Paper Conference

Proceedings of eSim 2012: 7th Conference of IBPSA-Canada


Design Methodology Embodying the Energy and Economic Performance of Solar Houses

Ted Kesik, Liam O'brien

Abstract: The process for efficiently designing solar houses (a.k.a. low energy houses, in some cases net-zero energy houses) has significantly advanced with the development of early-stage (conceptual) design tools. Ecos is a conceptual energy modelling tool for solar houses that deploys the EnergyPlus computational engine. The functionality of Ecos was defined as a result of a survey of the suitability of existing tools to perform conceptual design for low energy houses, wherein it was determined that two major weaknesses were: 1) they lacked the ability to accurately model many passive and active solar features; and 2) they targeted detailed design that required over-specification of house features. In Ecos, only the variables that have a significant impact on energy performance need to be considered by the user, allowing for some other variables users like to have control over even if their interactions are not very significant. This software enables a large number of interdependent performance variables to be combined and arranged to achieve a desired net energy use target. However, the design software is not yet capable of assisting the user to identify the most cost effective among a large number of alternative with similar levels of energy and comfort performance. This paper presents a general methodology for considering energy and economic performance at the early design stage, and then goes on to demonstrate how it can be applied within a specific context. In this example, an archetype house representing the typical characteristics of new houses built in Ontario is selected as the reference house for comparative assessments. It embodies energy conservation measures that reflect the prescriptive requirements of the Ontario Building Code in terms of building envelope components and HVAC system equipment. A life cycle cost over a 25-year study period, corresponding to a normative amortization period, can be calculated for this reference house using the Modified Uniform Present Worth measure that accounts for the discount rate and the energy escalation rate. Only its life cycle energy costs are considered because as the Code minimum, it is assumed to have a capital cost of zero in relation to alternatives with upgraded energy conservation measures. Greenhouse gas emissions may also be assessed as these have economic implications, albeit unresolved at present in Ontario. By combining energy and economic analyses at the schematic design stage, it is possible to identify a combination of energy conservation/generation measures that deliver a cost effective solar house-as-a-system.
Pages: 230 - 242