Musings of an Energy Nerd

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:

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  • 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.
  • Window Reflections Can Melt Vinyl Siding

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

    UPDATED September 3, 2013

    In almost every corner of the U.S., reports are increasing of vinylCommon term for polyvinyl chloride (PVC). In chemistry, vinyl refers to a carbon-and-hydrogen group (H2C=CH–) that attaches to another functional group, such as chlorine (vinyl chloride) or acetate (vinyl acetate). siding that has been melted by sunlight bouncing off nearby windows. This melted-siding pandemic makes vinyl manufacturers very nervous — so nervous that the topic is rarely discussed.

    ‘Walls Need to Breathe’ and 9 Other Green Building Myths

    Posted on August 20, 2010 by Martin Holladay, GBA Advisor

    Just for fun, I’ve rounded up ten oft-repeated statements that are either half-truths or outright falsehoods. I’m sure some readers will disagree with my conclusions; if you’re one of them, don’t hesitate to post a comment.

    Saving Energy With Manual J and Manual D

    Posted on August 13, 2010 by Martin Holladay, GBA Advisor

    If you’ve been paying attention to energy-efficiency experts and green-building Web sites, you probably know that it’s important to properly size your HVAC(Heating, ventilation, and air conditioning). Collectively, the mechanical systems that heat, ventilate, and cool a building. equipment. Most sources repeat the same advice: oversized furnaces and air conditioners cost too much, waste energy, and sometimes provide lower levels of comfort.

    Sealing Ducts: What’s Better, Tape or Mastic?

    Posted on August 6, 2010 by Martin Holladay, GBA Advisor

    Most residential duct systems have numerous leaks that waste energy and lead to room-to-room pressure imbalances. Unfortunately, though, few building inspectors outside of California bother to enforce existing code requirements that residential duct seams be sealed with mastic or high-quality duct tape.

    Air-Sealing Tapes and Gaskets

    Posted on July 30, 2010 by Martin Holladay, GBA Advisor

    UPDATED March 8, 2013

    After this article was published, Martin Holladay conducted a test of eleven air-sealing tapes on a variety of materials. To read the results of Holladay's testing, see Backyard Tape Test and Return to the Backyard Tape Test.

    Green Building Vocabulary Disputes

    Posted on July 23, 2010 by Martin Holladay, GBA Advisor

    As any builder knows, construction terms vary from job site to job site; one carpenter’s furring strip is another carpenter’s strapping. Like carpenters, building scientists are inconsistent when it comes to technical terms — in part because building science is a relatively young field.

    In new fields of learning (including building science), vocabulary generally wanders at first, and eventually converges once consensus is reached. Reaching agreement on technical terms is useful. It helps achieve a desirable goal: efficient communication.

    One Air Barrier or Two?

    Posted on July 16, 2010 by Martin Holladay, GBA Advisor

    Although building scientists have understood the advantages of airtight construction details for years, few residential plans include air barrierBuilding assembly components that work as a system to restrict air flow through the building envelope. Air barriers may or may not act as a vapor barrier. The air barrier can be on the exterior, the interior of the assembly, or both. details. That’s nuts.

    Do the blueprints show where the air barrier goes?

    Ideally, construction documents should show the location of a building’s air barrier, and should explain how the builder is expected to maintain air-barrier continuity at penetrations and important intersections.

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