The most recent blogs at Green Building Advisor

Where is This Water Coming From?

Posted on April 13, 2015 by Scott Gibson in Q&A Spotlight

Writing from Climate Zone 6, GBAGreenBuildingAdvisor.com reader David Metzger is looking for some advice about his standing-seam metal roof. More to the point, why is there water dripping from the soffit when the winter's accumulation of snow and ice starts to melt?

Making Fiberglass Work

Posted on April 13, 2015 by Lee Kurtas in Green Building Blog

When building science and home efficiency really took off in the mid-1990s, insulation contractors started hearing regularly about how the type of insulation used affects a building’s energy efficiency. Blower-door testing and thermal imaging of existing homes proved that fiberglass—as it’s typically installed—didn’t perform as well as other types of insulation, especially spray foam. As a result, builders and architects doing projects with energy-performance benchmarks started specifying spray foam as a way to ensure better airtightness and thermal resistance.

Using a Glycol Ground Loop to Condition Ventilation Air

Posted on April 10, 2015 by Martin Holladay, GBA Advisor in Musings of an Energy Nerd

Most energy-efficient homes include a mechanical ventilation system — often an HRV(HRV). Balanced ventilation system in which most of the heat from outgoing exhaust air is transferred to incoming fresh air via an air-to-air heat exchanger; a similar device, an energy-recovery ventilator, also transfers water vapor. HRVs recover 50% to 80% of the heat in exhausted air. In hot climates, the function is reversed so that the cooler inside air reduces the temperature of the incoming hot air. or ERV(ERV). The part of a balanced ventilation system that captures water vapor and heat from one airstream to condition another. In cold climates, water vapor captured from the outgoing airstream by ERVs can humidify incoming air. In hot-humid climates, ERVs can help maintain (but not reduce) the interior relative humidity as outside air is conditioned by the ERV. that brings in fresh outdoor air while simultaneously exhausting an equal volume of stale indoor air. The main problem with introducing outdoor air into a house is that the air is at the wrong temperature — too cold during the winter and too hot (and often too humid) during the summer.

In Defense of Inconvenient Truths about Vinyl Siding

Posted on April 9, 2015 by Fernando Pages Ruiz in Guest Blogs

A recent blog of mine, “The Counterintuitive Cladding,” discussed the “green” bona fides 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. The blog struck a variety of nerves, including from those who mistook an obvious opinion piece for a poorly written scientific paper.

Diagnostic Tools for Energy-Minded Remodelers

Posted on April 9, 2015 by Don Jackson in Green Building Blog

The past several years have seen a flurry of activity on the home-energy front. Federal tax incentives and dozens of rebate programs have focused attention on cutting residential energy consumption. Energy audits are now common in many areas of the country, and building codes have stepped up insulation and air-sealing requirements, and are even beginning to require blower-door testing and duct-testing on new construction. Homeowners are more aware than ever of these trends, with more and more wishing to tighten their houses so that they can save money on their utility bills.

Should the DOE Increase Furnace Efficiency Standards?

Posted on April 8, 2015 by Allison A. Bailes III, PhD, GBA Advisor in Building Science

Do you know when the U.S. last raised furnace efficiency standards? It was 1987. Do you know how long the U.S. Department of Energy (DOEUnited States Department of Energy.) has been trying to change that? At least since 2007.

The past eight years have been a sad case of industry heavyweights preventing progress on this important issue. The DOE, however, just proposed a new rule, so we might finally see some action here. Do you know when it's set to go into effect, if passed?

Best Practices for Zero Net Energy Buildings

Posted on April 7, 2015 by Marc Rosenbaum in Guest Blogs

This is a synopsis of a peer-reviewed article by Marc Rosenbaum, found in the Fall 2014 edition of BuildingEnergy magazine, and a preview of what's in store for students of Marc's BuildingEnergy Masters Series Course, Zero Net Energy Homes.

A Better Approach to Design/Build

Posted on April 6, 2015 by Ann Edminster, GBA Advisor in Green Building Blog

The most ambitious project I’ve ever worked on is a spectacular, über-green home in the foothills west of Silicon Valley. The owners, Linda Yates and Paul Holland, contacted me in May 2006 to request that I brief their project team on LEED for HomesLeadership in Energy and Environmental Design. LEED for Homes is the residential green building program from the United States Green Building Council (USGBC). While this program is primarily designed for and applicable to new home projects, major gut rehabs can qualify. , then in its prepilot stage. Six years later, in November 2012, I had the pleasure of leading a tour of the house as part of the U.S. Green Building Council’s Greenbuild conference. I invited Fine Homebuilding editor Brian Pontolilo to tag along.

The 10 Most Important Water Stories in 2014

Posted on April 6, 2015 by Peter Gleick and J. Carl Ganter in Guest Blogs

1. The California drought becomes an emergency
California’s multi-year drought grew dire enough in 2014 to prompt Governor Jerry Brown to declare a drought emergency in January. By the end of the year, California had experienced the driest and hottest 36 months in its 119-year instrumental record. Some researchers described the drought as 1) the worst in over 1200 years and 2) evidence of rising temperatures globally as climate changes accelerate. As of mid-January, the drought is continuing.

How to Install Rigid Foam On Top of Roof Sheathing

Posted on April 3, 2015 by Martin Holladay, GBA Advisor in Musings of an Energy Nerd

A roof over a vented, unconditioned attic does not need to include any insulation. However, most cathedral ceilings and low-slope (flat) roofs are insulated roof assemblies: with this kind of roof, the insulation follows the slope of the roof.

Insulated roof assemblies can be vented or unvented. There are lots of different ways to insulate this type of roof, but one of the best methods calls for the installation of rigid foam insulation above the roof 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. .

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