The most recent blogs at Green Building Advisor

Every House Needs Roof Overhangs

Posted on July 11, 2014 by Martin Holladay, GBA Advisor in Musings of an Energy Nerd

Many residential designers pay too little attention to roof overhangs. Roof overhangs have several important functions: they can protect exterior doors, windows, and siding from rain; they can shade windows when solar heat gainIncrease in the amount of heat in a space, including heat transferred from outside (in the form of solar radiation) and heat generated within by people, lights, mechanical systems, and other sources. See heat loss. is undesirable; and they can help keep basements and crawl spaces dry. A house with improper overhangs can overheat in the summer, can suffer from water entry problems at windows and doors, and can have premature siding rot.

The most common design error is to make roof overhangs too stingy. It’s also possible (although much rarer) for roof overhangs to be too wide.

South-Facing Skylights: Threat or Menace?

Posted on July 10, 2014 by Martin Holladay, GBA Advisor in Musings of an Energy Nerd

There are two kinds of sunrooms: those that have sloped glazingWhen referring to windows or doors, the transparent or translucent layer that transmits light. High-performance glazing may include multiple layers of glass or plastic, low-e coatings, and low-conductivity gas fill. and those that have only vertical glazing. Sunrooms with sloped (or in some cases, curved) glazing are more common (and, of course, more uncomfortable). In order to make sure that these rooms are sunny, they are often located on the south side of the house.

Four Ways to Find the Size of Your Air Conditioner

Posted on July 9, 2014 by Allison A. Bailes III, PhD, GBA Advisor in Building Science

Do you know what size your air conditioner is? In the world of building science, you'll hear a lot of talk about why oversized air conditioners are a bad idea. Why? Briefly, they don't dehumidify as well, short-cycling wears them out quicker, and your home will probably be less comfortable if the air conditioner is too big. But to know if your AC is oversized, first you have to know what size it is.

Foundations — Part 1

Posted on July 7, 2014 by Christopher Briley in Green Architects' Lounge

Not too long ago I found myself in a deep conversation (pun intended) about frost-protected slabs with some other architects and building professionals. I was surprised at the energy surrounding the topic. We all seemed to have developed substantial differences in the details on our own and we were all learning from each other.

I was equally surprised at how fresh this concept seemed — I mean, haven’t we been founding our wood structures on the ground for centuries now? Millennia, even?

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.

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