The extreme cold in the North can seriously affect the operation and performance of ventilation systems such as heat/energy recovery ventilators in residential buildings. Currently, single core heat/energy recovery ventilator (HRV/ERV) units are installed in Canada's North. At present, no HRVs/ERVs are designed or manufactured to meet the rigorous operation requirements in the Far North characterized by harsh climate and overcrowding.
The National Research Council (NRC) undertook a project in 2016, led by research Boualem Ouazia, to study technology innovations that can overcome problems faced by conventional single core HRVs/ERVs due to the frost formation in the heat/energy exchangers. The aim is to reduce operating failures of such units installed in the north, to improve the ventilation of northern homes (to meet the ventilation requirements set by the National Building Code and to reduce the energy consumption.
An alternative to conventional single core HRVs/ERVs is a novel dual core unit designed with either two parallel heat exchangers or two cores (sensible and enthalpy cores) in series. Such a design will address the frost buildup in the HRV/ERV units deployed in the harsh Arctic climate.
Two technologies with dual core design have been identified in collaboration with industry:
A dual core air handling unit is designed with a regenerative cyclic dual core heat exchanger, based on the cyclic storage and release of heat in the corrugated sheets alternately exposed to exhaust and intake air. It includes a supply and an exhaust fan and two cores filled with specially corrugated thick aluminum plates which act as heat accumulators. In between the cores is a patented damper section which changes over every 60 seconds to periodically direct warm air through one of the two cores while outside air gains heat from the heated aluminum plates in the other core. The technology does not require a defrost strategy or pre-heating system for application in harsh cold climates.
A dual core heat/energy recovery unit designed with sensible core and enthalpy core in series. The technology works by using one core as a pre-heat and the second as a booster. The configuration is designed to reduce the potential of core freeze-up. Outdoor air is brought through the pre-heat core first and then into the booster core; exhaust air passes through the booster core first and then through the pre-heat core. This allows moisture in the exhaust air to condense in the booster core and be drained away reducing the likelihood of freeze-up in the pre-heat core.
This research project was a rigorous investigation on the performance of innovative dual core design technologies. The methodology included the following:
Laboratory evaluation using NRC's climatic chambers to challenge the technologies with simulated indoor and outdoor conditions identified by CSA-C439 and in the North
Side-by-side testing using the twin houses of the Canadian Centre for Housing Technology, to compare the overall performance of a house operated with a dual-core unit versus a house operated with a conventional single-core ERV unit
Deployment and extended monitoring of the technology for proven performance, resilience and durability in harsh Arctic climate
The project is part of a larger effort to investigate, in collaboration with industry, innovative solutions for efficient ventilation of housing in the Arctic, ensure proper ventilation and at the same time minimize energy costs, and find the best ventilation technology to improve the indoor air quality in Northern housing and reduce its impact on the health of Northern communities.
Evaluation of the performance of a dual core air handling unit for use in cold climates. Report # A1-009461.1
Experimental comparison of performance between single and dual core energy recovery systems. Report # A1-009461.2
Evaluation of the performance of a dual core heat/energy recovery unit for use in cold climates. Report # A1-009461.3
Experimental comparison of performance between single core ERV and dual core heat/energy recovery unit – a side-by-side case study. Report # A1-009461.4