Conclusions

A solar air radiant heating system for a high-performance house must have thermal storage so that the heat release is delayed to the night hours. This is best provided as an integral part of the massive bearing construction of the house to minimize added costs. Typical solutions are to incorporate air channels in the floor (hypocaust) or masonry walls (murocaust). Good performance depends on a careful match between the collector size, storage capacity and rate of heat release, and heat demand of the house. The latter is especially true for high-performance houses. Over-dimensioning the system can result in overheating and low efficiency. In middle Europe, the useful heat contribution over the heating season of a well-designed system can lie between 50 and 300 kWh/m2/collector. Finally, and importantly, such a system must be coupled to the DHW production in order to be economical. A reduction of up to 60 per cent in the energy for hot water production is then possible. The economics are still further improved if the hypocaust or murocaust system is designed in this way and is used to provide the further benefit of summer cooling.

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