Musings of an Energy Nerd

Zen and the Art of Grading

Posted on June 7, 2013 by Martin Holladay, GBA Advisor

Green builders have an uneasy relationship with chainsaws and bulldozers. To some environmentalists, these noisy inventions conjure up images of ecosystem destruction and irresponsible land development.

However, just like a hammer or a level, a bulldozer is just a tool. It can be used for good or ill.

Bulldozers are extremely handy when you need to change the grade of a site. Grading matters, and novice builders who ignore grading will eventually be forced to pay attention to the topic.

Is Your Pool an Energy Hog?

Posted on May 31, 2013 by Martin Holladay, GBA Advisor

If your home has a swimming pool, your pool pump may use more electricity than any other appliance in your home — as much as three times the electricity used by your refrigerator. Many residential pools in the U.S. have 1.5-horsepower or 2-horsepower pumps that draw 2,000 watts or more. If you’re not paying attention, you may be running your pool pump for 24 hours a day — even though your pool might be perfectly clean with only 6 hours of pump operation per day.

Climate-Specific Air Conditioners

Posted on May 24, 2013 by Martin Holladay, GBA Advisor

If you live in a humid climate (for example, in Florida), you need an air conditioner that does a good job of dehumidification. But if you live in a dry climate (for example, in Nevada), dehumidification is almost irrelevant, because the outdoor air is so dry. In Nevada, all you need is an air conditioner that lowers the temperature of the air in an energy-efficient way.

Energy Upgrades for Beginners

Posted on May 17, 2013 by Martin Holladay, GBA Advisor

Owners of older homes often contact GBAGreenBuildingAdvisor.com and ask, “What can I do to make my home more energy-efficient?” My standard answer goes something like this: “The first step is to hire a certified rater to perform an energy auditEnergy audit that also includes inspections and tests to assess moisture flow, combustion safety, thermal comfort, indoor air quality, and durability. of your home. The audit report will include a tailor-made list of retrofit measures to address your home’s specific problems.”

Passivhaus Buildings Don’t Heat Themselves

Posted on May 10, 2013 by Martin Holladay, GBA Advisor

For years, the English-language website of the Passivhaus Institut in Germany provided this definition: “A 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. is a building in which a comfortable interior climate can be maintained without active heating and cooling systems. The house heats and cools itself, hence ‘passive.’”

All About Thermal Mass

Posted on May 3, 2013 by Martin Holladay, GBA Advisor

UPDATED on December 4, 2013 with a citation of recent research findings.

What’s the deal with thermal mass? Since manufacturers of materials that incorporate concrete often exaggerate the benefits of thermal mass, it’s easy to get cynical and conclude that the buzz around thermal mass is all hype. But in many climates, it’s actually useful to have a lot of thermal mass inside your house. Just keep in mind that thermal mass may not be as beneficial as its boosters pretend.

Choosing HVAC Equipment for an Energy-Efficient Home

Posted on April 26, 2013 by Martin Holladay, GBA Advisor

Why are the smallest available American furnaces rated at about 40,000 Btuh? Back in the 1960s, a house in a cold climate may have needed such a powerful furnace — or even one rated at 60,000 or 80,000 Btuh. But these days, many new homes have design heating loads that are much smaller — as low as 10,000 to 20,000 Btuh. Over the past 30 years, building envelopes have become tighter and better insulated, but U.S. furnace manufacturers haven’t kept up with the times. For mysterious reasons, they don’t offer furnaces that are small enough for today’s energy-conscious builders.

Green Building for Beginners

Posted on April 19, 2013 by Martin Holladay, GBA Advisor

Green building websites can be confusing. One site might tell you that a green home should include spray foam insulation, a tankless water heater, and a geothermal heating system. After you’ve absorbed this advice, you visit another website, where you learn that spray foam is a dangerous petrochemical, tankless water heaters are overpriced gadgets, and “geothermal” systems aren’t really geothermal.

Insulating Low-Slope Residential Roofs

Posted on April 12, 2013 by Martin Holladay, GBA Advisor

UPDATED on September 12, 2014

There are lots of ways to insulate a low-slope roof, and most of them are wrong. In older buildings, the usual method is to install fiberglass batts or cellulose on top of the leaky ceiling, with a gap of a few inches (or sometimes a few feet) between the top of the insulation and the roof sheathingMaterial, usually plywood or oriented strand board (OSB), but sometimes wooden boards, installed on the exterior of wall studs, rafters, or roof trusses; siding or roofing installed on the sheathing—sometimes over strapping to create a rainscreen. . In some cases, but not all, there is an attempt to vent the air space above the insulation to the exterior.

Are Affordable Ground-Source Heat Pumps On the Horizon?

Posted on April 5, 2013 by Martin Holladay, GBA Advisor

My grandfather, William L. Holladay, was a refrigeration and cooling engineer. Decades ago, he wrote a pioneering, speculative article on ground-source heat pumps, “The Heat Pump: What it does, and what it may do someday.” The article appeared in the October 1948 issue of Engineering and Science Monthly. (For a basic explanation of how a heat pump works, and the difference between an air-source heat pumpHeat pump that relies on outside air as the heat source and heat sink; not as effective in cold climates as ground-source heat pumps. and a ground-source heat pump, see Heat Pumps.)

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