The energy benefits of sunspaces in houses with ventilation heat recovery.

A heat recovery system reclaims heat from outgoing stale air, supplying it to incoming fresh air. The energy benefit is greatest if it supplies all the fresh air to the house and none enters via uncontrolled openings, hence ventilation heat recovery (VWR). A sunspace (or conservatory) attached to a dwelling will almost always be at some temperature above ambient. Heat losses by conduction through the adjacent building fabric and ventilation losses via cracks will be reduced. This effect is modest; however, Baker [1] has proposed that drawing ventilation air from a sunspace can save substantial amounts of energy, provided ventilation can be preferentially drawn from the conservatory rather than through adventitious openings throughout the dwelling. In a CEC Demonstration Project, the authors are using a variety of mechanical systems and retrofit conservatories to examine the benefits of such systems. Data is presented which shows that the combination of VHR with sunspaces does not maxirnise the benefits of either, A variety of strategies is presented which attempt to optimise this combination - they illustrate the flexibility of the simulation model used; but do not succeed in justifying the sunspace/VHR combination. However, the study has shown that energy is available by heat pumping on the VHR exhaust. Attention is also devoted to sunspace design parameters; glazing type is shown to have a considerable effect on sunspace temperature.