Musings of an Energy Nerd

Belgian Passivhaus is Rendered Uninhabitable by Bad Indoor Air

Posted on June 1, 2012 by Martin Holladay, GBA Advisor

The first single-family Passivhaus in the U.S. was completed by Katrin Klingenberg in 2004. Klingenberg’s superinsulated home in Urbana, Illinois includes two unusual features: a ventilation system that pulls fresh outdoor air through a buried earth tubeVentilation air intake tube, usually measuring 8 or more inches in diameter and buried 5 or more feet below grade. Earth tubes take advantage of relatively constant subterranean temperatures to pre-heat air in winter and pre-cool it in summer. In humid climates, some earth tubes develop significant amounts of condensation during the summer, potentially contributing to indoor air quality problems., and walls that include an interior layer of OSB. These details were not invented by Klingenberg; she adopted practices that were commonly used by European Passivhaus builders.

Window-Mounted Air Conditioners Save Energy

Posted on May 25, 2012 by Martin Holladay, GBA Advisor

Window-mounted air conditioners (also called room air conditioners) aren’t particularly efficient; the best available models have an EEREnergy-efficiency rating or energy-efficiency ratio. As most commonly used, EER is the operating efficiency of a room air conditioner, measured in Btus of cooling output divided by the power consumption in watt-hours; the higher the EER, the greater the efficiency. of about 10 or 11. Central air conditioners (also called whole-house air conditioners or split-system air conditioners) are significantly more efficient; it’s possible to buy one with an EER of 14 or even 15.

So if you care about energy efficiency, you should use a central air conditioner, not a window air conditioner — right? Well, not necessarily.

Choosing an Energy-Efficient Refrigerator

Posted on May 18, 2012 by Martin Holladay, GBA Advisor

Because federal appliance efficiency standards have gotten more stringent, new refrigerators use much less energy than those sold in the 1970s. These days, it’s fairly easy to find a full-size refrigerator that requires only 350 to 500 kWh per year — significantly less than the 1,000 kWh/year energy hogs of yore.

When Do I Need to Perform a Load Calculation?

Posted on May 11, 2012 by Martin Holladay, GBA Advisor

In my last three blogs, I discussed the basics of heat-loss and cooling load calculations. The unfortunate truth about these calculations is that fast methods aren’t particularly accurate, and accurate methods require making measurements, checking specifications, and entering data into a computer program — in other words, a significant investment of time.

So how should builders go about making these calculations?

Calculating Cooling Loads

Posted on May 4, 2012 by Martin Holladay, GBA Advisor

A few decades ago, residential air conditioning was very rare in colder areas of the U.S., and cooling load calculations were usually unnecessary. These days, however, new U.S. homes routinely include air conditioning equipment, even in Minnesota, so most U.S. builders are faced with the need to calculate cooling loads.

Report from the NAHB Green Conference

Posted on May 1, 2012 by Martin Holladay, GBA Advisor

The NAHBNational Association of Home Builders, which awards a Model Green Home Certification. Green conference is being held this week (April 29 to May 1, 2012) in Nashville, Tennessee. Several employees and bloggers — including Dan Morrison, Michael Chandler, Peter Yost, Ted Clifton, and me — are attending.

Nashville has a number of famous buildings, including a full-scale replica of the Parthenon. Nashville's Parthenon isn't made of quarried marble, however; it's made of concrete. So how's the concrete quality? Do the columns resemble marble?

How to Perform a Heat-Loss Calculation — Part 2

Posted on April 27, 2012 by Martin Holladay, GBA Advisor

To continue last week’s discussion of heat-loss calculation methods, let’s consider a simple rectangular building, 20 feet by 30 feet, with 8-foot ceilings. Let’s assume it has an 8-foot-high basement with uninsulated concrete walls; the below-grade portion of the basement is 7 feet high, with 1 foot above grade.

To keep things simple, we’ll assume that the house has a flat roof, and that each side of the house has two windows (each 3 ft. by 4 ft.) and one door (3 ft. by 7 ft.). The house doesn’t have a chimney.

How to Perform a Heat-Loss Calculation — Part 1

Posted on April 20, 2012 by Martin Holladay, GBA Advisor

I’m going to devote the next several blogs to a discussion of heat-loss and heat-gain calculations. These calculations are the first step in the design of a home’s heating and cooling system.

In order to address this big topic in little bites, I’ll start by discussing heat-loss calculations. I’ll get around to heat-gain calculations and cooling equipment in a future blog.

Heat-Pump Water Heaters Come of Age

Posted on April 13, 2012 by Martin Holladay, GBA Advisor

The least expensive way to heat domestic hot water is with natural gas. Homes without access to natural gas usually choose an electric water heater, since electricity is generally cheaper than propane.

Are Tankless Water Heaters a Waste of Money?

Posted on April 6, 2012 by Martin Holladay, GBA Advisor

Although tankless water heaters are, on average, more efficient than traditional tank-style water heaters, they’re also more expensive — so expensive, in fact, that many potential customers wonder whether their high cost can ever be justified by likely energy savings.

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