The most recent blogs at Green Building Advisor

Passivhaus Crosses the Atlantic

Posted on October 23, 2009 by Martin Holladay, GBA Advisor in Musings of an Energy Nerd

Last weekend I attended the Fourth Annual North American Passive House Conference in Champaign-Urbana, Ill. The conference offered a great opportunity to learn more about the Passivhaus standard and to discuss low-energy buildings with an experienced group of architects, engineers, and builders.

Improving Water Heater Efficiency

Posted on October 21, 2009 by Alex Wilson in Energy Solutions

Last week I wrote about a high-tech solution for water heating--heat-pump water heaters that can cut costs by more than half compared to conventional electric water heating. This week, I’ll address the low-tech efficiency side of water heating.

How Deep Is Your Footprint?

Posted on October 19, 2009 by Ann Edminster, GBA Advisor in Green Building Blog

In my house we’ve been talking a lot lately about consumption—more specifically, about the relationship between consumption and our carbon footprint. In the green-building world, when we talk about a footprint, it’s usually related to building design.

Return-Air Problems

Posted on October 16, 2009 by Martin Holladay, GBA Advisor in Musings of an Energy Nerd

In homes with a single central return-air grille, return air often struggles to find its way back to the furnace. The result: room-to-room pressure imbalances that lead to uneven room temperatures, comfort complaints, higher energy costs, and even moisture problems in walls and ceilings.

When a furnace comes on, heated air is pushed through supply ducts to registers in each heated room in a house. If the forced-air system is properly designed, the house includes return-air ducts to convey air back to the furnace to be heated again, in a kind of continuous loop.

Pro/Con: Does Passivhaus Make Sense Over Here?

Posted on October 14, 2009 by Martin Holladay, GBA Advisor in Green Building Blog

John Straube, a prominent building science professor and a principal of the Building Science Corporation in Westford, Mass., asserts that applying the German 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. standard to North American houses often results in expensive details that yield few energy-saving benefits.

In response, two prominent energy consultants, Marc Rosenbaum of Energysmiths and David White of Right Environments, challenge some of Straube's conclusions and defend the goals and methods of the Passivhaus standard.

Comparing Passivhaus Homes to Other Low-Energy Homes

Posted on October 14, 2009 by John Straube in Green Building Blog

[Editor's note: This article originally appeared on the Building Science Web site as "The Passive House (Passivhaus) Standard—A comparison to other cold climate low-energy houses." is presenting Straube's article as one of a pair of Pro/Con articles. The response from Marc Rosenbaum and David White is titled "In Defense of the Passive House Standard."]

In Defense of the Passive House Standard

Posted on October 14, 2009 by Marc Rosenbaum in Green Building Blog

By Marc Rosenbaum and David White

We recently read John Straube's paper, "Comparing Passivhaus Standard Homes to Other Low-Energy Homes," comparing the Passive House (PH) standard with the Building Science Corporation (BSC) cold-climate approach.

My 2nd Commandment: Don’t Give Anything Away!

Posted on October 13, 2009 by Michael Strong, LEED Associate, CGP in Business Advisor

In my last blog, I proposed that when building green we follow a variation of the 2,400-year-old Hippocratic Oath, Primum non nocere (“Above all else, do no harm”), as our 1st Commandment. I reinterpreted that oath from a business perspective as “Above all else, do not leave any money on the table building green.” Like a good doctor, I believe that before we can make things better, we have to agree not to make things worse. And if we are going to start out losing money when building green, we will definitely be making things worse.

Heat-Pump Water Heaters

Posted on October 13, 2009 by Alex Wilson in Energy Solutions

There’s a revolution underway with electric water heating. It could be just as significant as the shift from top-loaders to horizontal-axis front-loaders that we’ve seen in the laundry appliance industry.

For years, electric water heaters were simply insulated tanks with a couple of electric-resistance elements that heated the water. These have worked pretty well, and with the highest-insulation products, the “Energy Factor” (a standardized measure of efficiency that factors in losses through the insulated tank) of the best products get pretty close to 1.0 (100% efficient).

Water, Water Everywhere

Posted on October 11, 2009 by Carl Seville, GBA Advisor in Green Building Curmudgeon

Having little knowledge and less experience in rainwater collection, it was a lucky break for me that the American Rainwater Catchment Systems Association or ARCSA national conference was held in my hometown recently. It was so close, in fact, that I was able to ride my bike to the event. I heard several good presentations from pioneers in rainwater collection with very interesting theories that really made me think. Issues that were raised included the value of rainwater vs.

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