The most recent blogs at Green Building Advisor

Polyethylene Under Concrete Slabs

Posted on July 4, 2014 by Martin Holladay, GBA Advisor in Musings of an Energy Nerd

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 capillaryForces that lift water or pull it through porous materials, such as concrete. The tendency of a material to wick water due to the surface tension of the water molecules. 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.

Air Leaks From Your Home To Your Attic Need To Be Sealed

Posted on July 3, 2014 by A. Tamasin Sterner in Guest Blogs

It’s important to keep attic air out of the house and house air out of the attic. That's why the home performance industry and every above-code building program make it a top priority to fully separate attics from the rest of the building.

When the attic isn’t fully air sealed from the living space and the combustion appliance zone, three undesirable scenarios can occur:

A Blower Door Is the Hydraulic Jack of Building Science

Posted on July 2, 2014 by Allison A. Bailes III, PhD, GBA Advisor in Building Science

Remember the first time you ran a blower door? OK, maybe that's not the best way to get where I'm going because most first-timers turn the pressure up like they're practicing tai chi on Jupiter. After you've done a few tests, though, you learn to crank it up to 50 Pascals of pressure difference in just a few seconds. And that's where you may have discovered the mystery that Blaise Pascal solved nearly four centuries ago when he invented the hydraulic press.

A House For Slow Living

Posted on July 1, 2014 by Robert Swinburne in Guest Blogs

The original concept for the house I am working on came to me in a dream (yes – I dream architecturally). I think the dream may have been generated by the image on the right, which has been on my bulletin board for a few years.

My original sketch was called “a house for food.”

Looking for the Best Minisplit Option

Posted on June 30, 2014 by Scott Gibson in Q&A Spotlight

Ductless minisplit heat pumps have gotten many favorable reviews at Green Building Advisor, but Roy Goodwin sums up a concern that's popped up more than once: Despite their virtuoso heating and cooling performance, they're a little on the homely side.

Banish These Details From Your Plans

Posted on June 27, 2014 by Martin Holladay, GBA Advisor in Musings of an Energy Nerd

Is it possible to disassemble old shipping pallets and glue the pieces of lumber together to make furniture? Of course it’s possible; some woodworkers have used this method to make beautiful tables and chairs. There’s a fly in the ointment, however: while it’s possible, it’s not very easy.

Many commonly used construction methods, design details, and materials fall into a category I would call “possible but not easy.” I decided to create a list of items that fall into this category.

Part 4 of GBA’s Passivhaus Video Series

Posted on June 26, 2014 by GBA Team in Green Building Blog

At the PassivhausA residential building construction standard requiring very low levels of air leakage, very high levels of insulation, and windows with a very low U-factor. Developed in the early 1990s by Bo Adamson and Wolfgang Feist, the standard is now promoted by the Passivhaus Institut in Darmstadt, Germany. To meet the standard, a home must have an infiltration rate no greater than 0.60 AC/H @ 50 pascals, a maximum annual heating energy use of 15 kWh per square meter (4,755 Btu per square foot), a maximum annual cooling energy use of 15 kWh per square meter (1.39 kWh per square foot), and maximum source energy use for all purposes of 120 kWh per square meter (11.1 kWh per square foot). The standard recommends, but does not require, a maximum design heating load of 10 W per square meter and windows with a maximum U-factor of 0.14. The Passivhaus standard was developed for buildings in central and northern Europe; efforts are underway to clarify the best techniques to achieve the standard for buildings in hot climates. job site in Falmouth, Massachusetts, architect Steve Baczek specified double-stud walls. The frame of a Passivhaus may not be as exciting as the thick layers of insulation, the high-tech mechanical ­systems, or the triple-glazed windows, but it plays a very important supporting role in achieving success.

What Architects Need to Know About Attic Kneewalls

Posted on June 25, 2014 by Allison A. Bailes III, PhD, GBA Advisor in Building Science

We were working on a project, so we got a set of plans to get started. It includes the attic kneewall and vaulted ceiling section you see at right. This is typical of plans that architects draw, and builders build houses this way all the time. Unfortunately, it contains several errors. Can you spot them?

An Energy-Self-Sufficient Community

Posted on June 24, 2014 by Andrew Dey in Guest Blogs

From a distance, Feldheim looks like many other rural villages in Germany: a cluster of buildings surrounded by farmland and forests. The backdrop includes numerous wind turbines, but that’s not unusual in Germany’s breezy north. What is unusual is that there are two signs welcoming visitors to Feldheim: the typical yellow sign that is found at the edge of every village, and another in blue and white announcing that Feldheim is an “Energieautarker Ortsteil,” or an energy self-sufficient district.

The ‘Lock-In’ Concept and Passivhaus Construction

Posted on June 23, 2014 by matthew omalia in Guest Blogs

Alan Gibson (my GO Logic colleague) and I just returned from the 18th annual International Passive HouseA residential building construction standard requiring very low levels of air leakage, very high levels of insulation, and windows with a very low U-factor. Developed in the early 1990s by Bo Adamson and Wolfgang Feist, the standard is now promoted by the Passivhaus Institut in Darmstadt, Germany. To meet the standard, a home must have an infiltration rate no greater than 0.60 AC/H @ 50 pascals, a maximum annual heating energy use of 15 kWh per square meter (4,755 Btu per square foot), a maximum annual cooling energy use of 15 kWh per square meter (1.39 kWh per square foot), and maximum source energy use for all purposes of 120 kWh per square meter (11.1 kWh per square foot). The standard recommends, but does not require, a maximum design heating load of 10 W per square meter and windows with a maximum U-factor of 0.14. The Passivhaus standard was developed for buildings in central and northern Europe; efforts are underway to clarify the best techniques to achieve the standard for buildings in hot climates. Conference in Aachen, Germany. This incredible three-day conference featured some of the superstars in the Passivhaus community as well as influential European policy makers, including Dr. Wolfgang Feist, founder of the Passivhaus Institut.

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