The paper examines the extent to which user's intervention may compromise the thermal performance of small sunspaces in the context of a Solar Energy Demonstration Project at Easthall in Glasgow (55°52′N), which was monitored from September 1992 to May 1994. Results indicate a tendency to close down windows etc, late in autumn and open them up early in spring relative to heat demand. In other words a user-driven energy load due to ventilation is higher in autumn and spring than in the central winter period. However, effective rate of ventilation, taking account of the preheat effect of the glazed spaces, is found to be more steady over an entire heating season. Thus, inclusion of glazed buffers has been shown to lessen the thermal burden of window opening in autumn and spring; while saving in winter due to preheated air for ventilation tends to be slightly higher than predicted. Results also indicate that amount and frequency of opening/ventilation relates to specific social and occupancy characteristics; and that some users were able to trim their energy load by better use of the controls at their disposal in the second season. As a by-product, the monitoring has shown that energy models which take a steady rate of ventilation over a heating season are unrealistic.