Greenhouses have been used extensively for growing agricultural products including vegetables, fruits, flowers and other indoor plants where a narrow range of desired temperature is required for the viable biological processes of plants. When the interior temperature of the greenhouse is outside the range, the plants can suffer from irreversible loss or die. It is not critical, however, to control the relative humidity inside an agricultural greenhouse as long as sufficient moisture is supplied to the soil. It is undesirable to remove much moisture from an agricultural greenhouse because extra water would be provided to the soil or the plant would be dehydrated.