The most recent blogs at Green Building Advisor

Why Don’t More HVAC Contractors Own Duct Leakage Testers?

Posted on October 22, 2012 by Allison A. Bailes III, PhD in Building Science

HVAC(Heating, ventilation, and air conditioning). Collectively, the mechanical systems that heat, ventilate, and cool a building. contractors own a lot of equipment. Of course, they have pressure gauges to test refrigerant charge in air conditioners and heat pumps, and many more pieces of technical equipment. One piece that few contractors own, however, is a duct leakage tester.

With more and more state energy codes requiring duct leakage tests, doesn't it seem obvious that HVAC contractors need to be like plumbers and test their own work before passing it off?

A New Encyclopedia Article on Ductless Minisplits

Posted on October 19, 2012 by GBA Team in Green Building Blog

With each passing month,'s library of articles and blogs gets deeper. For example, we recently added a new article on Ductless Minisplit Heat Pumps to the GBA Encyclopedia.

Ductless minisplits differ from conventional air-source heat pumps in several ways: first of all, they are extremely efficient, in part because of the use of inverterDevice for converting direct-current (DC) electricity into the alternating-current (AC) form required for most home uses; necessary if home-generated electricity is to be fed into the electric grid through net-metering arrangements.-driven compressors. Secondly, many of these units can operate efficiently at very low outdoor temperatures.

Heating With Wood Safely and Efficiently

Posted on October 18, 2012 by Alex Wilson in Energy Solutions

I’ve been heating primarily with wood since I bought our house 31 years ago, though there were a few years following our installation of an oil boiler when wood consumption dropped considerably.

Wood heat has a mixed record, though. It’s a renewable fuel and, assuming that new trees grow up to replace those cut for firewood, it is carbon-neutral, meaning that it doesn’t have a net contribution to global warming. But burning firewood produces a lot of air pollution; in fact, it’s usually our dirtiest fuel.

Designing Superinsulated Walls

Posted on October 17, 2012 by Roger Normand in Guest Blogs

[Editor's note: Roger and Lynn Normand are building a Passivhaus in Maine. This is the 12th article in a series that will follow their project from planning through construction.]

I’ve always enjoyed watching new homes being built. From the humble beginnings of a simple hole in the ground, a job site gradually changes as a succession of tradesmen arrive daily to craft concrete, lumber, roofing, windows, drywall, copper pipes into basic shelter, before giving way to a parade of cabinets, appliances and other finishing touches.

Seasonal Changes in Electrical Loads

Posted on October 16, 2012 by Marc Rosenbaum in Guest Blogs

We all know that residential heating loadRate at which heat must be added to a space to maintain a desired temperature. See cooling load. is highest in the winter and cooling load is highest in the summer. What's a bit more subtle is how the seasons, and how we respond to them, change the loads on other household energy uses.

Do Europeans Make Better Windows Than We Do?

Posted on October 15, 2012 by Scott Gibson in Q&A Spotlight

It should come as no surprise that Europe, home of the Passivhaus standard, produces some outstanding windows. Some builders of high-efficiency houses in North America turn to European window manufacturers for their glazingWhen referring to windows or doors, the transparent or translucent layer that transmits light. High-performance glazing may include multiple layers of glass or plastic, low-e coatings, and low-conductivity gas fill., even though some U.S. and Canadian producers also offer high-performance products of their own.

Is there a way to compare the performance data on windows from these two sources? That’s what Steve Young, now planning a 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. in Climate Zone 5, would like to know.

Rating Windows for Condensation Resistance

Posted on October 12, 2012 by Martin Holladay in Musings of an Energy Nerd

Condensation forms on a surface when the temperature of the surface is below the dew point of the air. During the winter, when the coldest surface in a room is often the window, it’s fairly common to see water droplets or ice on window glass — especially in a room with elevated indoor humidity.

Condensation is more likely to form when indoor relative humidity is high. That’s why it’s more common to see condensation on a bathroom window than a bedroom window.

Good News, Bad News: A Glut of Solar Panels

Posted on October 11, 2012 by Alex Wilson in Energy Solutions

When China dives into a technology, it does so in a big way. Nowhere is this more the case than in 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.) panel manufacturing, where dramatic growth has not only taken a toll on other manufacturers around the world, but also now threatens its own PV industry through rampant oversupply.

This has significant implications for us here in the U.S. — both good and bad.

How to Insulate and Air-Seal Pull-Down Attic Stairs

Posted on October 10, 2012 by Erik North in Guest Blogs

Pull-down attic stairs are super-sized attic hatches that just beg homeowners to store more stuff in their attic. Besides the air-leakage and insulation problems stemming from having a particularly large hole in your ceiling, pull-down stairs creates a potential storage headache.

For homeowners, a storage problem usually means “not enough space.” For energy auditors, a storage problem means using space that ought to filled with insulation for Timmy’s guitar, his old bike, Legos, his new bike, and the unpacked remains of twelve previous moves.

Looking Through Windows — Part 7

Posted on October 9, 2012 by Roger Normand in Guest Blogs

[Editor's note: Roger and Lynn Normand are building a Passivhaus in Maine. This is the 11th article in a series that will follow their project from planning through construction.]

There’s a popular saying here in Maine — “we’re all set” — to signify that the current situation is perfectly fine.

Window selection had so far been the most time-consuming and vexing aspect of the EdgewaterHaus project. That was all behind us. We had made a final decision on an Optiwin-designed Bieber-manufactured Passivhaus-certified windows.

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