Editing Heat recovery ventilation (section)

==Energy recovery ventilation==

=== Importance ===
Nearly half of global energy is used in buildings,<ref>{{cite web |url=http://www.interacademycouncil.net/CMS/Reports/11840/11914/11920.aspx |title=2.3 The buildings sector - InterAcademy Council |website=www.interacademycouncil.net |url-status=dead |archive-url=https://web.archive.org/web/20080601164314/http://www.interacademycouncil.net/CMS/Reports/11840/11914/11920.aspx |archive-date=2008-06-01}}</ref>{{Obsolete source|date=February 2024}}and half of heating/cooling cost is caused by ventilation when it is done by the "open window" method {{definition needed|date=July 2022}} according to the regulations{{citation needed|date=July 2022}}. Secondly, energy generation and grid is made to meet the peak demand of power. To use proper ventilation; recovery is a cost-efficient, sustainable and quick way to reduce [[global energy consumption]] and give better indoor air quality (IAQ) and protect buildings, and environment.{{citation needed|date=January 2024}}

=== Methods of transfer ===
During the cooling season, the system works to cool and dehumidify the incoming, outside air. To do this, the system takes the rejected heat and sends it into the exhaust airstream. Subsequently, this air cools the condenser coil at a lower temperature than if the rejected heat had not entered the exhaust airstream. During the heating seasons, the system works in reverse. Instead of discharging the heat into the exhaust airstream, the system draws heat from the exhaust airstream in order to pre-heat the incoming air. At this stage, the air passes through a primary unit and then into the space being conditioned. With this type of system, it is normal during the cooling seasons for the exhaust air to be cooler than the ventilation air and, during the heating seasons, warmer than the ventilation air. It is for this reason the system works efficiently and effectively. The [[coefficient of performance|coefficient of performance (COP)]] will increase as the conditions become more extreme (i.e., more hot and humid for cooling and colder for heating).<ref>Braun, James E, Kevin B Mercer. "Symposium Papers - OR-05-11 - Energy Recovery Ventilation: Energy, Humidity, and Economic Implications - Evaluation of a Ventilation Heat Pump for Small Commercial Buildings." ASHRAE Transactions. 111, no. 1, (2005)</ref>

=== Efficiency ===
The efficiency of an ERV system is the ratio of energy transferred between the two air streams compared with the total energy transported through the heat exchanger.<ref name="Pulsifer1">Pulsifer, J. E., A. R. Raffray, and M. S. Tillack. "Improved Performance of Energy Recovery Ventilators Using Advanced Porous Heat Transfer Media." UCSD-ENG-089. December 2001.</ref><ref name="christiansenbook">Christensen, Bill. [http://www.p2pays.org/ref/20/sourcebook/www.greenbuilder.com/sourcebook/EnergyRecoveryVent.html#EFFICIENCY "Sustainable Building Sourcebook." City of Austin’s Green Building Program. Guidelines 3.0. 1994.] {{Webarchive|url=https://web.archive.org/web/20110928092442/http://www.p2pays.org/ref/20/sourcebook/www.greenbuilder.com/sourcebook/EnergyRecoveryVent.html#EFFICIENCY |date=28 September 2011 }}</ref>

With the variety of products on the market, efficiency will vary as well. Some of these systems have been known to have heat exchange efficiencies as high as 70-80% while others have as low as 50%. Even though this lower figure is preferable to the basic HVAC system, it is not up to par with the rest of its class. Studies are being done to increase the heat transfer efficiency to 90%.<ref name="Pulsifer1" />{{Obsolete source|date=February 2024}}

The use of modern low-cost gas-phase heat exchanger technology will allow for significant improvements in efficiency. The use of high conductivity porous material is believed to produce an exchange effectiveness in excess of 90%, producing a five times improvement in energy recovery.<ref name="Pulsifer1" />{{Obsolete source|date=February 2024}}

The Home Ventilating Institute (HVI) has developed a standard test for any and all units manufactured within the United States. Regardless, not all have been tested. It is imperative to investigate efficiency claims, comparing data produced by HVI as well as that produced by the manufacturer. (Note: all units sold in Canada are placed through the [[R-2000 program]], a standard test equivalent to the HVI test).<ref name="christiansenbook" />{{Obsolete source|date=February 2024}}