Editing Heat recovery ventilation (section)

{{Short description|Method of reusing thermal energy in a building}}
{{Use dmy dates|date=January 2024}}
[[File:Ventilation unit with heat pump and ground - cooling.png|thumb|286x286px|Ventilation unit with heat pump & ground heat exchanger - cooling]]
'''Heat recovery ventilation''' ('''HRV'''), also known as '''mechanical ventilation heat recovery''' ('''MVHR''') is a [[ventilation (architecture)|ventilation]] system that [[energy recovery|recovers energy]] by operating between two air sources at different temperatures. It is used to reduce the heating and cooling demands of buildings.

By recovering the residual heat in the exhaust gas, the fresh air introduced into the air conditioning system is preheated (or pre-cooled) before it enters the room, or the air cooler of the air conditioning unit performs heat and moisture treatment.<ref>{{Cite book|title=An Encyclopedia of Architecture & Civil Engineering of China|last1=Zhongzheng |first1=Lu |last2=Zunyuan |first2=Xie |last3=Qian |first3=Lu |last4=Zhijin |first4=Zhao|publisher=China Architecture & Building Press|year=2000}}</ref> A typical heat recovery system in buildings comprises a core unit, channels for fresh and exhaust air, and blower fans. Building exhaust air is used as either a heat source or heat sink, depending on the climate conditions, time of year, and requirements of the building. Heat recovery systems typically recover about 60–95% of the heat in the exhaust air and have significantly improved the [[efficient energy use|energy efficiency]] of buildings.<ref name=":1">{{Cite journal|last1=Mardiana-Idayu|first1=A.|last2=Riffat|first2=S.B.|date=February 2012|title=Review on heat recovery technologies for building applications|journal=Renewable and Sustainable Energy Reviews|volume=16|issue=2|pages=1241–1255|doi=10.1016/j.rser.2011.09.026|s2cid=108291190 |issn=1364-0321|url=https://www.mdpi.com/1996-1073/12/7/1285/pdf}}</ref>

Energy recovery ventilation (ERV) is the energy recovery process in residential and commercial HVAC systems that exchanges the energy contained in normally exhausted air of a building or conditioned space, using it to treat (precondition) the incoming outdoor [[Ventilation (architecture)|ventilation]] air. The specific equipment involved may be called an Energy Recovery Ventilator, also commonly referred to simply as an ''ERV''.

An ERV is a type of air-to-air heat exchanger that transfers [[latent heat]] as well as [[sensible heat]]. Because both temperature and moisture are transferred, ERVs are described as total [[enthalpic]] devices. In contrast, a heat recovery ventilator (HRV) can only transfer sensible heat. HRVs can be considered ''sensible only'' devices because they only exchange sensible heat. In other words, all ERVs are HRVs, but not all HRVs are ERVs. It is incorrect to use the terms HRV, AAHX ([[air-to-air heat exchanger]]), and ERV interchangeably.<ref>The Healthy House Institute. Staff. "ERV". [http://www.healthyhouseinstitute.com/hhip_493-ERV Understanding Ventilation: How to Design, Select, and Install Residential Ventilation Systems.] 4 June 2009. 9 December 2009.</ref>

During the warmer seasons, an ERV system pre-cools and dehumidifies; during cooler seasons the system humidifies{{Request quote|date=February 2024}} and pre-heats.<ref name="Dieckmann1">Dieckmann, John. "Improving Humidity Control with Energy Recovery Ventilation." ''ASHRAE Journal''. 50, no. 8, (2008)</ref> An ERV system helps HVAC design meet ventilation and energy standards (e.g., [[ASHRAE]]), improves [[indoor air quality]] and reduces total HVAC equipment capacity, thereby reducing energy consumption. ERV systems enable an HVAC system to maintain a 40-50% indoor relative humidity, essentially in all conditions. ERV's must use power for a blower to overcome the pressure drop in the system, hence incurring a slight energy demand.<ref name="Dieckmann1" />