Cool Clay

Laboratory
Experiment: Cool Clay

During a March 2006 SEED workshop in Malaysia, we visited Badan Warisan Malaysia, the Heritage Centre for Malaysia, in Kuala Lumpur. On the grounds is a traditional Malay house, built in sections during the 1920s and 1930s. The house originally belonged to a local headman, but the family no longer used it, and it sat vacant. The house was moved to the Heritage Centre in the mid-1990s, where it was restored. Rumah Penghulu Abu Seman opened to visitors in November 1997.

This traditional house lacks electricity for air-conditioning or fans. So how did the family keep the house cool in the hot Malaysian climate? The clay tile roof helped. Here’s how:

When it rains, the clay absorbs water. When the rain stops, the water evaporates, cooling the roof and the air under it. This is called “evaporative cooling.” At a subsequent workshop we decided to do an experiment to see if evaporative cooling can really cool a building.

Our Experiment

Tools and Materials

We found some roof tiles, but they turned out to be concrete, not clay. However, we decided to test them anyway. We still needed to use clay, so we found a broken clay flowerpot. Our materials were:

• 2 concrete roof tiles

• 2 pieces of clay flowerpot

• 4 thermometers

What To Do 1. We soaked one concrete tile and one clay piece in water for about 10 minutes.
2. Then we put all four pieces—the wet tile, the dry tile, the wet piece of the flower pot, and the dry piece—on the ground in the sun with a thermometer under each one. The thermometers all registered the same temperature of 36°C (96.8°F).
3. We assigned one person to each of the four pieces. A fifth person kept track of the time. At the end of 1 minute, we lifted the tiles, read the temperatures, and recorded the data on a piece of paper. We then put down the tiles again. We did this at 1-minute intervals for 6 minutes.

		Digging Deeper
		Find out more about
	why evaporation causes cooling…

What did we find?  Take a look at our results.

Now it is your turn to try this experiment. You can use the same materials we used, and you can add in other common roofing materials, including tar-paper shingles, wooden shingles, slate tiles, or metal roofing.

What were your results?

Further Experiments

Other factors can influence temperature. To further this experiment, you can try a number of variations.

• Keep the clay tile wet over a longer period of time and see how that affects temperature.
• Try the experiment at night when there is no direct sun on the tiles.
• Try the experiment on a cloudy day.
• Check the relative humidity and see how humidity affects evaporative cooling.