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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?

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.

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.

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?

Asked By Susan Larkins | Dec 14 14
2 Answers

Sprayfoam house and real stone cladding. Wall sheathing?

Good day,

This is my first post, but I want to comment how much I've enjoyed reading topics on this q&a forum.

My question is regarding a new house I'm building. Zone 8 climate (cold!) similar to Alaska, 2x6 framing 16" OC walls, 1/2" OSB sheathing, no basement. Right now I'm just finishing up framing.

I've been dead set on using closed cell spray foam all around...on the interior wall cavity at 3" thick, 4" on the roof deck and 1.5" on the floor.

Asked By Mark Helmrich | Dec 15 14
17 Answers

Sealing bottom plate to slab

My framer says that Sill Seal does not do a good job. I am inclined to agree with him. He is recommending a bead of liquid nails. I have been looking for real information. Certainly by now there have been some test run to measure the efficacy of various products and methods. And a new home slab is not a laboratory. How well does this or another product stick to a slab that has been wet and muddy?

Asked By Hugh Stearns | Aug 28 13
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)

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":

Asked By N Madrid | Dec 15 14
84 Answers

Modern (hydronic) heating and what all should start to know as of 2014

I stumbled upon this site to do with researching an update to a (hydronic) heating system I installed two decades ago.

So much has changed mainly the best change is the access we all have now to information.

This is the best read I have had off the internet to do with modern current (hydronic) heating.

Dana, besides your wealth of help here, this pictorial is great for the visual types like me.


Asked By aj builder, Upstate NY Zone 6a | Dec 4 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?

Asked By Kevin Peters | Dec 11 14
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