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!


7 Answers

Housewrap under vinyl siding

Ok, I'm getting educated and made some decisions. To recap, I'm residing with vinyl after stripping down to plywood sheathing (1/2" plywood over 2x4 studs, fiberglass batt, poly vapor barrier, sheetrock, zone 5). I've decided to go with 3/4" rigid foam over the plywood and under the vinyl which is R3 and very water vapor permeable. Can only fit 3/4" thickness insulation board (long story). Probably going to use Progressive Foam HalfBack H2O with water management system (grooves toward sheathing to drain any leaked in water). Want to add house wrap (Tyvek or Typar).

In General questions | Asked By george baloga | Dec 17 14
29 Answers

Any experience with an unheated (but insulated) slab as a finished floor? Will it be uncomfortably cold?

We are building a 1000 s.f. single-story home in Northwestern Ontario (climate zone 7) on a very tight budget. It will be well-insulated (walls R-40, roof R-60), and have triple-glazed windows, etc. An energy efficiency consultant calculated our heat loss as 16,800 Btu/hr at -32.8 F. The foundation is a short ICF stem wall with a 4" concrete slab (R-20 insulation underneath). Heating will be accomplished with the combination of a high-efficiency woodstove and electric baseboard, and we might add a mini-split down the road.

In General questions | Asked By Beth Turner | Dec 11 14
38 Answers

Heating with modulating condensing units

So far my looking into the use of a modulating condensing unit has left me with
the following;

They are high tech
They cost more than some older tech
They need good water with proper hardness and PH
They need a tech that is trained to maintain them
They do not condense if the return water is above 125 degrees.
Many install set ups include primary, secondary and what I call tertiary loops which to me add cost.

I can't understand how we go from $1000 to heat water to $8000 for all the parts for a fairly basic

In Mechanicals | Asked By aj builder, Upstate NY Zone 6a | Dec 15 14
7 Answers

Flow control valves for radiant floor heating

I have high efficiency house in central Vermont. It has radiant tubing in the floor for heat. I am trying to get the on demand hot water heater, a Takagi, and the circulator pumps to run as little as possible. Electricity is the biggest obstacle. The house is off grid with PV and batteries. Both are a little on the small side. The house has 6 zones with flow valves on each. No zone is over 400 feet. Tubing is 1/2 inch PEX. Current Delta T when three or more zones are open is 10 degrees. I currently have all flow valves wide open.

In Mechanicals | Asked By Jon Olson | Dec 16 14
6 Answers

Has GBA ever tested polyester fiber insulation made from clothing?

Has GBA ever tested polyester fiber insulation made from clothing? If so, what were the results and who makes it in North America?

Apparently, there is a huge push to use PET from recycled plastic bottles but little push to use recycled poly fabric. Some 75 to 80 % of Pet is used in fabric and it is largely going to landfills.

In General questions | Asked By Brian Timlick | Dec 16 14
4 Answers

Is Advantech better than plywood for subflooring?

My block and beam 1940's house had original tongue and groove 3/4 " pinewood floors in the original rooms of the house. This was the only floor. I've been checking around, and the best advice I've received is to use 3/4 Advantech over the original floors, before laying new 3/4" hardwoods. I believe this to be good advice, but is Advantech needed over regular plywood? And is 3/4" plywood needed over 1/2" plywood?

Thanks for any input.
NM

In Energy efficiency and durability | Asked By N Madrid | Dec 15 14
2 Answers

Is Roxul or EPS more environmentally friendly overall?

I certainly like that Roxul has high recycled content, but this PDF published by Roxul makes it look like EPS actually has a lower Lifetime GWP / sq. ft x R. Wouldn't that make it a better choice in the long run?

http://www.roxul.com/files/RX-NA_EN/pdf/Brochures%20and%20Sell%20Sheets/...

The document shows Roxul = 0.0455 and EPS = 0.036.
In addition they are comparing to a 1 pound EPS that only has R3.9 per inch.
If I am using Foam Control 2 pound Type IX the R value is listed at 4.35 per inch (75 degrees F.)
Would that be an even lower Lifetime GWP?

In Green products and materials | Asked By Marc Sloot | Dec 12 14
2 Answers

Cost analysis of thermal bridging in zone 2

Adding an addition to the house. 2x6 at 24". About 60 feet of wall. Cedar shingle siding. Concerned about the cost of installing ridged foam to prevent thermal bridging. Will the energy cost savings ever provide a return on the additional foam, horizontal battens at 5", labor, etc.

In Energy efficiency and durability | Asked By Robert Brown | Dec 15 14
14 Answers

Flat roof insulation

I have built an extension to my house with flat roof, continuation of the existing house. The rafters are 16 in apart and there is 6 in left for the insulation under the sheeting. The plans are requiring R30 insulation and the building inspector requested hard foam Thermasheath- 3, 5 in thick, leaving 1 in for breathing. The drywall was not installed yet, when water from condensation came down all over the place. There are vents on both sides of the roof, in each bay under the insulation level, not allowing the hot air to escape.

In Energy efficiency and durability | Asked By Angela M | Nov 22 13
10 Answers

Humidifier with a flash-and-batt house?

Hello. We are building a house in Virginia and the construction of the exterior wall is: Hardiplank, Tyvek, OSB, 1 inch closed cell spray foam, kraft faced R19 batt, and Drywall.

Our HVAC contractor is not installing the humidifier as he says tight homes don't need them. His comment was we might be calling him to install a Dehumidifier in all probability.

Is that true?

In Energy efficiency and durability | Asked By Susan Larkins | Dec 14 14
Register for a free account and join the conversation


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