National Building Research Institute, Technion, Haifa

In a series of previous research projects by Becker & Paciuk, optimal heating patterns were identified – according to specified criteria – for typical dwellings built with heavyweight elements. The profile of hourly electricity cost on which conclusions were based at that time characterized by only slight difference between day and night costs

(approximately a 2 to 1 ratio). This low ratio precluded obtaining any significant savings from shifting the heating period to hours of lower electricity cost. As for lightweight buildings, the absence of significant heat storage possibilities, coupled with the low day-tonight cost ratio, made the whole idea impracticable. Meanwhile, the proposed electricity cost profile has undergone changes (and still is), the tendency being to increase the day to night difference. Under these circumstances a clear-cut saving in energy cost can be expected from the shift of heating hours to periods of low electricity cost. even for lightweight buildings.

The specific aims of this research are:

I . To determine the effect of various electricity cost profiles on optimal heating patterns in conventional buildings by means of several cost effectiveness indices, in order to identify those cost ratios for which significant savings in energy costs could be obtained by shift in heating hours.

2. To investigate the effects of changing building components from heavy into lightweight elements (external envelope, internal walls,intermediate floors and roof) and to determine the corresponding optimal heating patterns.

3. To undertake a preliminary study of the possibilities of energy cost savings in public buildings by the shifting of cooling hours to periods of reduced electricity cost.

Stages 1 and 2 have so far been completed and results show that for both conventional and lightweight buildings significant savings in energy cost can be obtained with increased day to night cost ratios for those heating patterns that are based on two daily heating periods – 5 to 8 evening hours plus 1 to 8 early morning and night hours.