Musings of an Energy Nerd

A New Ground-Mounted Solar Array

Posted on October 24, 2014 by Martin Holladay, GBA Advisor

I’ve lived in an off-grid house for the past 39 years. Since I make my own electricity, my electricity costs are much higher than those of most Americans. Because of my off-grid lifestyle, I often lack perspective when I try to help people who ask questions about ordinary energy choices. (I’ve had to compensate for my lack of relevant experience by undertaking anthropological studies of my grid-connected neighbors.)

Dense-Packed Cellulose and a Wrong-Side Vapor Barrier

Posted on October 17, 2014 by Martin Holladay, GBA Advisor

Does the exterior 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. on a double-stud wallConstruction system in which two layers of studs are used to provide a thicker-than-normal wall system so that a lot of insulation can be installed; the two walls are often separated by several inches to reduce thermal bridging through the studs and to provide additional space for insulation. accumulate worrisome quantities of moisture in late winter? Several researchers are now looking into this question, and Green Building Advisor has been sharing the researchers' findings as the information becomes available.

It’s Not About Space Heating

Posted on October 10, 2014 by Martin Holladay, GBA Advisor

If you design a “pretty good house” with R-20 basement walls, R-31 above-grade walls, an R-49 ceiling, triple-glazed windows, a minisplit heat pumpHeating and cooling system in which specialized refrigerant fluid in a sealed system is alternately evaporated and condensed, changing its state from liquid to vapor by altering its pressure; this phase change allows heat to be transferred into or out of the house. See air-source heat pump and ground-source heat pump., and an 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. , what should you do next to reduce your energy bills? Maybe aim for the PassivhausA 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. standard?

Wolfgang Feist Defends Thick Insulation

Posted on October 3, 2014 by Martin Holladay, GBA Advisor

Dr. Wolfgang Feist is the founder of the Passivhaus Institut in Darmstadt, Germany. On September 22, 2014, after Feist gave an address at a Passive House conference in Portland, Maine, he agreed to be interviewed. (For links to my two previous interviews with Dr. Feist, see the “Related Articles” sidebar below.)

Q. What will it take for a higher percentage of new buildings to be built to the Passivhaus standard?

Report from the Passive House Conference in Maine

Posted on September 26, 2014 by Martin Holladay, GBA Advisor

The North American 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. Network held a two-day conference in Portland, Maine, this month. The well-attended conference drew attendees from all over the U.S., as well as from China, the U.K., and Germany.

Brick Buildings Need Roof Overhangs

Posted on September 23, 2014 by Martin Holladay, GBA Advisor

I'm in Portland, Maine, for the North American 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. Network conference. Yesterday morning I walked a few blocks from my hotel to the conference site, through downtown Portland.

The old commercial district here has lots of handsome old three-story and four-story brick buildings. I love to look at the details on these older buildings. At first glance, it may appear that architectural ornament has been randomly applied to these façades; but if one pays attention, it soon becomes clear that most of these façade elements have a function.

New Books on Green Building

Posted on September 19, 2014 by Martin Holladay, GBA Advisor

If you are a cold-climate architect looking for a reference book that provides guidance on designing energy-efficient superinsulated buildings, I strongly suggest that you buy William Maclay’s The New Net ZeroProducing as much energy on an annual basis as one consumes on site, usually with renewable energy sources such as photovoltaics or small-scale wind turbines. Calculating net-zero energy can be difficult, particularly in grid-tied renewable energy systems, because of transmission losses in power lines and other considerations.. It’s the best book on the topic by far.

All About Attics

Posted on September 12, 2014 by Martin Holladay, GBA Advisor

Most six-year-olds can draw a house. The typical child’s depiction of a house shows a rectangular building with a door and a few windows, topped by a gable roof.

This type of house is fairly common in most areas of the U.S. If the house was built 100 or more years ago, it usually had a cellar or basement underneath the first floor and an attic above the top floor.

All About Microwave Ovens

Posted on September 5, 2014 by Martin Holladay, GBA Advisor

A microwave oven uses less energy than a conventional oven. Even though this statement is broadly true, a microwave oven isn’t always the most efficient way to cook.

So what appliance should you use to heat up or cook your dinner: A gas stovetop? An electric-resistance stovetop? An induction stovetop? A gas oven? An electric oven? A countertop toaster oven? A crockpot? Or a microwave oven?

If all you care about is energy efficiency, it’s possible to come up with an answer to this question — but the answer will depend on the quantity and the type of food you are cooking.

Get Ready for Smart Appliances

Posted on August 29, 2014 by Martin Holladay, GBA Advisor

Utility executives and some energy-efficiency experts have been dreaming for years of a smart electricity grid connected to smart appliances that can be remotely controlled. In many North American cities, however, the installation of smart meters has faced strong opposition from some homeowners. The resulting fallout has amounted to a public relations nightmare for electric utilities.

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