Musings of an Energy Nerd

A Conversation With Wolfgang Feist

Posted on October 27, 2010 by Martin Holladay, GBA Advisor

Dr. Wolfgang Feist, the physicist and founder of the Passivhaus Institut in Darmstadt, Germany, began his U.S. speaking tour with a presentation and panel discussion at the Boston Architectural College on October 23, 2010. Among the other speakers at the event were Katrin Klingenberg, the founder of 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. Institute U.S. in Urbana, Illinois.

Navigating Energy Star’s Thermal Bypass Checklist

Posted on October 22, 2010 by Martin Holladay, GBA Advisor

If you’ve ever built an Energy StarLabeling system sponsored by the Environmental Protection Agency and the US Department of Energy for labeling the most energy-efficient products on the market; applies to a wide range of products, from computers and office equipment to refrigerators and air conditioners. home, then you’re familiar with the Thermal Bypass Checklist. Originally adopted on July 1, 2006, the Checklist identifies areas in homes under construction that must be inspected by a certified rater for a house to qualify for an Energy Star label.

Calculating the Minimum Thickness of Rigid Foam Sheathing

Posted on October 15, 2010 by Martin Holladay, GBA Advisor

UPDATED on August 26, 2014 with new information on flash-and-batt requirements in the 2012 IRCInternational Residential Code. The one- and two-family dwelling model building code copyrighted by the International Code Council. The IRC is meant to be a stand-alone code compatible with the three national building codes—the Building Officials and Code Administrators (BOCA) National code, the Southern Building Code Congress International (SBCCI) code and the International Conference of Building Officials (ICBO) code.

If you plan to install exterior rigid foam on the walls of your house, how thick should the foam be? Although the Web site has addressed this question several times in our Q&A column and various blogs, the question continues to perplex readers. New questions along these lines come our way regularly.

The last time I answered the question was at the end of a long, very technical blog. In this blog, I'll cut to the chase.

The History of Superinsulated Houses in North America

Posted on October 10, 2010 by Martin Holladay, GBA Advisor

Several GBA readers have requested a copy of a presentation on “The History of Superinsulated Houses in North America” that I gave at the 14th Annual Westford Symposium on Building Science (August 3, 2010). I also gave the presentation at the annual meeting of the British Columbia Building Envelope Council in Vancouver (September 22, 2010).

Here it is:
The History of Superinsulated Houses in North America

For more on the topic, check out two blogs with overlapping content:

Solar Versus Superinsulation: A 30-Year-Old Debate

Posted on October 8, 2010 by Martin Holladay, GBA Advisor

The oil price shock of 1973 sparked a burst of interest in “solar houses.” During the 1970s, owner-builders all over the U.S. erected homes with extensive south-facing glazingWhen referring to windows or doors, the transparent or translucent layer that transmits light. High-performance glazing may include multiple layers of glass or plastic, low-e coatings, and low-conductivity gas fill. — sometimes sloped, sometimes vertical. Many of these houses included added thermal massHeavy, high-heat-capacity material that can absorb and store a significant amount of heat; used in passive solar heating to keep the house warm at night. — concrete floors, concrete-block walls, or 55-gallon drums filled with water.

Prevent Ice Dams With Air Sealing and Insulation

Posted on October 1, 2010 by Martin Holladay, GBA Advisor

During snowy winters, many northern homes are plagued by ice dams. If your house suffers from wet ceilings during the winter, you may be ready to call up a contractor. Be careful, though: since most contractors don’t understand the causes of ice dams, they often suggest the wrong solution.

Radiant Barriers: A Solution in Search of a Problem

Posted on September 24, 2010 by Martin Holladay, GBA Advisor

A radiant barrier is a shiny panel or flexible membrane used in construction. Although radiant barriers have no R-valueMeasure of resistance to heat flow; the higher the R-value, the lower the heat loss. The inverse of U-factor. , they can be used as part of a building assembly — for example, an assembly made up of a radiant barrier and an air space — to slow heat transfer.

Are Dew-Point Calculations Really Necessary?

Posted on September 17, 2010 by Martin Holladay, GBA Advisor

Most builders understand that condensation can form when warm, moist air encounters a cold surface. Condensation is bad, and builders want to avoid it. There’s a solution, though: According to building scientists, we can prevent condensation problems in walls by determining a wall’s temperature profile and performing a dew-point calculation. This calculation may require the use of a psychrometric chart.

New Green Building Products — September 2010

Posted on September 10, 2010 by Martin Holladay, GBA Advisor

In this new-product roundup, I'll look at a cover for recessed can lights, a new caulk for polyethylene, and several new water-resistive barriers (WRBs) that promise better performance than Tyvek or Typar.

A fire-resistant hat for recessed can lights
A Delaware manufacturer named Tenmat is selling an airtight hat for recessed can lights. Tenmat light covers are made from mineral wool; according to the manufacturer, they are fire-resistant.

Using Rigid Foam As a Water-Resistive Barrier

Posted on September 3, 2010 by Martin Holladay, GBA Advisor

Do foam-sheathed walls also need housewrap? There’s no simple answer to the question.

It is possible to use foam sheathingMaterial, usually plywood or oriented strand board (OSB), but sometimes wooden boards, installed on the exterior of wall studs, rafters, or roof trusses; siding or roofing installed on the sheathing—sometimes over strapping to create a rainscreen. as a water-resistive barrierSometimes also called the weather-resistive barrier, this layer of any wall assembly is the material interior to the wall cladding that forms a secondary drainage plane for liquid water that makes it past the cladding. This layer can be building paper, housewrap, or even a fluid-applied material. (WRB). However, those who choose this route should know:



  • Some brands of foam have been approved for use as a WRB, while others have not.
  • Even if you choose a code-approved foam, you can run afoul of your local building inspector if you don't follow strict fastening and seam-sealing details.
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