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!


1 Answer

Rebar splicing

I've seen footing rebar tied it two ways. One was the horizontal bar laying side to side at 24" overlaps. The other was horizontal bar facing top to bottom at 24" overlaps.

Which is the right or better way? The top to bottom seemed "cleaner" but not sure which is best?

In General questions | Asked By Peter L | Nov 23 16
1 Answer

Insulation options to add R-value

I had the opportunity to reroof this spring and add exterior rigid foam. I used foil faced polyiso 2.75" thick. Due to time and money constraints I applied a single layer taped and foamed. Through fastened wth .5" OSB cut into 3" strips. A new OSB deck was installed and asphalt shingle roof on top of that.

In Energy efficiency and durability | Asked By David Mosijchuk | Nov 23 16
74 Answers

Sun Bandit solar water heater

Hello. I was reading the article by Martin Holladay entitled "Solar Thermal is Really, Really Dead" and enjoyed the discussions going back and forth on the topic of solar water heating methods. I am planning on building a small 600sq' SIP cabin in the area of Nelson BC (climate zone 6) next year and I found this product listed as being one of the most efficient for heating domestic hot water on the Canada Energy Guide site. It says it can also be used for space heating via a radiant floor system or perhaps radiators.

http://www.sunbandit.us/

In Green products and materials | Asked By Scott Wilson | Oct 21 16
7 Answers

Mold in fiberglass insulation

I have a lookout basement, built in 2009 in climate zone 6, currently unfinished. The above grade framed section of the lookout wall is framed with 2x6s and insulated with fiberglass batts and a poly vapor barrier on the interior side of the wall covering the fiberglass. I have noticed small dark areas in the fiberglass throughout the wall where it meets the poly sheet. The dark spots are very sporadic and appear at first glance to be mold to me, although i have not confirmed this.

Assuming this is a mold issue, what would be the preferred method of replacing the insulation system?

In General questions | Asked By Nick Collins | Nov 23 16
3 Answers

Insulating a brick wall from the inside

Hi,

We have a 100 year old row house in Montreal, (zone 5000). Most walls abut the homes on either side, but we have a bump out in the back with two exposed walls. The walls are two bricks thick, (I think), with plaster on the inside, and I think a layer of drywall on top, (judging by how the walls are actually proud of the original baseboards).

The walls in question are in our bathroom, which gets quite chilly. I'd like to add foam board insulation on top of the walls, and then drywall on top of that again (we can live with the resulting deep sills in the windows).

In Green building techniques | Asked By Sean Lewkiw | Nov 23 16
10 Answers

Attic air barrier/vapor retarder

I'd like to get some feedback on this detail (attached). Background: <700 SF seasonal home in Climate Zone 6. 2x6 at 24" walls are insulated with dense pack cellulose. Rafters are 2x12s at 16"oc (snow country) and ceiling is 2x8 T&G douglas fir laid across 2x10 (actual) bottom chord ~44" apart which are exposed to the living area below. It is 1-1/2 story (just lower level and loft) and I am venting the roof. Heat is radiant slab from tankless boiler augmented with a wood stove when we are there (the only penetration in the ceiling besides the hatch, both sealed well).

In Green building techniques | Asked By Julie Brown | Nov 17 16
20 Answers

I’m remodeling a roof constructed from tongue-and-groove cedar planks that serve as a cathedral ceiling

I'm re-modeling a roof (~1:4 slope) constructed from 2.75" x 6" cedar planks (tongue & groove) that serve as a cathedral ceiling, structural support, and roof sheathing. (In Climate zone 5.) I have a tentative plan of adding 7.5" of polyiso sheet and then a metal roof.

The part of the house this roof covers is 24' x 28'. The roof has 4.5' overhangs on the north and south sides. The only penetrations are 1 vent fan, a light tube, and vent for water heater.

In Plans Review | Asked By Robert Hudson | Nov 13 16
4 Answers

Insulation for vaulted ceiling

We re-roofed our house this summer and found a lot of damage over our family room with a vaulted ceiling. We replaced the plywood and are now redoing the underside. The roof has a roof ridge vent and ventilation holes in the soffits. We are creating on-site baffles with 1" rigid foam boards. We are planning to use R30C insulation which is denser for cathedral ceilings. The question is do we use faced or unfaced, and do we need to use plastic sheeting as a vapor barrier? We want to get it right this time!
Thanks,
Kim

In GBA Pro help | Asked By Kim Howard | Nov 22 16
2 Answers

Questions on insulation and air sealing an attic (new construction)

Questions for all the great contributors to GBA: Building a new home in Zone 5, Philadelphia area.

Framing is done. Roof is finished. I was talking to the insulation sub, and he had some concerns.

My roof is a 4/12 pitch, that is now set up as a ventilated roof, and because of that in most places it's more of a crawl space then a walkable attic, and because of that I do not think it would be possible to add plywood as my air barrier in the attic before drywall and and can lights go in.

He recommends one of 2 options:

In General questions | Asked By Boris Rubinstein | Nov 22 16
3 Answers

Spare the Air days and mechanical ventilation: are filters or cutoffs recommended?

Our local air pollution control district is promoting awareness of days when air pollution is particularly onerous (in our area due to winter still air and wood burning fires). Has anyone analyzed the need for HRV air filters or temporarily turning off mechanical ventilators in these conditions?

In Mechanicals | Asked By Bill Fitler | Nov 21 16
Register for a free account and join the conversation


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