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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.

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?


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
9 Answers

What about installing a cooktop downdraft vent/ducting in a slab?

I have installed two cook top downdraft vent/ducting systems with great success but never in a slab. In this case the duct would be embedded in the concrete slab with exterior grill through the perimeter foundation and still above grade. What should I look out for, take into consideration?

There will also be a return from an HVR system in the Kitchen area. (Thanks to the excellent article by Martin I am in dialog with Zehnder)

In Mechanicals | Asked By Caroline Di Diego | Dec 14 14
3 Answers

Attic ventilation

The information available on your site is awesome, so thank you for making it available to others.

I'm located in 2A region, a coastal county in Texas. I recently purchased an approximately 1120 sq ft farmhouse built in the 1940's. The home currently has three turbines in peak areas, each within about 10 feet or less from a gable vent. There are no soffits; the roof hangs over about 8 inches (in most areas) and has about 2 -4 inches, ( most areas) above the top plate under the roof interior. The HVAC is in the attic space.

The house is basically a "T":

In General questions | Asked By N Madrid | Dec 15 14
8 Answers

To install engineered hardwood flooring over a basement slab, can I use (2) 3/8" CDX plywood over 1/2" XPS?

QUESTIONS: Can I use 2 layers 3/8” CDX Southern Pine plywood (joints staggered, glued & screwed together, but NOT mechanically attached to the slab) over 1/2" XPS? Whether I install the plywood sheathing over a vapor-retarder or rigid foam insulation, is CCA treated plywood necessary in either case? Which installation method (e.g. rigid foam or vapor-retarder) do you recommend in view of my concerns below?

In Energy efficiency and durability | Asked By Kevin Peters | Dec 11 14
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