How efficient is your HRV? | Ask A Builder – Alaska News

How efficient is your HRV? | Ask A Builder – Alaska News

FAIRBANKS — Heat recovery ventilators, or HRVs, provide mechanical ventilation to the whole house by using warm, exhaust air to preheat fresh, incoming air. Because they recover heat from indoor air, they result in more comfortable temperatures than ventilation systems that just bring in cold outdoor air. They also are more efficient.

The HRV core allows heat to transfer to the incoming air without the airstreams mixing. The warmed fresh air is then distributed throughout the home using ducts and circulating fans while exhaust air is vented outside. How well an HRV is able to pre-heat the supply air depends on several factors: the temperature of the indoor air, the temperature of the outside air, the flow rate through the HRV and the HRV’s efficiency.

More efficient HRVs are able to recover more heat from the exhaust air and transfer it to the supply air.  When comparing the efficiencies of HRV models, it is important to understand efficiencies may be listed differently by the manufacturer and may be calculated differently as well. Additionally, these efficiencies vary depending on the difference between indoor and outdoor temperature and the flow of air through the HRV.   

The sensible recovery efficiency (SRE) quantifies the amount of heat recovered by the incoming fresh air from the exhaust air. It is reported as a percentage of the total heat available for recovery. For instance, if an HRV has an SRE of 55 percent for a given flow rate and temperature difference, this means the HRV core transfers 55 percent of…

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