Musings of an Energy Nerd

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.

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.

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.

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.

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.

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.

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.

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.

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.”

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