The most recent blogs at Green Building Advisor

Get Ready for Heat-Pump Water Heaters

Posted on September 20, 2012 by Alex Wilson in Energy Solutions

Last week I wrote about “hybrid” water heaters, a relatively new type of water heater that includes features of both storage and tankless models. This week I’ll cover another type of water heater that is also (confusingly) referred to as “hybrid”: heat-pump water heaters. These produce over twice as much hot water for each unit of electricity consumed as any other type of electric water heater (storage or tankless).

Video Series: Replacing a Window in a Brick House

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

Brick walls can seriously complicate window installation and can sometimes confuse even the most experienced builders. Fortunately for us, Mike Sloggatt, who has thirty years' experience working on brick houses, was available to show us how to assess the situation and do the job right.

Getting Into Hot Water — Part 2

Posted on September 18, 2012 by Marc Rosenbaum in Guest Blogs

In my last blog, I discussed the basics of our domestic hot water (DHW) load, and looked briefly at adding a solar hot water system to satisfy most of that load. What I decided to do first was to try a 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. (HPWH), partly because it was a much simpler and less costly installation, and partly because I was just curious to see how well one would work.

Looking Through Windows — Part 4

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

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

We have been comparing two window options for EdgewaterHaus: German-manufactured Unilux windows, and Canadian-made windows from Thermotech Fiberglass. I’ll talk about Thermotech in this blog; a previous blog discussed our impressions of the Unilux windows.

Study Shows That Expensive Windows Yield Meager Energy Returns

Posted on September 14, 2012 by Martin Holladay in Musings of an Energy Nerd

An architectural cliché from the 1970s — the passive solar home with large expanses of south-facing glass — is making a comeback. In recent years, we’ve seen North American designers of 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. buildings increase the area of south-facing glass to levels rarely seen since the Carter administration.

What’s the explanation for all this south-facing glass? We’re told that there’s no other way for designers to meet the energy limit for space heating required by the Passivhaus standard: namely, a maximum of 15 kWh per square meter per year.

Hybrid Water Heaters

Posted on September 13, 2012 by Alex Wilson in Energy Solutions

In last week’s blog I compared tankless and storage water heaters and explained why tankless water heaters often don’t make that much sense.

Getting into Hot Water — Part 1

Posted on September 12, 2012 by Marc Rosenbaum in Guest Blogs

Dick and Tim Mavro, with the help of a large friend of Tim's named Justin, came and took our oil heating system away. I was glad to see the truck drive off with all that equipment on the trailer. Now I have to find a home for the Vermont Castings gas heater, and then we'll be fossil-fuel-free, at least as far as site energy is concerned.

Tips from a Commercial Demolition Company

Posted on September 11, 2012 by J.D. Elder in Guest Blogs

The demolition of a building is a carefully orchestrated, thoroughly researched affair. Demolition contractors must be conscientious about both employee safety and environmental safety, or else risk losing their business licenses. Just like general contractors, demolition experts are required to follow OSHA standards for employee safety. And demolition firms must also abide by EPA standards guiding environmentally safe deconstruction techniques. Hazardous construction materials, such as asbestosMineral fiber once commonly used in many building materials, including insulation, fireproof siding, and resilient flooring. Inhalation of invisible asbestos fibers can lead to chest and abdominal cancers as well as scarring of the lungs. The use of asbestos in some products has been banned by the EPA and the U.S. Consumer Products Safety Commission; manufacturers also have adopted voluntary limitations on its use. When found in older buildings (most commonly in floor tiles, pipe and furnace insulation, or asbestos shingles), the product's friability is a major determinant in how it must be handled during renovations. More information:, must be safely removed before a building can be demolished.

Photovoltaics, Part 2: Enter the Dollar

Posted on September 10, 2012 by Christopher Briley in Green Architects' Lounge

Not too long ago, our own Jesse Thompson (known for his "What's Bothering Jesse?" segment on the Green Architects' Lounge) wrote a great article, PV Systems Have Gotten Dirt Cheap. It was a wakeup call for many.

The Difference Between Storage and Tankless Water Heaters

Posted on September 6, 2012 by Alex Wilson in Energy Solutions

There are two primary types of water heaters: storage and tankless. In this column I’ll try to explain the differences between these two approaches and offer some guidance on choosing between them. (There are also “hybrid” water heaters with features of both that I’ll cover in a future blog.)

Storage water heaters

Most water heaters are storage models. These are insulated tanks holding 20 to 120 gallons with either electric heating elements or gas burners. The storage tank stratifies with hot water at the top and cold incoming water at the bottom, so that as you draw off hot water (from the top), you get consistently hot water until the hot water is nearly depleted. The “first-hour rating” tells you how many gallons of hot water can be delivered in an hour. 

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