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This paper will present the context and application of earth tube systems for the provision of ventilative cooling and general make-up air in the heating, ventilation and air conditioning (HVAC) sector of the built environment; with a focus on case studies in Canada.
The first author has a background practising as a Chartered Engineer in both the UK and also in Canada and has been designing and optimising earth tube systems since 1998, with several case studies built in the UK and Canada on both domestic and commercial buildings of various uses. The first author is also undertaking a PhD, investigating the effectiveness of earth tube systems to temper outside air for supply to buildings located in British Columbia in Canada, where there is a in a Cordilleran climate with up to 40 degrees Celsius (°C) and cold snowy winters down to -30°C. This paper will focus on a built case study example that has been investigated as part of the first author’s PhD research in Canada. A discussion on methodology, drawn from the results of his case studies, to understand the safety and risks to health that need to be considered when using an earth tube system, especially to prevent mould growth and contamination in the pipe installation, is discussed. As is the different design approaches to earth tube systems for different building types, climate zones, occupancy loads and systems design are considered and evaluated.
The paper presents empirical monitored data from a case study that shows monthly temperature and energy performance of the earth tube system, over a period of one year for 2014. These results demonstrate how building code compliance (energy and ventilation) can be met or exceeded by the application of earth tube systems in the supply of ventilative cooling to buildings in the Canadian climate zone (Cordilleran). The extreme swings in seasonal air temperature impact upon earth tube system performance with interseasonal characteristics. The results presented and discussed are drawn from ground temperature sensors installed from ground level downwards to the underside of the earth tube level, in the case study building presented. The main conclusions drawn from this research show that before starting with an earth tube system design there are fundamental considerations which should be addressed. These include: climate zone, soil conditions, air flow, building occupancy patterns, HVAC system and Building Management System (BMS).
The studies show that once the above considerations have been addressed, then the potential for earth tube systems as part of a ventilative cooling strategy will be capable of meeting core demand for occupant comfort, without relying on conventional oil and gas fuelled HVAC systems. Thus, significantly reducing carbon emissions for cooling and space heating and energy costs.