My bride and I spent yesterday, Saturday, at an all-day seminar (8:30 am to 4:30 pm) to learn about building a green home. We heard some surprising things. First, Austin was the first city to have a green building program. Starting in 1985, the program resulted in the Energy Star program now used by the feds, and the green rating used by the city served as the inspiration for LEED certification (Leadership in Energy and Environmental Design). Impressive. As might be expected from such an influential program, the day’s seminars were also quite impressive and informative—as well as entertaining and inspiring.
Some (appropriately shaded and low wattage) highlites:
- Design for passive solar. Seems like a “duh” kinda deal, but most houses do not consider the sun in their design. Developers are more concerned about getting the house built, looking good, and sold rather than operating good. The city architect’s point was that how the house was designed with respect to the sun was the single most important “green” item to think about. Such houses use far less energy than houses dolloped onto lots with no solar consideration. I have to confess that I was fixated on active solar rather than passive before learning this. I’m happy to report that I am now solarly passive aggressive.
- Strawbale, adobe, and rammed earth aren’t good choices for Austin. These building techniques rely on large diurnal temperature swings to work their magic. Aside from earlier this week and the occasional blue norther, Austin doesn’t get those swings. Therefore, the thermal loading works against you in our nonswinging climate. Not that we were considering these building techniques, but they are definitely off the table now.
- In Austin, air conditioning in the big energy hog. Therefore, anything to lower cooling costs is paramount for lower energy consumption. There’s the aforementioned passive solar considerations (design for windows to be shaded in the summer but sunned in the winter), but there’s also the design of the central air system. AC contractors tend to oversize units (no one has ever been sued for oversizing a unit), but that increases electric usage and decreases dehumidifying. Also, architects don’t usually consider where the ductwork is going to go. The straighter the duct work, the more easily the air flows, the more efficient the system, the less tonnage you need, the less energy you use, the more money you save. Put the air handler and the ductwork inside the conditioned space of the house—You don’t have to worry about leaks (and cooling the attic) that way. The HVAC engineering guy gave one of the most entertaining and informative presentations of the day. He was awesome.
- The typical goal for an HVAC system is to have the ACH (air changes per hour) less than 0.5. This means that half the air in your house is replaced with air from outside your conditioned space every hour. Say what?!?!? On one hand, maybe this is a good thing: Nobody wants to breathe stale air. On the other hand, that’s a lot of hot air your house is pulling in and subsequently having to cool during the summer. If your house was perfectly sealed, an ACH of 0.5 means you have a hole 10 inches by 12 inches in it. Progressively sealed houses get down to 0.3. Hyper-sealed houses get down to 0.1. I reckon our current house is over 1.0…
- You need to run the vent in your bathroom for at least 30 minutes after you take a shower. It’s critical to get that moisture out of your house. It saves you in the long run.
- The vent over your stove is to remove heat, not smells or greasy air. Always have it on when your stovetop or oven is hot.
- Geothermal may not be such a good idea in Austin. Installers call it geothermal, but it’s actually a heat pump using the earth as a heat sink (in summer) or a heat source (in winter). Usually, these systems use boreholes drilled some 150 feet into the subsurface, one borehole per ton of cooling. What is happening is that the ground is warming up from the heat exchange during the summer months but, because our winters are so mild, the system is not bleeding off the heat enough during the winter months. Therefore, the ground is slowly heating up year after year decreasing the efficiency of the system. We were thinking about geothermal; we’re not thinking about it anymore.
- Heat pumps work well in Austin, but they fail to heat your house when temperatures fall below 37 degrees. The back up heating in these systems, electric strips, use a lot of power. On balance, a good idea, but pray for global warming.
- Your ceiling fans need curved blades.
- Solar water heating may not make sense for just two people.
- Annual heating and cooling loads should be 1 to 1.25 kilowatts per square-foot. Our current house, at 1,000 square feet, should have a load of 1,100 to 1,375 kilowatts. It actually has ranged between 5,600 to 8,700 kilowatts over the past four years. Ouch. That's what a 100 year + house gets you.
- Electric generation by solar runs about six bucks a watt.
- IKEA cabinetry is free of formaldehyde.
- Austin is not a good place for personal wind generation.
- There are some crazy women that go to these things.
- And finally, through good design choices and good building, it’s possible to build a net-zero “capable” home.
So there you have it. Highly recommended if you are interesting in attending and useful to anyone from around the country.
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