Solar tiles can take the heat, and give it back


April 03, 1993|By James Dulley | James Dulley,Contributing Writer

QUESTION: The sun shines in my kitchen in the morning and in the dining room in the afternoon. It feels great. How can I save some of this free heat for the evening in the winter without overheating in the summer?

ANSWER: Installing solar tile on your floor or the lower part of the walls is effective, durable and attractive. It collects the sun's warmth during the day and slowly releases it in the evening. In the summer, the thermal mass of the tile and floor help reduce overheating.

Traditionally, certain types and colors of ceramic tile have been used for this purpose. These have the natural ability to efficiently conduct, store and reradiate the solar heat at night. Installing ceramic tile properly for passive solar heat is a simple do-it-yourself project.

For existing homes, you can lay it directly over your standard floor. Pouring a thin layer of cement first raises your floor only a little, but it greatly improves efficiency. For the highest efficiency, you should put the solar tile over a heavier masonry floor (ideal for new construction).

Today there are some attractive new earth-friendly tile alternatives to traditional ceramic tile. These products use recycled or cement-based materials to produce tile with good passive solar qualities and durability. They are available in a variety of finishes and colors.

The wide variety of shapes and sizes available in ceramic tile offer many design possibilities. For south-facing rooms especially, one alternative is to install tile on the walls as well as the floor. This increases the passive solar area and is very attractive as well.

When you select the tile, it is important to consider several solar energy properties of the specific tile and color: solar absorptance, emittance and thermal diffusivity and conductivity. Absorptance refers to the percentage of the sun's heat the material absorbs. I installed a dark brown tile in the entryway of my home. It has a higher solar absorbance than other tiles would.

Emittance refers to the tile's ability to release its stored heat back out into the room at night (when the temperature drops). Many materials readily absorb and store heat, but they don't emit it well.

Thermal diffusivity and conductivity both relate to the speed at which solar heat passes through the tile to the subfloor material. It also affects how fast the tile gives off the heat at night to warm your feet.

Correspondence should be addressed to James Dulley, c/o Baltimore Sun, 6906 Royalgreen Drive, Cincinnati, Ohio 45244.

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