3.1. Goal, benefits and problems

If the goal is to reduce dependency on non­renewable energy, at a certain point energy delivered from a solar thermal system becomes less expensive than energy saved from conservation measures, i. e. the marginal cost of the last increment of insulation or triple verses double glazing. Installing solar collectors or a pv system as part of a renovation is not always easy, however. Panels may be forbidden because they disturb the character of an historic village. Figure 5 shows the outline of the proposed and refused location for roof solar panels. The building commission allowed that the panels could be mounted on the shed to the rear, which, however is shaded by an old, noble nut tree.

Well done renovations drastically shorten the

heating season. A solar active system can then cover the minimal space heating demand of the spring and fall as well as the hot water demand, allowing other systems to be shut down for much of the year. This saves wear and extends component life spans. Two system types are reviewed here, a water system and an air system. Each has its special advantages for a given application.