polyethylene

Plastic Production Rises But Recycling Can’t Keep Up

Posted on March 03,2015 by ScottG in pet

Plastics serve many purposes, but millions of tons of discarded plastics end up buried in landfills, floating in the world's oceans, and burned in poorly regulated incinerators, a report from the Worldwatch Institute says.

Polyethylene Under Concrete Slabs

Posted on March 03,2015 by user-756436 in blotter sand

What goes under the concrete in a slab-on-grade home? In the old days, not much — just dirt. Eventually, contractors discovered that it made sense to include a 4-inch-thick layer of crushed stone under the concrete. The crushed stone provides a capillary break that reduces the amount of moisture flowing upward from the damp soil to the permeable concrete. Since the crushed stone layer provides a fairly uniform substrate, it also may also reduce the chance that a concrete slab will be poorly supported by random pockets of soft, easily compressible soil.

What Happens When You Put a Plastic Vapor Barrier in Your Wall?

Posted on March 03,2015 by ab3 in polyethylene

A lot of people have heard advice about vapor barriers and vapor retarders. Many of them have walked away confused. A big part of the problem, I think, is that they've been told what to do — "Put it on the warm-in-winter side," or "Never use one" — but they haven't had the physics of what happens explained to them.

Smart Vapor Retarders

Posted on March 03,2015 by AlexWilson in polyethylene

Nowhere in building design has there been more confusion or more dramatic change in recommended practice than with vapor retarders. Thirty years ago, we were told to always install a polyethylene (poly) vapor barrier on the warm side of the wall. Then we were told to forget the poly and go with an airtight layer of drywall (airtight drywall approach). Insulation contractors, meanwhile, often said to skip the vapor barrier; we need to let the wall or ceiling cavity dry out. It made for a lot of confusion. And I’m not sure we’re totally out of the woods yet.

How to Deal With a Vapor Barrier Edict

Posted on March 03,2015 by ScottG in MemBrain

Christopher Solar had a simple plan for an addition to his Ottawa home. The one-room structure would have a shed-style roof with a cathedral ceiling and vertical board siding. Solar liked a wall assembly he'd read about at GreenBuildingAdvisor, which consists of exterior foam, batt or blown insulation in the stud cavities and airtight drywall on the interior. An interior polyethylene vapor retarder never entered the picture. And that's where his story gets complicated.

Do I Need a Vapor Retarder?

Posted on March 03,2015 by user-756436 in perm

Every couple of weeks, someone sends me an e-mail with a description of a proposed wall assembly and an urgent question: “Do I need a vapor retarder?” Energy experts have been answering the same question, repeatedly, for at least thirty years. Of course, even though I sometimes sigh when I read this recurring question, it’s still a perfectly good question.

Vapor Barriers Redux

Posted on March 03,2015 by ScottG in Building Science

Few topics in building science seem to have caused as much confusion as the use of a polyethylene vapor barrier in exterior walls. Once routinely used by builders to prevent the migration of interior moisture into wall cavities, polyethylene is no longer recommended for houses unless they’re built in extremely cold climates.

Can Polyethylene Be Used as an Air Barrier?

Posted on March 03,2015 by ScottG in PERSIST

Polyethylene sheeting has had its ups and downs as a preferred building material over the last 20 years. At one time, it was routinely used in wall assemblies as a vapor barrier. As building scientists learned more about air and moisture movement through walls and ceilings, however, they began to advise builders that an interior vapor retarder is better than an interior vapor barrier, and the perceived usefulness of poly plummeted.

How Safe is PEX Tubing?

Posted on March 03,2015 by ScottG in bisphenol A

Builders have climbed on the PEX bandwagon in droves. Cross-linked polyethylene tubing is increasingly taking the place of copper in residential plumbing systems for a variety of reasons: ease of installation, resistance to acidic water, and the virtual elimination of leak-prone fittings. It all adds up to a juggernaut for a building material that's only been available in the U.S. since the 1980s. But Arlene DiMarino isn't sure about the safety of PEX.

New Green Building Products — September 2010

Posted on March 03,2015 by user-756436 in can light

In this new-product roundup, I'll look at a cover for recessed can lights, a new caulk for polyethylene, and several new water-resistive barriers (WRBs) that promise better performance than Tyvek or Typar. A fire-resistant hat for recessed can lights A Delaware manufacturer named Tenmat is selling an airtight hat for recessed can lights. Tenmat light covers are made from mineral wool; according to the manufacturer, they are fire-resistant.

Vapor Retarders and Vapor Barriers

Posted on March 03,2015 by user-756436 in polyethylene

Although building science has evolved rapidly over the last 40 years, one theme has remained constant: builders are still confused about vapor barriers. Any energy expert who fields questions from builders will tell you that, year after year, the same questions keep coming up: Does this wall need a vapor barrier? Will foam sheathing trap moisture in my wall? How do I convince my local building inspector that my walls don’t need interior poly?

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