Musings of an Energy Nerd

All About Water-Resistive Barriers

Posted on January 21, 2011 by Martin Holladay, GBA Advisor

UPDATED on September 18, 2013

By now, almost all builders know the importance of installing 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) behind siding. Most types of siding leak, so it’s a good idea (and a code requirement) to install a WRB to protect your wall 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. from any wind-driven rain that gets past the siding.

A WRB can be vapor-permeable, like Tyvek, or vapor-impermeable, like foil-faced polyisocyanurate. As long as the wall assembly is designed to dry out when it gets wet, either vapor-permeable or vapor-impermeable WRBs work well.

Questions and Answers About Air Barriers

Posted on January 14, 2011 by Martin Holladay, GBA Advisor

UPDATED on December 12, 2014

Builders of a certain age — say, those older than about 55 or 60 — started their careers at a time when no one talked about air leakage or air barriers. Back in the early 1970s, even engineers were ignorant about air leakage in buildings, because the basic research hadn’t been done yet.

Times have changed, and most residential building codes now require builders to include details designed to reduce air leakage. Today’s young carpenters are working on job sites where air barriers matter.

Net-Zero-Energy versus Passivhaus

Posted on January 7, 2011 by Martin Holladay, GBA Advisor

In Europe, builders interested in energy efficiency are gravitating to the 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. Meanwhile, American researchers — and a few American builders — have developed a fascination with the idea of the net-zero-energy house. The U.S. Department of Energy has established as a goal that new buildings in the U.S. will be built to a net-zero-energy standard by 2030.

Creating a Conditioned Attic

Posted on December 31, 2010 by Martin Holladay, GBA Advisor

UPDATED April 22, 2014

Millions of Americans live in states where residential HVAC(Heating, ventilation, and air conditioning). Collectively, the mechanical systems that heat, ventilate, and cool a building. contractors routinely install ductwork in unconditioned attics. In many cases, these attics also contain a variety of appliances, including air handlers, furnaces, or water heaters.

The Pros and Cons of Advanced Framing

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

Advanced framingHouse-framing techniques in which lumber use is optimized, saving material and improving the energy performance of the building envelope., also called optimum value engineering (OVE), is a framing system that aims to pare the amount of lumber used to frame buildings to the bare minimum. Advanced framing was developed in the 1960s by the Department of Housing and Urban Development as a way for builders to reduce costs.

In recent years, the decades-old framing system has been adopted by many green builders. These new advanced framing devotees are focused less on the cost-cutting aspects of the framing system than on its other virtues, including energy and materials savings.

Christmas Carols from the Energy Nerd

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

UPDATED December 23, 2010:
Click on the mp3 link above to listen to a recorded version of "The Blower Door Man Is Coming to Town." Many thanks to Greg Cutler and Peter Troast of The Energy Circle for recording one of this year's carols.

Rudolph the Sloppy Builder

You know all about Norm Abram
And that old builder named Bob
But do you recall
The most infamous builder of all?

Foam Under Footings

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

A wide variety of residential foundation types, including monolithic slabs, crawl space foundations, and basement foundations, can lose heat due to poorly detailed insulation at the concrete footings. That’s because many construction details, including some details on the Web site, fail to address thermal bridgingHeat flow that occurs across more conductive components in an otherwise well-insulated material, resulting in disproportionately significant heat loss. For example, steel studs in an insulated wall dramatically reduce the overall energy performance of the wall, because of thermal bridging through the steel. through foundation footings.

All About Glazing Options

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

Everybody has an opinion on windows, and there’s a lot to talk about. Which frame material do you prefer: wood or fiberglass? Do you like double-hungs, sliders, or casements? Who provides better warranty service, Marvin or Pella?

Window selection is a complicated topic, so I'll approach the issue in small bites. In this article I’ll focus on 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..

Fastening Furring Strips to a Foam-Sheathed Wall

Posted on November 26, 2010 by Martin Holladay, GBA Advisor

UPDATED March 1, 2012

If you’re building a house with 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. , and your siding is installed over vertical rainscreenConstruction detail appropriate for all but the driest climates to prevent moisture entry and to extend the life of siding and sheathing materials; most commonly produced by installing thin strapping to hold the siding away from the sheathing by a quarter-inch to three-quarters of an inch. strapping installed on top of the foam, how should you attach the strapping? Most builders screw the strapping through the foam into the studs; so far, so good. But what length screws should you use? And how closely should you space the screws?

Makeup Air for Range Hoods

Posted on November 19, 2010 by Martin Holladay, GBA Advisor

Most homes have several exhaust appliances. These typically include a bathroom fan (40-200 cfm), a clothes dryer (100-225 cfm), and perhaps a power-vented water heater (50 cfm), a wood stove (30-50 cfm), or a central vacuum cleaning system (100-200 cfm). But the most powerful exhaust appliance in most homes is the kitchen range-hood fan (100-1,200 cfm).

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