Freeze protection is the most important feature for hot water systems in cold climates. The most common types of systems installed in Colorado use antifreeze in the collectors. A combination of both strategies increases protection. There are passive systems available that do not require any electrical input - no pumps, no complicated controllers, no thermostats. They are completely self-regulating and low maintenance.
Some building codes require double wall separation if the solar heated fluid is non-potable.
Some pumped systems come with a small photovoltaic panel to power a DC pump. This eliminates the controller and enhances efficiency since solar collection fluid flow rates are consistent with available sun. Radiant floors or forced air production by fan coils sized to use low temperature water are two possibilities for such a system. If a building is to have future installation of active solar or photovoltaics, it should be designed ideally with large unbroken south-facing roof planes, at an approximate tilt of 45 o . Photovoltaic systems for buildings can be set up in two ways.