Musings of an Energy Nerd

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.

Energy Modeling Isn’t Very Accurate

Posted on March 30, 2012 by Martin Holladay, GBA Advisor

Energy consultants and auditors use energy modeling software for a variety of purposes, including rating the performance of an existing house, calculating the effect of energy retrofit measures, estimating the energy use of a new home, and determining the size of new heating and cooling equipment. According to most experts, the time and expense spent on energy modeling is an excellent investment, because it leads to better decisions than those made by contractors who use rules of thumb.

A Real Chainsaw Retrofit

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

When workers need to insulate the walls and roof of an existing building with exterior rigid foam, it often makes sense to cut off the roof overhangs first. With the eaves and rakes removed, wrapping the building in rigid foam is a snap. The missing roof overhangs can later be rebuilt by scabbing the necessary framing on the outside of the foam.

Solar Thermal is Dead

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

In the northern half of the U.S. — and even much of the South — installing a residential solar hot water system doesn’t make any sense. It’s time to rethink traditional advice about installing a solar hot water system, because it’s now cheaper to heat water with a photovoltaic (PV) array than solar thermal collectors.

In short, unless you’re building a laundromat or college dorm, solar thermal is dead.

A Superinsulated House in Rural Minnesota

Posted on March 16, 2012 by Martin Holladay, GBA Advisor

Electric resistance heating systems have a bad reputation. While the required equipment is cheap (and sometimes cheap-looking), homes with electric heat are known for their high fuel bills.

Occupant Behavior Makes a Difference

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

Energy experts often repeat the cliché, “There’s no such thing as a zero-energy home — just zero-energy homeowners.” Energy monitoring data from two well-publicized Massachusetts homes — the so-called Montague Urban Homestead house in Turners Falls and the home of Matt and Laura Beaton in Shrewsbury — prove the cliché to be true.

The High Cost of Deep-Energy Retrofits

Posted on March 2, 2012 by Martin Holladay, GBA Advisor

How much does it cost to perform a deep-energy retrofit at a 100-year-old single-family home? Thanks to a recent study in Utica, New York, we now know the answer: about $100,000.

The research was sponsored by New York State Energy Research and Development Authority (NYSERDA), an agency that administers programs funded by public benefit charges tacked onto electric utility bills. The program paid for deep-energy retrofits at four wood-framed buildings in Utica, New York.

Carl and Abe Write a Textbook

Posted on February 24, 2012 by Martin Holladay, GBA Advisor

Carl Seville, this website’s resident green building curmudgeon and blogger, has teamed up with Abe Kruger, an energy rater and BPI Building Analyst, to write a new textbook, Green Building: Principles and Practices in Residential Construction.

An Introduction to Photovoltaic Systems

Posted on February 17, 2012 by Martin Holladay, GBA Advisor

By now, photovoltaic(PV) Generation of electricity directly from sunlight. A photovoltaic cell has no moving parts; electrons are energized by sunlight and result in current flow. (PVPhotovoltaics. Generation of electricity directly from sunlight. A photovoltaic (PV) cell has no moving parts; electrons are energized by sunlight and result in current flow.) panels are familiar to most Americans. You’ve seen them on your hand-held calculator, on top of illuminated highway signs, and maybe even on your neighbors’ roofs. With PV systems becoming more common, perhaps you’ve been dreaming of making some homemade electricity. The dream is achievable, as long as you own a sunny patch of lawn or an unshaded south-facing rooftop, and as long as you have a bank balance of several thousand dollars.

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