The most recent blogs at Green Building Advisor

How Duct Leakage Steals Twice

Posted on July 23, 2014 by Allison A. Bailes III, PhD, GBA Advisor in Building Science

Duct leakage is a big deal. It's one of the top three energy wasters in most homes (air leakage and cable TV set-top boxes being the other two). Researchers at Lawrence Berkeley National Lab found that duct systems leak on average about 10% of the supply air they move and 12% of the return air. (Download pdf and also see Dana Dorsett's comment below, #1.) In far more homes than you might suspect, the main culprit is a disconnected duct, as shown in the photo at right, but a typical duct system has a lot of other leaks, too.

Are LEED-Certified Buildings Energy-Efficient?

Posted on July 22, 2014 by Jim Newman in Guest Blogs

There has been some heated discussion lately about how much energy LEEDLeadership in Energy and Environmental Design. LEED for Homes is the residential green building program from the United States Green Building Council (USGBC). While this program is primarily designed for and applicable to new home projects, major gut rehabs can qualify. -certified buildings use. When the U.S. Green Building Council (USGBCUnited States Green Building Council (USGBC). Organization devoted to promoting and certifying green buildings. USGBC created the LEED rating systems.) first came out with its Version 1 LEED Guideline in 2000, a building could earn LEED certification without any points in the energy section.

In the early 2000s, making a building more energy-efficient than the building codes was more of a challenge for architects and engineers than it is today. When applying for LEED certification, they would attempt the “easier” and often less expensive points available under other credits.

An Old House Gets a New Thermomass Basement

Posted on July 21, 2014 by Brian Butler in Guest Blogs

To prepare our bid for a comprehensive renovation project in Cambridge, Massachusetts, we visited the old house several times. On one of the walk-throughs, we realized that the foundation was failing in many places. We therefore proposed to raise the house and replace the entire foundation.

Raising this house was a challenging process, given the tight space and the existing condition of the house.

The 2012 Code Encourages Risky Wall Strategies

Posted on July 18, 2014 by Martin Holladay, GBA Advisor in Musings of an Energy Nerd

Builders who follow the prescriptive requirements of the 2012 International Residential Code (IRCInternational Residential Code. The one- and two-family dwelling model building code copyrighted by the International Code Council. The IRC is meant to be a stand-alone code compatible with the three national building codes—the Building Officials and Code Administrators (BOCA) National code, the Southern Building Code Congress International (SBCCI) code and the International Conference of Building Officials (ICBO) code.) in Climate Zone 6, 7, or 8 are required to install a minimum of “20+5 or 13+10” wall insulation. What does this mean? According to an explanatory footnote in the code, the “First value is cavity insulation, [and the] second is continuous insulation or insulated siding, so ‘13+5’ means R-13 cavity insulation plus R-5 continuous insulation or insulated siding.”

GBA Welcomes New Readers

Posted on July 17, 2014 by GBA Team in Green Building Blog

Now that the Green Building Advisor website is more than five years old, it has over 36,000 web pages. That's a lot of pages. It's no surprise that it can take a while to find what you are looking for in GBAGreenBuildingAdvisor.com's massive archives.

If you are a relative newcomer to GBA, welcome! Here are a few pointers to help you find your way around GBA.

Energy Efficiency Requires More Than an App on Your Smartphone

Posted on July 16, 2014 by Allison A. Bailes III, PhD, GBA Advisor in Building Science

When it comes to air conditioning, there are a lot of bad products and bad ideas out there. Here are a few: You can buy a cover for your condenser that could kill your compressor.

Foundations — Part 2

Posted on July 15, 2014 by Christopher Briley in Green Architects' Lounge

Phil and I have returned to continue our discussion on foundations. In Part One, we covered slabs and frost walls, and in this part we cover basements and crawl spaces.

The Highlights:

Do you really need a basement? If there's no programmatic need for a basement (like the need for a workshop), then perhaps you can do without one.

Insulation: Inside or outside? There are many reasons to insulate on either side. We weigh the pros and cons.

When the Problem Is Heat

Posted on July 14, 2014 by Scott Gibson in Q&A Spotlight

If you have problems dealing with the heat, you probably wouldn't like the desert Southwest, especially when conventional air conditioning is simply too expensive to use on a regular basis.

That seems to be the case for a GBAGreenBuildingAdvisor.com reader who's trying to learn more about building in a climate where the challenge of staying cool far outweighs the minor and occasional inconvenience of staying warm.

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.

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