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!


6 Answers

Critique this rough floorplan

We are in beginning stages of choosing an architect/project manager, but we have some wishes on how we want the floor plan to be.

Being amateurs, I'm sure there are mistakes. Please critique.

Our goals, wants and needs:

- make the house as small as possible, ut with enough room for everything we need/want
For example, we want a study, though that is not common practice here. We took that good practice from USA and like it a lot.

Asked By davor radman | Mar 28 17
5 Answers

Need sizing advice on a minisplit unit

I installed a Mitsubishi FH12NA in summer of 2014 when they first came out. I live in inland San Diego, and it can get hot, like 10-15 degrees hotter than the coast.

My condo is a studio and is only 420 sq ft. I'm on the upper unit of 2 stories. I face East and South. I have a skylight and dual-pane windows. Building is 1978 construction.

My Mitsubishi is weak. I set the temp and it will barely do anything. I have to set the temp to 61 and manually put the fan on high for it to do anything. Even "powerful" mode is weak.

Asked By aypues | Mar 16 17
23 Answers

Wall moisture monitoring

I'm diagnosing a tricky moisture issue. Part of the process has involved the use of wall cavity humidity and temperature probes. I have some data and I'd like to "peer review" some of the findings in broad strokes.

First off, this great article got me thinking:

http://www.greenbuildingadvisor.com/blogs/dept/musings/when-sunshine-dri...

Asked By Rob Simpson | Mar 6 17
0 Answers

Rigid foam over fiberglass wall batts in attic

I'm amazed at the info this site has. Hopefully someone can give me some insight on a couple of problems I have:

I have a two story home in Texas. In my garage attic, I have 60 x 10 feet of vertical walls facing the hot attic space. These walls are of 2x4 construction with vertical unfaced fiberglass batts held in place with a thin mesh.

1) The interior walls on the backsides of these attic walls are warmer to the touch than other walls in the room. There are many voids in the fiberglass batts and I can see the backsides of many of the outlet boxes.

Asked By Nigel Campbell | Mar 30 17
0 Answers

Rim joist with exterior EPS

My home has 1" of EPS on the exterior walls and covering the rim joist. The rim joists are uninsulated on the inside. If there was no exterior rigid I'd use a combo of rigid foam board and batts on this inside, but because of the exterior insulation, I'm concerned about creating a vapour sandwich.

Is the best approach here to air seal from the inside with caulk or canned foam, then add FG or roxul batts to allow inward drying?

Thanks,

Asked By ryan ryan | Mar 29 17
0 Answers

Floor Above Unconditioned Space

Hello
Firstly thanks for the feedback on my previous roof assembly post. This question relates to the floor of the conditioned area (ceiling of a garage/carport). Thankfully no ducts, just wires and plumbing in a few locations.
By way of background, its climate 4C (near Vancouver, Canada) and a small building used as a holiday home, not fully occupied in Winter. The occupied conditioned space will sit above both an unconditioned garage and cantilevered over a carport.
Designers build up from conditioned side down:
- ¾ OSB T&G
- Poly sheet
- 9.5” I Joists on 16” centers

Asked By Quinn Sievewright | Mar 29 17
8 Answers

Green & Passive design

As an architectural designer, I have long been interested in green and passive home design, having dabbled and dreamed. I now have a project that will encompass both, as well as the use of SIPs for roof and walls.
Simple questions with elusive answers:
1. Where can I find the angles of the sun at June 21 & Dec. 21 for a specific latitude?
2. How do a loft area and high vaulted ceilings fit in? It seems that both the Window to Wall ratios, and mechanical load numbers are all calculated using square footage. Surely ceiling height and volume have an impact.

Asked By Becky Nemetchek | Mar 29 17
5 Answers

Joist - Hard to Sister

A joist was cut, and I sistered it. However, the joist now is in the path of a toilet flange (which accounts for the original cut).

To get the additional joist to fit, I laid it on the two supporting walls nearly horizontally, and then used a series of clamps to get the board vertical, then bolted the joists together.

The other side of the wall has an open width of about 6 inches, and I was unable to fit the whole, additional joist in that space.

Asked By Erich Riesenberg | Mar 29 17
0 Answers

Energy Efficient Envelope advice

I'm building a high efficient cabin in climate 6 (dry) and have got a ton of helpful info from this site. I was hoping the the experts that frequent the site could make comments or give advice to improve the design. Also, let me know if there is something that doesn't mesh with the current building science. Any input would be helpful, thanks.

Foundation System:
Sealed crawl space with vapor barrier and 4” rigid foam insulating interior foundation walls.
Ground Floor System:
I joists with R30 batt insulation.
Above Grade Walls:

Asked By David Voros | Mar 29 17
5 Answers

Laminate floor underlayment in basement

I built up a basement floor with 3/4" OSB on 1.5" rigid foam over 6 mil poly on concrete slab (per this previous inquiry .http://www.greenbuildingadvisor.com/community/forum/energy-efficiency-and-durability/99205/insulation-basement-slab-question-polyethylene) .The difference this past winter was quite evident. Current question is what to use as underlay for laminate flooring. Some questions:
Should I use a permeable underlay so that the OSB is not encapsulated between the poly/foam layer below and an impervious "3 in 1" underlay above?
Or is conventional "3 in 1" underlay okay?

Asked By Grant Robinson | Mar 28 17
Register for a free account and join the conversation


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