The most recent blogs at Green Building Advisor

What’s a Blower Door Good For?

Posted on December 12, 2012 by Allison A. Bailes III, PhD in Building Science

In last week's blog, I suggested that talking about infiltration rates in terms of air changes per hour isn’t an accurate way to portray air leakage. The problem is that you’re dividing by volume but the leaks happen at the surface. I don’t think ACHACH stands for Air Changes per Hour. This is a metric of house air tightness. ACH is often expressed as ACH50, which is the air changes per hour when the house is depressurized to -50 pascals during a blower door test. The term ACHn or NACH refers to "natural" air changes per hour, meaning the rate of air leakage without blower door pressurization or depressurization. While many in the building science community detest this term and its use (because there is no such thing as "normal" or "natural" air leakage; that changes all the time with weather and other conditions), ACHn or NACH is used by many in the residential HVAC industry for their system sizing calculations.50 is going away anytime soon, and I use it myself because everyone else does, even though it’s biased toward larger houses.

A Tough Energy Code Is the Worker’s Friend

Posted on December 11, 2012 by Marc Rosenbaum in Guest Blogs

The Town of West Tisbury passed the Stretch Code at Town Meeting this year. It's a more stringent building code and in essence it speeds up the adoption of the next iteration of the International Energy Code.

Passivhaus versus Net-Zero Energy Buildings

Posted on December 10, 2012 by mike eliason in Guest Blogs

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. (or nearly zero energy building) vs. net zeroProducing as much energy on an annual basis as one consumes on site, usually with renewable energy sources such as photovoltaics or small-scale wind turbines. Calculating net-zero energy can be difficult, particularly in grid-tied renewable energy systems, because of transmission losses in power lines and other considerations. debate has become an ongoing discussion that rears its nerdy head every few months. It really first took grasp shortly before Martin Holladay published his Net Zero versus Passivhaus blog. Recently, the topic has made its way into several conversations – and my arguments for nearly-zero-energy buildings (NZEBs) or NZEBs + renewables always spark a lively conversation.

Are HRVs Cost-Effective?

Posted on December 7, 2012 by Martin Holladay in Musings of an Energy Nerd

From 1977 (when the Saskatchewan Conservation house was built) until 2004 (when the first U.S. Passivhaus was built), North American builders completed hundreds of superinsulated homes. In those days, anyone interested in rating the performance of these homes was probably interested in just one metric: annual energy use.

Using Open-Web Trusses as Rafters for Superinsulated Roofs

Posted on December 6, 2012 by Alex Wilson in Energy Solutions

Last week I wrote about an innovative foundation insulation material, Foamglas, that we used in our new house in Dummerston. This week I’ll talk about the open-web rafters we’re using to achieve a superinsulated roof.

First, a little background. There are several approaches to creating highly insulated roofs.

Air Leaks Happen at the Surface, Not in the Volume

Posted on December 5, 2012 by Allison A. Bailes III, PhD in Building Science

During the Westford Symposium on Building Science in 2010,* I was watching the tweets from the people who were there. At one point, I saw this one: “@EFL_Guy: ‘Air leaks through surfaces, not volume’ Joe Lstiburek.” I'd been meaning to blog about this issue for a while, so I wrote an article about it. Now, a couple of years later, it's time for a little update.

Insulating Stud Cavities in Existing Homes

Posted on December 4, 2012 by Erik North in Guest Blogs

I was about to launch into an article on insulating empty wall cavities in an older house when I realized that the topic is best broken down into two sections: a survey of the products you can use to insulate your wall cavities, and a discussion of installation techniques and methods. I'm just glad I realized that in the first paragraph as opposed to the fifth page. So this article will focus on insulation materials.

Seeing Red on a Green Property Appraisal — Part 3

Posted on December 3, 2012 by Roger Normand in Guest Blogs

[Editor's note: Roger and Lynn Normand are building a Passivhaus in Maine. This is the 17th article in a series that will follow their project from planning through construction.]

Getting an appraisal to value green enhancements requires the appraiser to take two actions: (1) To recognize and list the green enhancements on the appraisal form; and (2) To assign a value to these enhancements.

Another GreenBuild Down

Posted on November 30, 2012 by Carl Seville in Green Building Curmudgeon

After missing GreenBuild 2011 in Toronto, I was excited to be back this year in San Francisco, a city I visit so frequently that I consider it my second home. GreenBuild is a big conference, with attendence in the range of 30,000, down slightly from a few years ago, but still very impressive. It was held in the Moscone Center, well located in downtown San Francisco.

On the Jobsite with Foamglas

Posted on November 29, 2012 by Alex Wilson in Energy Solutions

In my role with Environmental Building News and our GreenSpec Product Database, I get plenty of opportunities to research and write about innovative building products. That’s one of the really fun aspects of my job.

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