The most recent blogs at Green Building Advisor

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?

Do Combustion Safety Testing Protocols Need Fixing?

Posted on February 26, 2014 by Allison A. Bailes III, PhD, GBA Advisor in Building Science

Burning fuels inside a house can lead to serious health and safety problems. That's why energy auditors perform a variety of combustion safety tests to find potential hazards and recommend fixes.

A couple of weeks ago at the Dry Climate Forum, I heard Vi Rapp, PhD, from Lawrence Berkeley National Lab (LBNL) make an argument for changing the way we do combustion safety testing. It turns out that one of the tests we do may not be as helpful as many people think it is.

Flash and Batt in the Roof

Posted on February 24, 2014 by Scott Gibson in Q&A Spotlight

"Flash and batt" is an insulation technique that combines the air-sealing superiority of spray foam insulation with the cost benefits of fiberglass batts. An inch or two of polyurethane foam seals the cavity and the batt insulationInsulation, usually of fiberglass or mineral wool and often faced with paper, typically installed between studs in walls and between joists in ceiling cavities. Correct installation is crucial to performance. adds R-valueMeasure of resistance to heat flow; the higher the R-value, the lower the heat loss. The inverse of U-factor. without costing an arm and a leg.

That's roughly the plan Dave Frank is considering for the roof of a house — presumably his own house — in Climate Zone 5. But his plan contains a twist: He wants to spray the underside of the roof deck with foam and install the batts between the joists at ceiling level.

What’s the Definition of an ‘R-20 Wall’?

Posted on February 21, 2014 by Martin Holladay, GBA Advisor in Musings of an Energy Nerd

Builders often talk about the R-valueMeasure of resistance to heat flow; the higher the R-value, the lower the heat loss. The inverse of U-factor. of their walls. But if a builder claims to have an R-20 wall, what does that mean?

Building codes commonly include a table listing the minimum prescriptive R-values for walls and ceilings in different climate zones. For example, Table R402.1.1 in the 2012 International Energy Conservation Code (IECC International Energy Conservation Code.) informs builders that the minimum prescriptive R-value for walls in Climate Zones 3, 4, and 5 is “20 or 13+5.”

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