The roof is 10 inch SIP panels (R-60) and all walls are open-cell SPF.

The owners have asked if there is a code issue here. We can't find anything definitive.

In Building Code Questions | Asked By Ann Lathrop | Mar 16 12
4 Answers

In zone 4A, would I be OK to put 1.5" of closed SPF under my roof deck with unfaced R-38 below that?

I have 2x8 rafters, and they are furred down with 2x4's and there is a 1" gap as a thermal break between them. I want to foam the rafters entirely as well as the underside of the roof deck. I would use .5" sheetrock as an air and thermal barrier below the furring and batt insulation. I know code calls for R-15 air-impermeable foam, but with this set-up in southern, coastal Virginia would this be OK?

In Energy efficiency and durability | Asked By Matt Black | Mar 14 12
9 Answers

Site-built SIP panel — What foam to use?

I previously posted a question about the wall section in an addition where the added guest bedroom and bathroom were going to double as storm rooms. But I'll be danged if I can get back to that thread.

Anyway, on the exterior side of the studs, I was going to sheath with 3/4" Advantech subflooring, then add 1-1/2" of foam, then another layer of 3/4" Advantech.

I seem to remember that extruded polystyrene (blue or pink foam) will shrink with age, and, in fact I have observed this in my crawl space.

In Energy efficiency and durability | Asked By Bill Daugherty | Mar 14 12
3 Answers

Slimmest Blown Cellulose Insulation Cavity?

Hello,
Another question here. Hoping someone from the insulation community can give me an answer.

What is the slimmest insulation cavity that can be blown? Is it possible to blow 1.5" to 1.75" thick cavities? It seems like you could...you would just have to have a hose that was small enough right?

In Energy efficiency and durability | Asked By Spencer Burnfield | Mar 14 12
20 Answers

Abridged Version of Manual J 8th Addition Excel Program & MANY other questions

I am working on trying to do some sort of reliable energy modeling/comparison for a house that I am designing (and for future projects). I was trying to find out a few things: the difference in energy use between a standard 2x6 wall & a double stud wall, good windows & code, Code 2x6 construction/insulation levels & a better insulated shell with good windows (U-value between .20-.24, Floors R-38 to R-42, Whole Wall R-24+- & thermal break, Ceiling R-60). I downloaded a number of programs and they all seemed very tedious, had a tendency to crash, and seemed very difficult to use.

In Energy efficiency and durability | Asked By Spencer Burnfield | Mar 13 12
Register for a free account and join the conversation


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