Musings of an Energy Nerd

A Chat With Henry Gifford

Posted on February 1, 2013 by Martin Holladay, GBA Advisor

Most builders and designers involved with green building have heard of Henry Gifford. Energy efficiency experts admire his deep knowledge of heating systems and his straight talk about the unacceptably high number of HVAC(Heating, ventilation, and air conditioning). Collectively, the mechanical systems that heat, ventilate, and cool a building. problems in run-of-the-mill new buildings in the U.S. At the headquarters of the United States Green Building Council (USGBCUnited States Green Building Council (USGBC). Organization devoted to promoting and certifying green buildings. USGBC created the LEED rating systems.), on the other hand, he is something of a pariah — due in part to his 2010 lawsuit that accused the USGBC of making “deceptive marketing claims.”

Do I Need a Vapor Retarder?

Posted on January 18, 2013 by Martin Holladay, GBA Advisor

Every couple of weeks, someone sends me an e-mail with a description of a proposed wall assembly and an urgent question: “Do I need a vapor retarder?” Energy experts have been answering the same question, repeatedly, for at least thirty years. Of course, even though I sometimes sigh when I read this recurring question, it’s still a perfectly good question.

Nostalgia for the Hippie Building Heyday

Posted on January 4, 2013 by Martin Holladay, GBA Advisor

A discredited theory of embryonic development held that “ontogeny recapitulates phylogeny” — in other words, that the the developmental stages of an embryo (its ontogeny) mimic the stages of evolutionary development experienced by the species (its phylogeny). One piece of evidence supporting the theory: in early stages of development, a human embryo has a tail.

The Energy Grinch

Posted on December 21, 2012 by Martin Holladay, GBA Advisor

With apologies to Dr. Seuss

Are HRVs Cost-Effective?

Posted on December 7, 2012 by Martin Holladay, GBA Advisor

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.

All About Wall Rot

Posted on November 23, 2012 by Martin Holladay, GBA Advisor

Contractors who specialize in repairing rotten walls won’t run out of work any time soon. The epidemic of wall-rot problems that began more than 20 years ago shows no signs of abating. In fact, wet-wall specialists are often called to investigate problems in developments where most of the homes have rotting walls — and in some cases, these homes are only six years old.

Passivhaus Practitioners Share Their Success Stories

Posted on November 9, 2012 by Martin Holladay, GBA Advisor

A group of about 130 designers, builders, and Passivhaus fans gathered at U Mass Boston on October 27, 2012 to attend a one-day conference organized by 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. New England.

It's impossible for this report to be comprehensive, unfortunately, and I won't be able to do justice to all of the conference events. My report will focus on three speakers: Adam Cohen, Chris Corson, and Roger Normand.

Fans in the Attic: Do They Help or Do They Hurt?

Posted on October 26, 2012 by Martin Holladay, GBA Advisor

There’s a lot of confusion surrounding attic fans. Here at, we regularly receive e-mails from homeowners with questions about attic fans: What’s the purpose of the fan in my attic? How often should I run it? Do I need a bigger fan?

Before addressing these recurring questions, it’s important to define our terms. First, we need to distinguish between three different types of ventilation fans.

Rating Windows for Condensation Resistance

Posted on October 12, 2012 by Martin Holladay, GBA Advisor

Condensation forms on a surface when the temperature of the surface is below the dew point of the air. During the winter, when the coldest surface in a room is often the window, it’s fairly common to see water droplets or ice on window glass — especially in a room with elevated indoor humidity.

Condensation is more likely to form when indoor relative humidity is high. That’s why it’s more common to see condensation on a bathroom window than a bedroom window.

Air Leakage Degrades the Thermal Performance of Walls

Posted on September 28, 2012 by Martin Holladay, GBA Advisor

For the past five years, researchers at the Building Science Corporation (BSC) in Massachusetts have been testing the thermal performance of a variety of wall assemblies as part of an ambitious project to develop a new metric to replace R-valueMeasure of resistance to heat flow; the higher the R-value, the lower the heat loss. The inverse of U-factor. . (I last reported on the project in my August 2011 article, A Bold Attempt to Slay R-Value.)

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