Musings of an Energy Nerd

Vapor Retarders and Vapor Barriers

Posted on March 12, 2010 by Martin Holladay, GBA Advisor

Although building science has evolved rapidly over the last 40 years, one theme has remained constant: builders are still confused about vapor barriers.

Any energy expert who fields questions from builders will tell you that, year after year, the same questions keep coming up: Does this wall need a vapor barrier? Will foam 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. trap moisture in my wall? How do I convince my local building inspector that my walls don’t need interior poly?

The Energy-Efficiency Pyramid

Posted on March 5, 2010 by Martin Holladay, GBA Advisor

UPDATED on September 24, 2013

We’re all familiar with the food pyramid — the triangle with grains and cereals at the bottom and fats and sugars at the top. Inspired by the food pyramid, a Midwestern electric utility, Minnesota Power, has created a useful graphic called the energy conservation pyramid. (According to a Minnesota Power spokesperson, the originator of the conservation pyramid was Bob McLean, the chief operating officer at Hunt Utilities Group.)

Air Conditioner Basics

Posted on February 26, 2010 by Martin Holladay, GBA Advisor

What does a Vermonter know about air conditioning? I live so close to the Canadian border that half of the radio stations are in French. If my house needs cooling, I just let the fire in the wood stove die down.

When I first began reporting on air conditioning topics over a decade ago, I felt out of my element. Impelled by the certainty that there’s no such thing as a dumb question, I’ve managed over the years to badger a few air-conditioner experts, all of whom contributed to my education. So now I finally know the difference between an evaporator coil and a condenser coil.

Duct Leakage Testing

Posted on February 19, 2010 by Martin Holladay, GBA Advisor

For years, Americans who would never put up with leaky plumbing pipes have been willing to accept leaky ducts. While water damage is hard to ignore, the damage caused by leaky ducts is more subtle. Yet leaky ducts not only waste huge amounts of energy — they can also lead to comfort complaints, moisture problems, mold, and rot.

Energy-Efficient Garage Doors

Posted on February 12, 2010 by Martin Holladay, GBA Advisor

If you’re shopping for a garage door, the door’s energy performance may not matter — especially if you don’t heat your garage. However, there are a few reasons why you might be looking for a well-insulated, draft-free garage door:

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  • A good overhead door on an attached garage can keep the garage — and therefore the house — a little warmer than a leaky door.
  • Since cars can be hard to start in sub-zero weather, homeowners in very cold climates — even those with unheated garages — may want a garage door that limits heat loss.
  • It’s OK to Skimp On Insulation, Icynene Says

    Posted on February 5, 2010 by Martin Holladay, GBA Advisor

    While energy experts often advise builders to exceed minimum code requirements for insulation, Icynene Incorporated, a manufacturer of open-cell spray polyurethane foam, is swimming against the tide. Surprisingly, Icynene is trying to convince builders to install less insulation than the code requires.

    Blower Door Basics

    Posted on January 29, 2010 by Martin Holladay, GBA Advisor

    Leaky homes are hard to heat and hard to cool. The only way to know whether your home is leaky or tight is to measure its air leakage rate with a blower door. A blower door is a tool that depressurizes a house; this depressurizationSituation that occurs within a house when the indoor air pressure is lower than that outdoors. Exhaust fans, including bath and kitchen fans, or a clothes dryer can cause depressurization, and it may in turn cause back drafting as well as increased levels of radon within the home. exaggerates the home’s air leaks, making the leaks easier to measure and locate.

    An energy-efficient house must be as airtight as possible. Many older U.S. homes are so leaky that a third to a half of the home’s heat loss comes from air leaks.

    HRV or ERV?

    Posted on January 22, 2010 by Martin Holladay, GBA Advisor

    After investigating various ventilation options, many residential designers conclude that they want either a heat-recovery ventilator (HRV(HRV). Balanced ventilation system in which most of the heat from outgoing exhaust air is transferred to incoming fresh air via an air-to-air heat exchanger; a similar device, an energy-recovery ventilator, also transfers water vapor. HRVs recover 50% to 80% of the heat in exhausted air. In hot climates, the function is reversed so that the cooler inside air reduces the temperature of the incoming hot air. ) or an energy-recovery ventilator (ERV(ERV). The part of a balanced ventilation system that captures water vapor and heat from one airstream to condition another. In cold climates, water vapor captured from the outgoing airstream by ERVs can humidify incoming air. In hot-humid climates, ERVs can help maintain (but not reduce) the interior relative humidity as outside air is conditioned by the ERV.). They often remain confused, however, about which of the two devices to choose.

    Every tight home needs a mechanical ventilation system.

    Home Dashboards Help to Reduce Energy Use

    Posted on January 15, 2010 by Martin Holladay, GBA Advisor

    In recent years, the technology of our cars has advanced at a more rapid rate than the technology of our homes. A new car’s dashboard has gauges that display all kinds of information, including the amount of fuel in the car’s tank, the oil pressure, the electrical system voltage, and sometimes the tire pressure. Many new cars even have a real-time fuel-efficiency gauge that displays miles per gallon.

    The Uncertain Future of Phoenix and Las Vegas

    Posted on January 8, 2010 by Martin Holladay, GBA Advisor

    The American Southwest is running out of water. For a powerful reminder, if any is needed, of why builders in Western states should integrate water-conservation strategies in all new buildings, check out a new book by James Lawrence Powell, Dead Pool: Lake Powell, Global Warming and the Future of Water.

    Powell’s message is stark: according to scientists’ best predictions, millions of Americans living in the Southwest will face unprecedented water shortages in the next few decades.

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