The most recent blogs at Green Building Advisor

Looking Through Windows — Part 5

Posted on September 26, 2012 by Roger Normand in Guest Blogs

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

Strike up the band: we have – finally – achieved the Passivhaus standard with Unilux windows!

Marc Rosenbaum, our energy consultant, ran the 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. Planning Package (PHPP) energy modeling software and arrived at a heat load of 4.74 KBTU1,000 Btus/sq. ft./year, a mere 0.01 below the 4.75 limit. Talk about a photo-finish squeaker!

Inefficient Hot Water Piping Layouts Waste Hot Water

Posted on September 25, 2012 by Gary Klein in Guest Blogs

What is the key to an efficient piping layout for domestic hot water? The answer is to keep the volume of hot water between the water heater and the tap as small as possible. The difficulty is that most buildings have only one source of hot water and the many uses are spread throughout the floor plan.

Raining, Dripping, Crying Duct Boots

Posted on September 25, 2012 by Allison A. Bailes III, PhD in Building Science

I've seen it over and over: The central air conditioner's ceiling registers raining down onto the floor. The insulation liner on the duct in the crawl space holding a gallon or two of water. The office that has spots appearing on the ceiling. Such problems are not at all uncommon, although they should be.

Vapor Barriers Redux

Posted on September 24, 2012 by Scott Gibson in Q&A Spotlight

Few topics in building science seem to have caused as much confusion as the use of a polyethylene vapor barrier in exterior walls.

Once routinely used by builders to prevent the migration of interior moisture into wall cavities, polyethylene is no longer recommended for houses unless they’re built in extremely cold climates.

What’s Wrong With This Window Installation?

Posted on September 21, 2012 by GBA Team in Green Building Blog

Readers are invited to identify as many installation errors they can spot in the attached photo of a window installed in the rough opening of a new home.

This is the latest in our ongoing series, “What’s Wrong With This Picture?” (To see two previous photos in the series, click the links in the box below.)

The photo comes from James Steacy of IBACOS (a Building America program partner in Pittsburgh, Pennsylvania).

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.

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