To cool a shed having a corrugated iron span roof, line the under side of the latter with a material which resists the passage of heat through it. Hair felt in sheets A in. thick is commonly used. Silicate cotton is better, but not so easy of application. Still further to cool the interior a regular current of air is necessary, and this can only be obtained by an active chimney or a mechanical air propeller. A change of air and the escape of vitiated air can be obtained by having an opening at each end of the shed, one near the ground and one near the roof.