Editing Ventilation (architecture) (section)

== Ventilation rates for indoor air quality ==
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The ventilation rate, for commercial, industrial, and institutional (CII) buildings, is normally expressed by the volumetric flow rate of outdoor air, introduced to the building.  The typical units used are [[Standard cubic feet per minute#Cubic feet per minute|cubic feet per minute]] (CFM) in the imperial system, or liters per second (L/s) in the metric system (even though [[cubic meter per second]] is the preferred unit for [[volumetric flow rate]] in the SI system of units).  The ventilation rate can also be expressed on a per person or per unit floor area basis, such as CFM/p or CFM/ft², or as [[air changes per hour]] (ACH).

=== Standards for residential buildings ===
For residential buildings, which mostly rely on [[Infiltration (HVAC)|infiltration]] for meeting their ventilation needs, a common ventilation rate measure is the air change rate (or air changes per hour): the hourly ventilation rate divided by the volume of the space (''I'' or ''ACH''; units of 1/h). During the winter, ACH may range from 0.50 to 0.41 in a tightly air-sealed house to 1.11 to 1.47 in a loosely air-sealed house.<ref>Kavanaugh, Steve. Infiltration and Ventilation In Residential Structures. February 2004</ref>

ASHRAE now recommends ventilation rates dependent upon floor area, as a revision to the 62-2001 standard, in which the minimum ACH was 0.35, but no less than 15 CFM/person (7.1 L/s/person). As of 2003, the standard has been changed to 3 CFM/100 sq. ft. (15 L/s/100 sq. m.) plus 7.5 CFM/person (3.5 L/s/person).<ref>{{cite web|title=ASHRAE's First Residential Ventilation Standard|url=http://epb.lbl.gov/Publications/lbnl-54331.pdf|publisher=[[Lawrence Berkeley National Laboratory]]|author=M.H. Sherman|archive-url=https://web.archive.org/web/20120229082915/http://epb.lbl.gov/Publications/lbnl-54331.pdf|archive-date=February 29, 2012}}</ref>

=== Standards for commercial buildings ===
=== Ventilation rate procedure ===
Ventilation Rate Procedure is rate based on standard and prescribes the rate at which ventilation air must be delivered to space and various means to the condition that air.<ref name="ASHRAE Standard 62">ASHRAE Standard 62</ref> Air quality is assessed (through CO<sub>2</sub> measurement) and ventilation rates are mathematically derived using constants.Indoor Air Quality Procedure uses one or more guidelines for the specification of acceptable concentrations of certain contaminants in indoor air but does not prescribe ventilation rates or air treatment methods.<ref name="ASHRAE Standard 62" /> This addresses both quantitative and subjective evaluations and is based on the Ventilation Rate Procedure. It also accounts for potential contaminants that may have no measured limits, or for which no limits are not set (such as formaldehyde off-gassing from carpet and furniture).