Most of our customers require at least a portion of their solar thermal system to be covered at one point in year. If you are using system for pool heating, most customer cover collectors when the pool is shut down in winter. If you are only using solar system for space heating, most customers will cover up some collectors in summer. You do not have to cover up collectors if you have a constant and reliable dumping source for energy (outdoor dissipation loop, pool, hot tub, hot water, storage tank dump). The requirement for covering up collectors is only if you do not have enough heating demand for the supply you are producing with solar system.