Retrofit for Radon Vent

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What’s Wrong With This Crawl Space?

Readers are invited to spot all of the problems shown in a photo of an old crawl space

Posted on Dec 26 2011 by Garrett Mosiman

The photo shows an unvented crawl space in a cold climate. The home was built in 1885. This crawl space is attached to an adjacent concrete-floored basement. The foundation walls are made of mortared limestone.

Even in the small area captured in the photo, there are a number of problems that compromise energy efficiency, building durability, and life safety.

Next week, we will post the answers that a Building America team, NorthernStar, came up with.

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Well, They Got It Half Right

What's Best For a Crawl Space — Fiberglass Batts or Rigid Foam?

Posted on Jan 22 2009 by Martin Holladay

At the International Builder’s Show, several demonstration homes have been set up in the parking lot outside the Las Vegas convention center.

The Environments for Living show home has a display promoting the advantages of ventless conditioned crawl spaces; so far, so good. But instead of following best-practice advice and insulating the crawl space walls with rigid foam, the Environments for Living home designers chose to install fiberglass batts between the floor joists — a feature proudly displayed behind a Plexiglas viewing panel.

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Image Credits:

  1. Martin Holladay

Crawl Spaces

Crawl Spaces: The Downsides of Basements With Few of The Benefits

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Image Credits:

  1. Chuck Lockhart
  2. Daniel Morrison
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Build foundation walls with insulated concrete forms

Structure and insulation in a single package
Unlike traditional concrete forms, which are removed after the concrete has cured, insulated concrete forms (ICFs) remain in place, providing foundation insulation. ICFs are hollow blocks made from rigid foam insulation or recycled wood fibers. Voids are filled with steel reinforcing bar and concrete.

Use fly ash in concrete

Fly ashFine particulates consisting primarily of silica, alumina, and iron that are collected from flue gases during coal combustion. Flyash is employed as a substitute for some of the portland cement used in the making of concrete, producing a denser, stronger, and slower-setting material while eliminating a portion of the energy-intensive cement required. More info can replace some of the Portland cement in a concrete mix
Manufacturing Portland cement uses a lot of energy and produces about 6% of the world’s carbon dioxide emissions. Replacing the 12% Portland cement mix in concrete with 15% to 25% Type C or Type F fly ash are fairly common, and mixes up to 60% are sometimes used. Contact your local Department of Transportation for advice about mixtures they've tested; this will help when talking to your building inspector and concrete contractor.

Use concrete block made with recycled material

Recycling industrial byproducts saves space in local landfills
Concrete masonry units (CMUs), also known as concrete blocks, that contain a variety of industrial byproducts are now available. Recycled material includes slag, cinders or bottom ash, and ground waste glass and concrete. Using this kind of block means less mining and crushing of stone as well as reduced load on landfills. However, most plants that make block don't publicize their formulas, so it may take some digging to find out what materials are being used.

Reuse lumber from concrete forms

Form lumber can be used for framing or outbuildings
There's no need to waste lumber used to make concrete forms. Putting it to another use reduces construction waste. Forms should be well coated with low-VOCVolatile organic compound. An organic compound that evaporates readily into the atmosphere; as defined by the U.S. Environmental Protection Agency, VOCs are organic compounds that volatize and then become involved in photochemical smog production. form-release oil, or protected by polyethylene to keep it free of concrete and easier to use later.

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