The most recent blogs at Green Building Advisor

Getting Into Hot Water — Part 3

Posted on October 1, 2012 by Marc Rosenbaum in Guest Blogs

In a previous blog, I described our decision to get rid of our oil-fired boiler. When our oil boiler went away, the hot water tank did also, and this gave me an opportunity to relocate the new water heater directly below the two bathrooms. This reduces the wait time to get hot water to the tap substantially, and the tank is now only half the distance from the kitchen as well.

Air Leakage Degrades the Thermal Performance of Walls

Posted on September 28, 2012 by Martin Holladay in Musings of an Energy Nerd

For the past five years, researchers at the Building Science Corporation (BSC) in Massachusetts have been testing the thermal performance of a variety of wall assemblies as part of an ambitious project to develop a new metric to replace R-valueMeasure of resistance to heat flow; the higher the R-value, the lower the heat loss. The inverse of U-factor. . (I last reported on the project in my August 2011 article, A Bold Attempt to Slay R-Value.)

(At Least) 3 Things Are Wrong With This Window Installation

Posted on September 28, 2012 by GBA Team in Green Building Blog

Last week, published a photo of a recently installed window in an new house under the headline, “What's Wrong With This Picture?”

The photo showed the window from the interior. Some of the flexible flashing material was visible on the rough sill and the rough jamb.

The list of problems outlined below was prepared by James Steacy of IBACOS.

Updated Encyclopedia Page on Photovoltaic Systems

Posted on September 27, 2012 by GBA Team in Green Building Blog

Only a few years ago, the installed cost of a grid-connected 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. (PVPhotovoltaics. Generation of electricity directly from sunlight. A photovoltaic (PV) cell has no moving parts; electrons are energized by sunlight and result in current flow.) system was about $7 per watt. Now that inexpensive PV modules are widely available, the price has been cut in half (to about $3.50 per watt) in many areas of the U.S.

As architect Jesse Thompson pointed out in his guest blog, PV Systems Have Gotten Dirt Cheap, falling PV prices are a game-changer.

Drainline Heat Exchangers

Posted on September 27, 2012 by Alex Wilson in Energy Solutions

Over the past few weeks I’ve written about various strategies to produce hot water efficiently. We’ve seen that tankless water heaters are more efficient than storage water heaters (though are not without their drawbacks), and we’ve learned that heat-pump water heaters produce two to three times as much heat per unit of electricity consumed as electric water heaters that rely on electric resistance heat.

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).

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