The most recent blogs at Green Building Advisor

Last week’s column looked at efficient but also very expensive ground-source heat pumps; this week we’ll look at a less expensive option that’s becoming more common even in our climate: air-source heat pumps. Traditionally, air-source heat pumps have been an option mainly for more southern climates, because they have to extract heat from the outside air, and when it’s cold out their performance drops significantly.

Musings on Mazria, Lstiburek and Gifford: Part Four
Underfloor air plenums can be done the right way or the wrong way, like most things.

Seems like I have been spending a lot of time at Southface in Atlanta lately. Founded in 1978, Southface is an old-school, “original greenster” nonprofit that supports sustainability in the built environment through education and research.

In August 2008, FMLS, the leading real-estate listing service in the metro-Atlanta area, began including green certifications in its database. Sellers can now add to their listing EarthCraft House, LEED for Homes, and Energy Star certifications, as well as the HERS index, and features such as solar power, Energy Star appliances, and spray-foam insulation. The new National Green Building Standard was not available at the time these details were added to the listing service, but it likely will be added during their next revision.

Lies, damn lies, and statistics

Practically everyone has seen the Staples advertisements on TV featuring the "easy button." Few people question the idea that things should be easier, but maybe more of us should. "Easy" may appear to be a good thing in the short term, but most things that are easy are actually conspiring to cost us our future in terms of excessive waste, overconsumption of resources, environmental damage from energy generation and vehicle pollution, financial suffering, and declines our health.

Question the value of "easy" in daily life

In 1977, a group of Canadian researchers built a demonstration house in Regina. Called the Saskatchewan Conservation House, the nearly airtight building had triple-glazed windows, R-40 wall insulation, R-60 roof insulation, and one of the world’s first heat-recovery ventilators.

The home’s design and engineering team included Robert Besant, Oliver Drerup, Rob Dumont, David Eyre, and Harold Orr. That same year, Gene Leger, a Massachusetts builder, finished a similar superinsulated house in Pepperell, Mass.

Last week I introduced heat pumps and described how they can deliver more heat than is contained in the electricity they consume—while being able to provide cooling as well as heating. I mentioned two different types of heat pumps: air-source and ground-source. This week I’ll cover ground-source (also known as “geothermal” and “geo-exchange”) heat pumps.

Musings on Mazria, Lstiburek and Gifford: Part Three

I just want to set the record straight on one point: I have not imbibed the USGBC Koolaid. I do like its mission, goals, and products, and the organization has the best start of any rating system out there. As I have stated many times before, I’m a biologist by training and I am way into evolutionary biology. That’s all that needs to happen here.

Door design details
The photo at right is from an entry that's just 15 years old. Fortunately, it was able to be repaired. I haven’t always been so lucky. Let’s just say that replacing subfloor and framing is no fun. A safe assumption is that, for one reason or another, doors always leak. They shouldn’t, but they do. Seals wear out. Wind blows. Jambs rot. Sills crack. Weepholes clog. Following are some ways to mitigate the chance of damage.

How do you know if your housewrap really works?

In the good old days, we weatherlapped 3-ft. courses of building paperTypically referring to Grade D building paper, this product is an asphalt-impregnated kraft paper that looks a lot like a lightweight asphalt felt. The Grade D designation has come to mean that the building paper passes ASTM D779 (minimum 10-minute rating with the “boat test”) and different products are called out as “30-minute” or even “60-minute” based on D779 results. At times confused with roofing felt, roofing felts and building paper differ in two ways: felts are made of recycled-content paper, building papers of virgin paper; felts are made of a heavier stock paper; building papers a lighter stock. See also roofing felt. underneath our wall claddings, and that seemed to work just fine. But then along came all sorts of snazzy “gift wrappings” (a.k.a. housewraps) in handy, 9-ft. rolls. Some claimed to be both air barriers as well as water-resistive barriers; others claimed to be vapor permeable. Along the way, it got pretty confusing about just exactly what the housewrap’s job is in our walls. (For a practical and detailed perspective on housewraps, see “Making Sense of Housewrap”.)

Designers of energy-efficient homes — especially homes aiming for net-zero energyProducing 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. use — must inevitably grapple with the question of simplicity versus complexity.

Residential designers can choose from an array of sophisticated appliances that improve comfort and help homeowners reduce energy use. Examples include heat-recovery ventilators (HRVs), condensing boilers, ground-source heat pumps, solar hot water systems, on-demand water heaters, heat-pump water heaters, 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. modules, and co-generation systems.