The most recent blogs at Green Building Advisor

New Englanders Love Heat Pumps

Posted on March 12, 2014 by Allison A. Bailes III, PhD, GBA Advisor in Building Science

Last week I went to NESEA's Building Energy conference, and I think I heard three terms more than any others: 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., 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., and 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.. (The second most popular trio was beer, wine, and whisky, but that may have something to do with the folks I was hanging out with.)

So let's get right to the important question here: Why do these people in the cold climate of New England love heat pumps so much?

Settling In to My Renovated Cottage

Posted on March 11, 2014 by Carl Seville, GBA Advisor in Green Building Curmudgeon

I’ve been living in my renovated house for about two months now, and, with the exception of my hot water issue and ice on my windows, everything is working pretty well.

HVAC for a ‘Pretty Good House’

Posted on March 10, 2014 by Scott Gibson in Q&A Spotlight

Matt Mesa is looking ahead to retirement in a new, one-level house in Hood River, Oregon. It's going to be a Pretty Good House, a phrase coined to describe a well-insulated house of an appropriate size.

All About Washing Machines

Posted on March 7, 2014 by Martin Holladay, GBA Advisor in Musings of an Energy Nerd

About 82% of U.S. homes have a clothes washer. Each of these appliances is used, on average, to wash about 300 loads of laundry per year. On an annual basis, residential clothes washers use more energy than dishwashers but less than refrigerators.

Heat-Pump Water Heaters in Cold Climates

Posted on March 6, 2014 by Alex Wilson in Energy Solutions

In last week's blog I wrote about the GE GeoSpring heat-pump water heaterAn appliance that uses an air-source heat pump to heat domestic hot water. Most heat-pump water heaters include an insulated tank equipped with an electric resistance element to provide backup heat whenever hot water demand exceeds the capacity of the heat pump. Since heat-pump water heaters extract heat from the air, they lower the temperature and humidity of the room in which they are installed. in our new house — first, why we decided to go with electric water heating over solar thermal (since we use solar to generate as much electricity as we will consume), and then how we decided on a heat-pump water heater instead of one of the other electric water heating options. This week, I’ll get into a little more about heat-pump water heaters and some of the issues that come into play when installing them in cold climates.

How to Make Your Dumb Heat Pump Defrost Intelligent

Posted on March 5, 2014 by Allison A. Bailes III, PhD, GBA Advisor in Building Science

Heat pumps can get frosty when they run in heating mode. It doesn't happen all that often, but it's a fact of life when you're trying to extract heat from cold, outdoor air.

Why I Hate, Hate, Hate Skylights

Posted on March 4, 2014 by Erik North in Guest Blogs

Why do I hate skylights? Because I’ve rarely seen one that isn’t either causing a problem or in the process of causing one. They fall squarely into a category with recessed lights and cathedral ceilings: Homeowners love them and energy pros come to loathe them.

They lead to uncomfortable conversations that can be summarized as: Yes, they’re a problem; no, they can’t be easily fixed.

Strength in Numbers

Posted on March 3, 2014 by Paul Eldrenkamp in Guest Blogs

I’ve had three extended learning experiences in my career that have taught me the power of numbers. Thanks to my friends John Abrams of South Mountain Company and Jamie Wolf of Wolfworks, along with key support from the Northeast Sustainable Energy Association and the Yestermorrow Design Build School, I’m about to embark on a fourth such experience — one which promises to be the most exciting and powerful of all.

Exhaust-Only Ventilation Systems and Radon

Posted on February 28, 2014 by Martin Holladay, GBA Advisor in Musings of an Energy Nerd

Articles on mechanical ventilation commonly warn builders that exhaust-only ventilationMechanical ventilation system in which one or more fans are used to exhaust air from a house and make-up air is supplied passively. Exhaust-only ventilation creates slight depressurization of the home; its impact on vented gas appliances should be considered. systems can pull radonColorless, odorless, short-lived radioactive gas that can seep into homes and result in lung cancer risk. Radon and its decay products emit cancer-causing alpha, beta, and gamma particles. into a house through foundation cracks. The warning makes intuitive sense: after all, an exhaust-only ventilation system works by depressurizing a house with respect to the outdoors, and it seems obvious that 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. could pull soil gases into a basement.

One thing I’ve learned over the years, however, is that just because an idea is intuitively obvious, doesn’t mean it’s true. Throughout history, many observers have speculated; far fewer have actually made measurements.

Deciding on a Water Heater

Posted on February 27, 2014 by Alex Wilson in Energy Solutions

As we build more energy-efficient houses, particularly when we go to extremes with insulation and air tightness, as with 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. projects, water heating becomes a larger and larger share of overall energy consumption. In fact, with some of these ultra-efficient homes, annual energy use for water heating now exceeds that for space heating — even in cold climates.

So, it makes increasing sense to focus a lot of attention on water heating. What are the options, and what makes the most sense when we’re trying to create a highly energy-efficient house?

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