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The paper explores the performance of a sub-slab ground heat exchanger, coupled to a heat pump, and the ability of the system to provide space conditioning and domestic hot water (DHW) for a multi-unit residential building (MURB) located in Ottawa, Ontario. The parametric analysis conducted to optimize the design of the building, as well as the sensitivity analysis performed to optimize the configuration of the sub-slab ground heat exchanger is also presented. According to the simulated results, the ground layer can store some of the rejected energy over medium term, without reducing the long-term performance of the heat pump. The annual energy consumption per dwelling unit (including heat pump, all auxiliary equipment, appliances, and lights) was estimated to be 28.4 GJ, significantly lower than the average annual energy consumption for a low-rise apartment in Canada (46.7 GJ per apartment). To assess the sensitivity of the system to environmental conditions, the simulation was conducted using the weather files for other five locations in Canada. [ABSTRACT FROM AUTHOR]

Simulation tools for predicting building thermal performance and solar system performance must accurately calculate solar irradiance to surfaces of arbitrary orientation. This is imperative to correctly predict passive solar gains to buildings and to accurately estimate thermal and electrical production of solar collectors. In cold climates, where snow covers the ground for long periods of time, ground reflected radiation can represent a substantial fraction of the total incident irradiance to highly tilted and vertical surfaces (e.g. windows). A new model has been developed to improve the calculation of ground-reflected radiation in simulation tools. The model is based upon empirical observations taken at a measurement site in Ottawa (Canada), and has been validated using disjunct data from the measurement site, and with published data from two other sites in the USA. The model was found to increase the accuracy of ground reflectivity predictions for cold and humid climates. [ABSTRACT FROM AUTHOR]