The space heating energy needed during the winter heating season in Seattle Washington, USA, was monitored over a 15 year period, 1987–2002. Single family residence houses were constructed to building code standards in force at the time of construction and two more to standards calling for envelopes with improved thermal resistance. Although space conditioning energy needs are strongly affected by occupant behavior, simulations generally ignore the temporal occupant behavior in estimating the energy needed for heating and cooling. Vigorous conservation tactics, which produce a thermal response that is highly transient, can lead to substantially different energy needs. No correlation could be established from the measured space heating when aggressive conservation made use of thermostat setback at every opportunity. In this paper we investigate the effects of occupant behavior and the effect of temporal solar heating of walls in the Seattle area for improved thermal construction.