Musings of an Energy Nerd

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.

Energy and Construction Photos from Greece

Posted on July 9, 2010 by Martin Holladay, GBA Advisor

You can put away your building science notebooks; this blog is simply a collection of photos from my recent vacation in Greece.

While the purpose of my trip was relaxation, I still managed to point my camera at a few construction sites and examples of renewable-energy equipment.

When Sunshine Drives Moisture Into Walls

Posted on July 2, 2010 by Martin Holladay, GBA Advisor

Builders have worried about wintertime vapor diffusionMovement of water vapor through a material; water vapor can diffuse through even solid materials if the permeability is high enough. ever since 1938, when Tyler Stewart Rogers published an influential article on condensation in the Architectural Record. Rogers’ article, “Preventing Condensation in Insulated Structures,” included this advice: “A vapor barrier undoubtedly should be employed on the warm side of any insulation as the first step in minimizing condensation.”

Five Energy Nerd Classics

Posted on June 25, 2010 by Daniel Morrison

Martin will be back soon. Honest.

Until next Friday, please enjoy some classic Energy Nerd columns from the early days of Green Building Advisor.

Energy Use Is the Most Important Aspect of Green Building
Here, Martin sticks a stake in the ground and takes a stand on what really matters in Green Building.

Slums of the Future
Do the McMansion developments of the housing boom represent tomorrow's slums?

Simplicity Versus Complexity
How to design a heating system: Keep it simple.

Understanding R-Value

The Energy Nerd's Greatest Hits

Posted on June 18, 2010 by Daniel Morrison

Martin is enjoying what may be one of his last opportunities for a family vacation; his oldest son is winding down his high school career, and will leave for college in about a year. All of us at Green Building Advisor support his strong family values and hope he has a great time vacationing on the island of Crete for the next couple of weeks.

Using Ceiling Fans To Keep Cool Without AC

Posted on June 11, 2010 by Martin Holladay, GBA Advisor

When I was a young backpacker traveling through India, Sri Lanka, and Thailand in the 1970s, I couldn’t afford air-conditioned hotels or restaurants. In these tropical conditions, I became quite accustomed to the benefits of Casablanca-style fans.

Although a fan can’t lower the temperature of the air, it can make people feel cooler. Moving air accelerates the rate at which perspiration evaporates from your skin. The evaporation process requires heat, so increased evaporation means that more heat is leaving your body.

Should Green Homes Burn Wood?

Posted on June 4, 2010 by Martin Holladay, GBA Advisor

Environmentalists often argue over the wisdom of heating homes with wood. Strong arguments can be marshaled on both sides of this debate, so I’ll do my best to represent both positions before summing up.

Housewrap in a Can: Liquid-Applied WRBs

Posted on May 28, 2010 by Martin Holladay, GBA Advisor

When it’s time to cover 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. with 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), most residential builders choose plastic housewrap, asphalt felt, 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., or rigid foam sheathing. Some commercial builders, however, choose a fifth option: a liquid-applied building wrap.

Liquid-applied WRBs come in a bucket and are applied to wall sheathing or concrete blocks with a roller or a spray rig. These products cure to form a tenacious, flexible coating that seals small cracks and penetrations.

Testing a Thirty-Year-Old Photovoltaic Module

Posted on May 21, 2010 by Martin Holladay, GBA Advisor

In 1980, after living in the woods of Vermont without electricity for five years, I bought my first 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. (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.) module. Responding to a small ad in Mother Earth News, I sent a check to Joel Davidson, a back-to-the-land urban refugee who was facilitating a bulk purchase of PV panels. From his off-grid acreage in Pettigrew, Arkansas, Davidson was selling 33-watt Arco Solar modules for $275 each.

Many people ask, “How long do solar panels last?” To mark the 30th anniversary of my first PV module, I decided to climb up on my roof and bring it down for testing.

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