We’ve been planning this test for a while now and we finally had a chance to run it. Since the workers took off for Songkran, they’ve been busy with other things.

But we finally got a simple sprinkler on the roof of BaanMae.

Our main goal here was just to do a feasibility test of the idea of using sprinklers on the roof to cool the roof.

First, I measured the ambient temperature of the floor of the balcony at about 35C:

Next I measured the temperature of the underside of the balcony roof (where there was no insulation) at over 70C:

Finally, I connected the row of sprinklers on the balcony roof to a garden hose for testing and ran it at a low setting for about 5 minutes. The roof temperature dropped to about 39C, for a temperature drop of over 30C!

Given that the ambient temperature in the shade was only 35C, that is an under roof temperature drop of about 90% relative to ambient temperature in the shade!

This is much more effective than I was expecting. The next step will be to connect the water supply for the sprinklers to DC pumps in the collected rainwater cistern. This will mean we can use a small amount of renewable solar power (maybe 20-30W average) and a small amount of reclaimed rain water to reduce the amount of heat entering the house (or radiating down to the balcony) through the roof by about 90%. And because we are reducing the temperature differential between roof and room, this reduction of heat flow into the house is above and beyond reductions due to insulation.

For my goal of comfortable tropical living without air conditioning, this is a very promising result indeed.