Phase Change Interior Walls Save Household Energy

If the walls of your house could absorb and release heat to maintain a constant indoor temperature -- without using outside energy sources -- your heating and cooling bill would be lowered. And overall energy demands to the grid and to fossil fuel resources such as natural gas, propane, and fuel oil would be lower. Here is the approach that BASF is taking to do just that:

Building materials that absorb heat during the day and release it at night, eliminating the need for air-conditioning in some climates, will soon be on the market in the United States. The North Carolina company National Gypsum is testing drywall sheets--the plaster panels that make up the walls in most new buildings--containing capsules that absorb heat to passively cool a building. The capsules, made by global chemical giant BASF, can be incorporated into a range of construction materials and are already found in some products in Europe.

The "phase-change" materials inside the BASF capsules keep a room cool in much the same way that ice cubes chill a drink: by absorbing heat as they melt. Each polymer capsule contains paraffin waxes that melt at around room temperature, enabling them to keep the temperature of a room constant throughout the day. The waxes work best in climates that cool down at night, allowing the materials inside the capsules to solidify and release the heat they've stored during the day.

In some southern European climates, for example, the materials absorb enough heat during the day to save 20 percent of the electricity needed for air-conditioning. In northern Europe, where nighttime temperatures are cooler, a building incorporating the materials may not need an air conditioner at all, says Peter Schossig, an engineer at the Fraunhofer Institute in Munich, Germany, whose research group worked with BASF to develop the capsules. _TechReview

This type of passive environmental control should be able to reduce 30% or more of household temperature control expenses, when developed fully.