Ventilation/Cooling Method Needs User Input
 
Ventilation/Cooling Method Needs User Input

Many U.S. homebuilders and buyers view compressor cooling as a necessity, even in mild climates. But the widespread use of compressor cooling causes several problems, especially in warmer regions like the West Coast. It is largely responsible for summer peak loads that are expensive for utilities to serve.

Studies have shown that building energy-efficient homes and ventilating them with cool night air can significantly reduce air conditioner size and summer energy use. In many areas of the country, especially the West and Northwest, houses with efficient windows, slightly above standard insulation, and exposed thermal mass can be ventilated with outside air to significantly reduce or eliminate cooling load.

Whole-house cooling fans are one popular way to provide mechanical night ventilation cooling (see "Finding the Whole-House Fan That Fits," p. 17). However, they do have several drawbacks. Whole-house fans do not filter out dust and pollens. They do not properly distribute ventilation air to each room, and they also require that windows be opened, compromising security.

Our Alternatives to Compressor Cooling (ACC) project is currently developing an alternative nighttime cooling system that is integrated with filtered ventilation air. We want to demonstrate to homebuilders and buyers that houses built with no (or reduced) compressor cooling can be comfortable, practical, and marketable.
Night VentilationThrough careful integration of architectural and mechanical design features, ACC researchers have developed two designs for houses that ventilate with filtered air. One house design is for locations in milder California climates and requires no compressor cooling; the second is for hot climates and calls for substantially reduced compressor cooling and air conditioner sizing. Both designs depend on a combination of reduced heat gain, adequate thermal mass, and nocturnal cooling.

The designs rely on a nocturnal ventilation technique that combines an outdoor air intake damper ("economizer") with a residential air handler or furnace. This technique delivers filtered outdoor air to each room, without compromising security. The brain of the system is located in a smart thermostatic control.

When the home is optimized for ventilation cooling, the maximum indoor temperature is largely a function of the minimum nighttime outdoor temperature, glazing orientation, and glazing exposure. If interior mass can be cooled to a low temperature through night ventilation, the following day's maximum indoor temperature will be lower. The ACC thermostat uses information it has stored about the house's thermal behavior to anticipate how much night cooling it needs to "beat the heat" the following day. Because the cooling scheme is based on temperature swings, the ACC system design calls for owners to accept a "comfort zone" (for example, between 65¡ãF and 78¡ãF) rather than striving for the standard fixed thermostat "setpoint."
Help Design the ACC Thermostat!We need your help. Currently, our team is developing a user interface for the thermostatic control. The interface must effectively convey the concepts of night ventilation cooling to the user and provide optimal control. Our first prototype is on the Web and really works. Please visit www.davisenergy.com/acc and give the prototype a test run. We look forward to your comments and suggestions!

The ACC research team is led by George Loisos, Architect, and the Davis Energy Group. It includes researchers from U.C. Berkeley, U.C. Davis, and Lawrence Berkeley National Laboratory. For more information on the ACC project, contact Leo Rainer, Davis Energy Group, Davis, California; Tel:(530)753-1100, E-mail: lrainer@davisenergy.com.