Buildings
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A Low-Cost, Healthy Plan for Ventilation One of the exciting outcomes of Advanced Energy's work with designers and builders of lower cost homes is the discovery of an effective ventilation system that comes at a cost of less than $200. Over the past year, Advanced Energy has worked to extend the benefits of the SystemVision™ Home Guarantee program to low- and moderate-income housing. Twenty-two non-profit builders and developers, including Habitat for Humanity affiliates and community development corporations across the state of North Carolina, are now engaged in this program. Funded by the NC Community Development Initiative and the NC Housing Finance Agency, the program assures that the homes built by participating groups meet the ten standards of Advanced Energy's SystemVision program and will not exceed a predefined level of energy usage. Plans are already underway for at least 350 homes to be constructed next year by these builders, with plan review, contractor training, quality control, and performance testing to be performed by Advanced Energy staffers. SystemVision — A Juggling Act That Works Bill Klotz, Project Manager of the Affordable Housing at Advanced Energy, explains that the low-cost ventilation strategy emerged from trying to satisfy two of the SystemVision program standards — house air-tightness and fresh air ventilation. SystemVision requires that houses be even tighter than the current industry norm — a requirement at odds with getting fresh air into the house. (That's the whole point behind SystemVision. Treating the house as a system means constantly juggling all ten program standards to achieve the best results!) In homes built years ago, air handlers run fairly frequently, drawing unconditioned air in from leaks in the house's exterior shell — and often enough some not-so-healthy air from the crawl space or attic. When houses are very tight, the air handler runs less and energy usage is low, but the air can grow staler and unhealthier by the hour and by the day. A Simple Two-Part System Does the Trick So where is a house supposed to get its air? Part one of this new low-cost ventilation strategy is simply running a duct from the outside of the home to the air handler to create a source of fresh air. Naturally, the outside opening needs to be covered with screen to prevent entry of foreign matter. In most cases, this means creating a duct that runs straight from the air handler to the nearest logical exit point in the house shell. However, care must be taken not to draw in air from an undesirable source. For example, the duct intake should not be located near a clothes dryer vent or gutter downspout, close to an odor source such as a dog pen, near an area where puddles might develop, or close to a vent stack if the duct intake is on the roof rather than in the foundation. The second part of the challenge is making the house periodically take a breath of fresh air when inside temperature changes aren't triggering the air handler to run. This is solved by attaching a small controller to the air handler that keeps up with when the air handler last ran, and prompts it to run if it hasn't done so in the last 20 minutes. It also prevents the air handler from coming on for several minutes after the compressor has shut off, eliminating the problem of reintroducing moisture from the wet coil back into the house. This patented electronic device, called an AirCycler® and produced by Lipidex Corporation, is available for less than $100. It was invented by Armin Rudd, formerly of the Florida Solar Energy Center and currently with Building Science Corporation. At a total cost of less than $200, this simple two-part system merits consideration not only in lower-cost homes, but also in higher-end construction. It's a small price to pay for improving the health and safety of home occupants! More Information |