Long-term performance and resiliency testing of a dual core energy recovery ventilation system for the Arctic

The Arctic environment is challenging for housing ventilation and heating systems. Energy consumption and demand for space heating for northern remote community residential buildings are very high. Airtight built northern homes require energy efficient and effective ventilation systems to maintain acceptable indoor air quality and comfort, and to protect the building envelope from moisture damage. Conventional single core heat/energy recovery ventilation systems are a mature and proven technology for modern and energy-efficient Canadian homes; but underperform and are plagued with problems when operating in high-arctic locations north of 60°. Their performance achieved to date has been inadequate due to equipment failures (freezing of cores, etc.) and their defrost strategies can undermine ventilation rate requirement and the energy saving. Inadequate ventilation in northern communities contribute to poor indoor air quality, and this contribute to increased cases of serious health issues;  tuberculosis and asthma, specifically asthma infections among young Inuit children.  To overcome these issues, a novel dual core energy recovery system designed with two heat exchangers could address frost protection by periodically directing warm air through one core of the two cores while outside air gains heat from the other. By employing a cycling heat exchanger, frost doesn’t have a chance to form, and one heat exchanger is always delivering conditioned air to the space. This paper presents results from a repeated side-by-side winter testing using NRC’s twin research houses comparing whole house performance of a reference house equipped with a single core ERV with a test house equipped with a dual core energy recovery unit, and some results from the long-term monitoring of the technology deployed in a triplex located in Canada’s Arctic. The side-by-side testing was undertaken in the NRC twin-houses research facility of the Canadian Centre for Housing Technology (CCHT) over four weeks in winter 2019. In comparison with a conventional single core ERV, the dual core energy recovery system had much higher apparent sensible effectiveness, a difference of 12 percentage points, and had much higher apparent total effectiveness, a difference of 9 percentage points. The dual core design showed no sign of frost problems after 4 weeks of testing and continued to provide outdoor air throughout winter days without stopping to defrost, unlike the conventional single core ERV which had to spend up to 7.5 hours defrosting per day.  It also provided a higher supply air temperature (up to 3°C) to indoor and the house with dual core ERV had a whole-house heating and ventilation energy saving of 5% over the winter testing period. The long-term performance testing was undertaken in a mechanical room of a triplex on the Canadian High Arctic Research Station (CHARS) in Cambridge Bay (Nunavut) to assess the resiliency and durability of the technology in harsh cold climate. The monitoring period included two heating seasons 2017-18 and 2018-19 and showed that the dual core technology was very frost-tolerant and capable of withstanding temperature below -40°C for long periods without deteriorating its thermal and ventilation performances, and providing constant and continuous supply of outdoor air. The proven performance and resiliency to harsh Arctic operating conditions demonstrates that the dual core design ERV is a solution to ventilation of northern housing, in providing continuous ventilation that will improve indoor air quality and health in Northern communities.