The Hallowell Acadia heat pump can operate at temperatures below 0 degrees and still perform significantly better than electric-resistance heat.

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.

All this week, webcasting service BrightTALK is honoring Earth Day by providing five days of free green building presentations. Many of the presenters are world-class.

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The ClimateMaster ground-source heat pump is recognized by the GreenSpec directory as a green product.

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.

The myth that plants will clean the air is a seductive one: if true, we could fix indoor air quality problems without expensive changes to mechanical systems and without worrying about what materials we introduce to the indoor environment. There is scientific evidence that plants clean the air, pulling formaldehyde and other pollutants out of the air and turning CO2 to oxygen (after all, this is what trees and outdoor plants do for the earth).

(For those who might feel that the Climate Denial Crock of the Week post needs some balance.)

Peter Sinclair is a graphic artist, illustrator, animator, and environmental awareness advocate. He's been posting a series of "Climate Denial Crock of the Week" videos on the internet.

An air-source heat pump is like a window air conditioner: Running one way, it cools, running the other, it heats. When outside air is cold enough, electric resistance heaters kick in. Most air source heat pumps work better in moderate climates than cold ones, although there are specialized models for cold areas.

I used to think that electric heating should be avoided at all cost. After all, most of our electricity is produced from highly polluting and greenhouse-gas- spewing coal power plants or from nuclear power plants with their own, quite different, risks.

EBN reported last October on a California law requiring annual energy-use reporting for all nonresidential buildings. (Commercial owners will have to disclose energy use starting in 2010.) How far behind is a national law? Last week, a 648-page draft was released of the American Clean Energy and Security Act of 2009 (ACES) bill by House Representatives Henry A. Waxman (D-CA), chairman of the Energy and Commerce Committee, and Edward J.

On March 27, a shake-table simulation of twice the ground acceleration of the '94 Northridge CA earthquake was run in the Network for Earthquake Engineering Simulation's Large Structures Laboratory at the University of Nevada on a full-scale model of a strawbale housing unit developed in the wake of the devastating 2005 Kashmir 7.6 magnitude quake that killed nearly 100,000 people and left over three million homeless in Pakistan.