Building envelopes are most often of a layered construction,, the layers often consisting of insulation and masonry. This study investigates the influence of layer distribution and relative thickness of the insulation/masonry on the thermal behavior of the building and plant capacity. To evaluate this influence we have assumed that the overall thickness and the thermal transmittance (U value) of a three-layered building envelope are constant, but have varied the relative thickness and positions of masonry and insulation within the structure. Two structures were investigated: masonry/insulation/masonry, and insulation/masonry/insulation. The computer program BRE-ADMIT was employed; this program is based on the admittance procedure for analyzing building thermal behavior. Figures for the daily energy consumption in a single zone building together with the maximum power requirement are presented for the ranges of structures tested. It is shown that, for intermittent heating plant operation as opposed to intermittent cooling plant operation, the insulation/masonry/insulation structure saves 32-72% more energy compared with the masonry/insulation/masonry structure. For intermittent heating and cooling plant operation, a position can be found for the insulation layer within masonry/insulation/masonry structure, such that daily energy consumption is minimized but plant power requirement is maximized. Designers may find it helpful to be aware of these effects when designing buildings.