The most recent blogs at Green Building Advisor

A Post-Passivhaus Paradigm for Energy-Efficient Design

Posted on February 17, 2014 by alan abrams in Guest Blogs

Last night, I enjoyed an intense conversation with my friend Bill Updike. Bill, who has been closely following the developing partnership between PHIUS and Building Science Corporation, is the green building specialist at the Washington, D.C. Department of the Environment.

We were talking about cost-effective energy-efficient design, and Bill tossed off a comment that the key to any design — at least in our mixed-humid climate here in Maryland — should be the latent loadCooling load that results when moisture in the air changes from a vapor to a liquid (condensation). Latent load puts additional demand on cooling systems in hot-humid climates. of the building. When he said that, my mind lit up like a pinball machine showing three cherries.

EMFs and Human Health

Posted on February 14, 2014 by Martin Holladay, GBA Advisor in Musings of an Energy Nerd

Every now and then, green builders are approached by clients who are worried about exposure to electromagnetic fields (EMFs). Such clients have read that EMF exposure can make them sick, and they’re interested in building a house that minimizes EMF exposure.

In the modern world, EMFs are ubiquitous. Most of us are surrounded every day by weak electric and magnetic fields that are generated by electrical wires, home appliances, cell phones, and broadcasting equipment.

Our Top-Efficiency Heat-Recovery Ventilator

Posted on February 13, 2014 by Alex Wilson in Energy Solutions

In last week's blog I reviewed some of the general strategies used for ventilating buildings — or not. This week, I’ll zero in on the types of balanced ventilationMechanical ventilation system in which separate, balanced fans exhaust stale indoor air and bring in fresh outdoor air in equal amounts; often includes heat recovery or heat and moisture recovery (see heat-recovery ventilator and energy-recovery ventilator). in which heat is recovered from the outgoing airstream to preheat the incoming fresh air.

Understanding Air Barriers, Vapor Barriers, and Drainage Planes

Posted on February 12, 2014 by Allison A. Bailes III, PhD, GBA Advisor in Building Science

Is housewrap a vapor barrier? What's the purpose of building paperTypically referring to Grade D building paper, this product is an asphalt-impregnated kraft paper that looks a lot like a lightweight asphalt felt. The Grade D designation has come to mean that the building paper passes ASTM D779 (minimum 10-minute rating with the “boat test”) and different products are called out as “30-minute” or even “60-minute” based on D779 results. At times confused with roofing felt, roofing felts and building paper differ in two ways: felts are made of recycled-content paper, building papers of virgin paper; felts are made of a heavier stock paper; building papers a lighter stock. See also roofing felt.? Who'll stop the rain? I've covered this topic in various forms before, but the confusion about what the different building materials do is so widespread that I have to keep coming back to it.

I'm going to keep it simple here so maybe we can get a few more people to use the proper terms, and especially to know when not to use the term “vapor barrier” ... and when not to use it.

A Review of Siga Wigluv Air-Sealing Tape

Posted on February 11, 2014 by Matt Risinger in Guest Blogs

Every house needs four control layers. In order of importance, these layers need to provide:

  1. 1. Water control
  2. 2. Air control
  3. 3. Vapor control
  4. 4. Thermal control

The building codes have dictated the levels of thermal control and vapor control that builders must adhere to, and nearly every builder in the U.S. knows off the top of their head the R-valueMeasure of resistance to heat flow; the higher the R-value, the lower the heat loss. The inverse of U-factor. of the insulation in their walls and attics.

The Big Allure of Cheap PV

Posted on February 10, 2014 by Scott Gibson in Q&A Spotlight

Until now, Patrick McCombe has believed that improvements to the envelope of his home should come before an investment in 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. panels. Now he's weighing a deal that seems too good to pass up.

McCombe lives in Connecticut (he's an associate editor at Fine Homebuilding magazine) and he recently attended an informational meeting sponsored by an organization working to lower the cost of 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.. Panels could be purchased or leased, but the bottom line was that with federal and state incentives, McCombe could buy a 10-kilowatt array for $15,000.

Do Homeowners Need to Understand Home Performance?

Posted on February 7, 2014 by Martin Holladay, GBA Advisor in Musings of an Energy Nerd

My father was a college professor who was respected for his scholarship. Yet Dad doesn’t pay much attention to the physical world. If he were asked to define the stack effectAlso referred to as the chimney effect, this is one of three primary forces that drives air leakage in buildings. When warm air is in a column (such as a building), its buoyancy pulls colder air in low in buildings as the buoyant air exerts pressure to escape out the top. The pressure of stack effect is proportional to the height of the column of air and the temperature difference between the air in the column and ambient air. Stack effect is much stronger in cold climates during the heating season than in hot climates during the cooling season., he’d probably guess that it was a type of exhaustion caused by walking past miles of library bookshelves. According to a family legend, the engine of our family’s Volkswagen van had to be rebuilt in 1963 because my father drove thousands of miles without checking the dipstick or changing the engine oil.

Providing Fresh Air in Our Home

Posted on February 6, 2014 by Alex Wilson in Energy Solutions

One of the features in our new house that I’m most excited about barely raises an eyebrow with some of our visitors: the ventilation system. I believe we have the highest-efficiency heat-recovery ventilator (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. ) on the market — or at least it’s right up there near the top.

I’ll describe this Zehnder HRV and its impressive specifications and features — but not until next week. This week I’ll provide a little background on ventilation.

Green Buildings Aren’t Truly Green Without Location Efficiency

Posted on February 5, 2014 by Allison A. Bailes III, PhD, GBA Advisor in Building Science

I was one of the lucky ones. I spent only two hours in my car when the big snowstorm of 2014 hit Atlanta on Tuesday. We got only about 2 inches of snow in my part of the city, but I made the mistake of going out for lunch at a restaurant right next to Emory University and the CDC compound. It took Jeffrey and me an hour and 45 minutes to drive the 2 miles back to the office. In the first photo below, you can see that the roads themselves were still in good shape at 2 o'clock, at least where we were.

Using Interior Poly As an Air Barrier

Posted on February 4, 2014 by Martin Holladay, GBA Advisor in Musings of an Energy Nerd

Back in the 1980s, Canadian energy experts urged builders to use interior polyethylene as an 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. material. If the poly was installed conscientiously, and all seams were sealed with Tremco acoustical sealant, the approach worked well — at least in cold climates.

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