Arkansas HVACR NewsMagazine January 2019

S tate, National, Chapter News Feature Story

ASHRAE defines mechanical ventilation as “…the active process of supplying air to or removing air from an indoor space by powered equipment such as motor- driven fans and blowers but not by devices such as wind driven turbine ventilators and mechanically operated windows.” Mechanical ventilation can be ambient air or tempered as with a Energy Recovery Ventilator, ERV. Either option must be filtered. Also, Arkansas Energy Code, AEC-2009, 403.5 requires that all mechanical ventilation must be automatic or gravity dampered. It is also important to note that ASHRAE 62.2-2016 2.1 “…considers chemical, physical, and biological contaminants that can affect air quality. Thermal comfort requirements are not included in this standard.” Acceptable indoor air quality is defined as “…air toward which a substantial majority of occupants express no dissatisfaction with respect to odor and sensory irritation and in which there are not likely to be contaminants at concentrations that are known to pose a health risk.” AHRAE 62.2-2016, Definitions Mechanical Ventilation may seem counter-productive to efforts to increase energy efficiency of the dwelling. It takes us to the question of why we make houses so tight that they need ventilation. The concept of energy efficiency is to save as much energy as possible. The concept of ventilation is to provide adequate oxygen for the occupants and to remove odors, humidity, and undesirable particulate. 62.2-2016

So, while there is an obvious dialectic, understanding the intent of both energy efficiency building and ventilation can provide the homeowner with the greatest comfort, lowest utility bill, and best health and safety environment through proper design of the interrelated structural, heating and cooling, and ventilation systems. It is far better to have an intentional balance of the needs. The next questions is, “ How much ventilation air is required .” There are two determinations: 1. Measured air infiltration, “…not less than 0.35 ACH” ASRAE 62.2, Table 405.5.2, Specifications For The Standard Reference And Proposed Designs, Air Exchange Rate, states, “For residences without mechanical ventilation that are tested in accordance with ASHRAE 119, Section 5.1, the measured air exchange rate but not less than 0.35 ACH.” The AMC 2010, Table 403.3, Private Dwellings also requires 0.35 but not less than 15 CFM per person. This standard provides that the tested Natural Air Changes per Hour should be no less that 0.35. NACH is the amount of air within the home that is exchanged with the outside air each hour. The most common way of determining this rate is conducting a blower door test. The problem with using this determination is a. the test can only be performed and NACH determined after a house is built and