Report from the NAHB Green Conference

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Report from the NAHB Green Conference

Checking out the concrete quality at local landmarks and learning about green building in Nashville, Tennessee

Posted on May 1 2012 by Martin Holladay, GBA Advisor

The NAHBNational Association of Home Builders, which awards a Model Green Home Certification. Green conference is being held this week (April 29 to May 1, 2012) in Nashville, Tennessee. Several GBAGreenBuildingAdvisor.com employees and bloggers — including Dan Morrison, Michael Chandler, Peter Yost, Ted Clifton, and me — are attending.

Nashville has a number of famous buildings, including a full-scale replica of the Parthenon. Nashville's Parthenon isn't made of quarried marble, however; it's made of concrete. So how's the concrete quality? Do the columns resemble marble?

Like 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 (which looks like freshly painted clapboard, but only from a distance), the concrete columns of Nashville's Parthenon are less convincing up close than they are from 200 yards away. The columns have a kind of exposed-aggregate, sandy finish rather than a smooth-as-marble finish.

The Renaissance Hotel is also made of concrete

Whenever I place concrete, I aim for quality — even if I'm just filling a few Sonotubes. I want to get out the air bubbles and create a smooth finish — and I make sure the rebar is properly placed.


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Why is it that modern buildings with concrete façades so often have terrible concrete quality? I'm thinking, for example, of Paul Rudolph's Art & Architecture building at Yale, a brutalist disaster with concrete so sloppy that the rusting rebar and reinforcing mesh are exposed to the elements.

The NAHB Green conference is being held at the Nashville Convention Center, and many attendees are staying at the attached 25-story hotel, the Renaissance Nashville. The skyscraper is only 20 years old, but its concrete façade is already streaked with rust from projecting steel tie rods or mesh. (See the photo below.) It's hard to say whether these unsightly concrete disasters are due to an architect's ignorance or builder sloppiness. In any case, the concrete buildings of Nashville are no match for those on the Acropolis of Athens.

Signs of a continuing recession

This year's NAHB Green conference is a subdued affair. Attendance is down, and the trade-show floor is downright sleepy.

Residential construction is now at historic lows. Few builders feel flush enough to send many employees to a national conference, so it's no surprise that the conference rooms at the Nashville Convention Center are half-empty this week. Perhaps next year will be better.

In spite of the low attendance numbers, the quality of the presentations here is high. Peter Yost gave a presentation on adhesives and sealants; Dan Morrison gave a presentation on why builders and architects should see the submission of articles to Fine Homebuilding and Green Building Advisor as a marketing opportunity; and Michael Chandler gave a presentation on best practices. Later today, Gord Cooke will give a presentation on air sealing, and Steve Easley will give a presentation on common energy mistakes made by builders.

Peter Pfeiffer blasts eco-bling

Yesterday morning I attended a presentation, "Seeing Beyond the Glare of Eco-Bling," by Peter Pfeiffer, a well-known green architect from Austin, Texas. His presentation included an excellent collection of design tips for people building in hot climates.

Here's a sample of Peter Pfeiffer's wisdom:

“Green building boils down to this: you are aiming for reduced consumption of stuff. Reduced consumption of energy, water, and nonrenewable building materials. Next, you are aiming for improved health and better indoor air quality. Finally, you are aiming for reduced environmental impact. So don’t develop a site outside of town before you consider remodeling a house in town.”

“Don’t underestimate the value of discussing the obvious. If your new windows leak air because you didn’t do any air sealing — because you didn’t use any low-expansion foam — then you won’t get the energy benefit you expect. I know of one owner who spent $30,000 to replace all his single-pane windows with new double-pane low-e windows, and because of air leaks, there was no change in his energy bills.”

“The city of Austin launched its Green Building Program in 1991. We were giving out free 55-gallon rain-barrels. Then someone decided to check whether homes with rain-barrels had any reduction in water use, and it turned out they didn’t, because the barrels didn’t hold enough water to be meaningful. It was just a feel-good program. So that was discontinued.”

“If you do Manual J modeling, then there is something you can get whenever you model one of your houses — and that is intuition. You’ll notice that a living room that faces west needs about half of the cooling tonnage of the house. So intuition tells you that for your next house, you had better cut back on unshaded windows facing west. In a lot of houses, the AC load is being dominated by sunlight coming in through west windows. So, from looking at the Manual J report, you might realize that maybe you don’t have to worry so much about wall insulation, but maybe you should worry more about unshaded west windows.”

“Shade your windows. The overhangs on my house save us more energy than the solar panels on the roof. They also enhance the living quality, because we don’t have to close our blinds; we don’t get glare. Overhangs add comfort and durability to the home.”

“Shading your windows is often more effective at reducing energy use than replacing your windows with new low-e windows.”

“If a home has a swimming pool, the pool pump is often the single largest consumer of energy in the house. Changing a HERSIndex or scoring system for energy efficiency established by the Residential Energy Services Network (RESNET) that compares a given home to a Home Energy Rating System (HERS) Reference Home based on the 2006 International Energy Conservation Code. A home matching the reference home has a HERS Index of 100. The lower a home’s HERS Index, the more energy efficient it is. A typical existing home has a HERS Index of 130; a net zero energy home has a HERS Index of 0. Older versions of the HERS index were based on a scale that was largely just the opposite in structure--a HERS rating of 100 represented a net zero energy home, while the reference home had a score of 80. There are issues that complicate converting old to new or new to old scores, but the basic formula is: New HERS index = (100 - Old HERS score) * 5. rating from HERS 55 to HERS 40 is a drop in a bucket compared to replacing a pool pump with a more efficient pump.”

“Buy a lot on an east-west street. East-west streets are better for passive solar design than north-south streets.”

“You want a centrally located air handler with short duct runs. I prefer an airtight all-metal duct system — no flex duct. You also want one centrally located tank-style water heater. That’s much better than three tankless water heaters. We stopped doing tankless water heaters.”

“Green building isn’t the stuff you add on after the design is done. And it is not about LEEDLeadership 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. points.”


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Image Credits:

  1. Martin Holladay