The IEA Annex 18 Demand Controlled Ventilating Systems-(DCV-Systems) with 9 participants are just in the middle of the work. Reviews are indicating energy conservation possibilities in the range of 8-40% in experiments and even more in theoretical studies. Most of the case studies will start this autumn with sensor tests, test room studies, and trials in occupied spaces. In the testrooms will be simulated the conditions in dwellings ---and offices with various ventilating systems. Almost 30 occupied buildings will be involved in tests in dwellings, offices, auditoria, and schools.
It was generally recognised that because of occupants' behaviour, natural ventilation rates were usually much lower than the accepted criteria for calculation. A great deal of anecdotal data existed which showed that frequency of opening windows bore a direct relation to external temperature and that the greater the volume the less the frequency of opening. The recent BRE survey also shows that very low ventilation rates, below 4 cubic metres/ person/hr have been found to be acceptable.
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