![]() ![]() Do not use gable vents because it's possible to draw rain and snow into the attic.Use only soffit vents as fresh-air intakes for powered attic ventilators.This formula assumes an eight-foot ceiling and takes into account typical unoccupied areas.Ī minimum of one square foot of inlet area for every 300 CFM of HVI-Certified fan capacity is required for proper fan operation. Be sure to include the "upstairs" area of multilevel homes. ![]() The required flow rate can be calculated by multiplying the gross square footage of the entire house (including unoccupied areas like closets) by 3. This flow rate will be great enough to create a perceptible "breeze" through the house. HVI recommends that a whole-house comfort ventilator have a minimum capacity to provide approximately one complete air change every two minutes within the occupied area. Local codes may require different continuous ventilation rates – always check with your building officials to determine the specific requirements for your area. Such needs could occur as a result of larger gatherings of people smoking a hobby or activity using paint, glues or other air-quality contaminants or for any other reason that requires additional ventilation to improve the quality of indoor air. In addition to this minimum, continuous ventilation rate, HRVs and ERVs often have additional capacity to provide higher ventilation rates to meet the occupants' needs. This rate can be more easily calculated by allowing 5 CFM per 100 square feet of floor area. This calculation must consider the complete occupied volume of the house. For optimum kitchen air quality, always use kitchen range hoods, kitchen fans or downdraft kitchen exhausters that vent directly outside the home.įor continuous indoor air quality ventilation, a heat or energy recovery ventilator (HRV or ERV) should provide 0.35 air changes per hour. Note: Nonducted, recirculation kitchen range hoods provide no actual ventilation. Selecting range hoods with HVI-Certified Performance Ratings will ensure that ventilation expectations and building code requirements are met. Inflated performance ratings are common for range hoods that are not HVI-Certified.For "professional-style" cooktops, HVI recommends following the cooktop manufacturer's advice to determine ventilation requirements.For hoods located over islands multiply the rate by 1.5.Kitchen range hoods equipped with multiple speed settings allow low-level, quiet ventilation for light cooking with the ability for higher rates when needed. ![]() When considering a downdraft kitchen exhauster, consult the range manufacturer's recommendations. They are an alternative when canopy style hoods are not desired due to location of the cooking surface and kitchen aesthetics however, their performance cannot equal that of hoods that capture the rising column of air above the cooking surface. Downdraft kitchen exhausters require a higher volume and velocity of air to adequately capture contaminants. Kitchen range hoods mounted above the range capture contaminants with their canopy shapes and exhaust them effectively with relatively low air volume. Recommended kitchen range hood ventilation rates vary greatly depending on the type of cooking performed and the location of the range.
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