Energy Consumption in Mid- to High-Rise Residential Buildings Both Before and After Enclosure Rehabilitation

In completing a major study of energy use in mid- to high-rise multi-unit residential buildings (MURBs) in BC, it was noted that there were a number of unexpected or unusual aspects to energy usage in this type of building. For example, energy data that was provided by the electrical and gas utility contained anomalies. On roughly a monthly cycle the following energy data was provided: the suites’ electrical consumption (all suites together as one reading), the common areas electrical consumption (all common areas are provided as one reading), and gas consumption (usually from one meter reading). This data was correlated, normalized and then standardized in order to assemble annual and monthly records that were subjected to statistical analysis. Six building are presented as case studies, each having a minimum of two years of energy data both before and after a full-scale building enclosure rehabilitation (replacement of exterior wall, window and roof assemblies to address moisture related deterioration). They are compared from the standpoint of energy use – site energy only. These buildings were extracted from a larger study of 62 buildings. It is important to note that reducing energy consumption was not one of the primary design criteria for the rehabilitation. Rather, the primary design criteria were water penetration resistance and durability of the assemblies.

In doing a top-down assessment of each building the total energy use is known (as opposed to a bottom up approach where one has to know, assume or guess the consumption of each and every appliance or piece of equipment). Avoiding any assumption, one can arrive at monthly and annual estimates of suite electricity, common area electricity (elevators and other equipment, lighting, heating, etc.), and gas consumption (conditioning of ventilation air, domestic hot water, fireplaces, etc.). At the very least, a baseline amount and a variable amount of energy can be derived for each yearly period. This energy is for groups of end-uses and can be plotted against degree days or any other time or weather related axis. This paper presents an alternate energy analysis technique, and a number of conclusions can be drawn, some of them quite surprising when analyzing energy use in this manner. The analysis presented here complements the findings from the larger study where several alternate energy analysis techniques were used to analyze energy consumption end-use for each of the MURBs. This paper is best read in conjunction with the larger study report (RDH 2011).

This paper was presented at the 2011 Canadian Conference on Building Science and Technology.