Slab

How to Build Efficiently in Massachusetts

Posted on April 01,2015 by ScottG in double stud walls

Noah Kaput and his wife seem to be off to a good start in planning their 2,100-sq. ft. house in Massachusetts.

How to Insulate a Slab Foundation—With Straw-Bales?

Posted on April 01,2015 by ScottG in New construction

Superinsulated houses need insulation under the slab as well as in the walls and roof, and the most common choice for sub-slab insulation is rigid foam.

Deep Energy Retrofit: Focus on the Envelope

Posted on April 01,2015 by ChrisBriley in Green Architects Lounge

This is part two of the Green Architects' Lounge three-part series on deep energy retrofits. In this episode, Phil and I discuss what we believe is the most crucial part of a DER: the exterior building envelope. There is no single solution. Here, we must be nimble and thoughtful, and deal with the structure that we're given and apply the skills we've learned (and by we, I mean all of you listeners as well).

Green Basics Slab Foundations

Insulate the perimeter of all concrete slabs

Posted on April 01,2015 by Peterbilt in Kitchen or bath addition

**Before pouring a concrete slab, install rigid foam insulation along its perimeter.** If the slab isn't isolated by foam, there will be a thermal bridge to the foundation or soil. This makes the edge of the slab cold, compromising energy efficiency and possibly raising the temperature of the slab perimeter above the due point. This could cause condensation and mold growth. The insulation should separate the slab perimeter from all exterior foundation walls, footings, or soil.

Insulate beneath concrete slabs regardless of climate

Posted on April 01,2015 by Peterbilt in Kitchen or bath addition

**Use 2-in. of XPS (R-10) in all but the warmest climates** When detailing a concrete slab on grade, add insulation at the perimeter and beneath the slab. This is useful even in warm, humid climates. Here, insulation beneath the slab isolates the living space from cool below-grade temperatures. This reduces the chance that warm, humid air will condense on cool concrete floors. In Florida and the southern-most parts of Texas, Louisiana, Alabama, and Georgia you could drop back to 1-in. or R-5.

Use a frost-protected shallow foundation

Posted on April 01,2015 by Peterbilt in Kitchen or bath addition

**A frost-protected shallow foundation allows foundations as shallow as 16 in. (0.4 meters) in the most severe American climates.** Insulation, strategically placed around the foundation, raises the frost depth around a building. Since the late 1970s in Scandinavia, more than 1 million homes have used this technique successfully. This type of foundation reduces concrete use and excavation.

Build foundation walls with insulated concrete forms

Posted on April 01,2015 by Peterbilt in Kitchen or bath addition

**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 biodegradable form-release agents

Posted on April 01,2015 by Peterbilt in Kitchen or bath addition

**Release agents made with vegetable oil are safer**

Use fly ash in concrete

Posted on April 01,2015 by Peterbilt in Kitchen or bath addition

**Fly ash 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.

Keep soil gases out of the house

Posted on April 01,2015 by Peterbilt in Kitchen or bath addition

**Detail the house to keep unhealthful gases safely at bay.** Preventing soil gases such as methane, petroleum products, pesticides, moisture, and radon from entering the structure requires a two-step strategy. Make the foundation as tight as reasonably possible, and make it easy to vent the layer of soil beneath the building by depressurizing it. These steps also help keep water out of the foundation. It is easier and less expensive to install a vent from the area beneath the slab during construction rather than after the house is finished.

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