Spot ventilation standards
How much ventilation does your home need? There's no need to guess. Building professionals know the guiding standard for residential ventilation design is ASHRAE 62.2, the residential ventilation standard developed and maintained by the American Society of Heating, Refrigeration and Air-Conditioning Engineers (ASHRAE). The city where you live may base its building codes on this standard.
This standard tells you how to figure the baseline requirements for spot ventilation for bathrooms and kitchens.
Under ASHRAE 62.2 the main requirements are:
(1) Whole house mechanical ventilation to maintain acceptable air quality
(2) Local exhaust fans in each kitchen and bathroom to reduce the levels of contaminants and moisture in these spaces
We'll focus on spot ventilation here. Read more about whole-house ventilation here.
The ASHRAE standard covers spot ventilation requirements for bathrooms and other areas. For bathrooms, the fan must deliver a minimum of 50 cubic feet per minute (CFM) of exhaust ventilation. For kitchen ventilation, the standard is 100 CFM.
ASHRAE provides a number of options to determine proper operation. The first is using the rated performance of the fan at .25 static pressure (Ps) tested per the standards of the Home Ventilating Institute (HVI).
Alternatively, the fan or range hood can be tested after installation using test equipment such as a “flow hood.” Some building codes and green building standards require the use of this method. Additionally as with whole house mechanical ventilation, there are sound requirements for local exhaust fans in the kitchen and bathroom. These fans must have a sound level no greater than 3 Sones so that the fans aren't too loud for people to use them.
Because today's homes are built with less air infiltration, there’s less natural ventilation in the home. That can be a problem for kitchen ventilation fans such as range hoods.
The answer is make-up air.
Make-up air is introduced directly into the home through intelligent make-up air systems that are generally incorporated into the home’s kitchen and bathroom ventilation systems, The interlocked damper, like BROAN’s Automatic Interlocked Make-up Air Damper for kitchen ventilation fans and range hoods, was the first code-compliant make-up air system.
The damper automatically opens to let fresh, outdoor air into the home when a ventilation fan or range hood is turned on. When the system is turned off, the damper tightly closes to prevent unwanted air from entering the home, helping the homeowner conserve energy during heating and cooling cycles.
With a properly designed and installed interlocked make-up air damper, homeowners have the assurance that when the fan or range hood is on, the air intake and exhaust are equalized, establishing the ideal balance of air pressure levels for proper ventilation and superior indoor air quality. The interlocked damper is unique in that it only operates when necessary, which allows homeowners to control their energy costs and prevent extraneous and expensive energy usage.
To help building professionals decipher make-up air regulations and identify appropriate solutions, Broan-NuTone conducted an online educational webinar, “Residential Kitchen Make-Up Air: Designing and Specifying Code Compliant Systems,” and developed the “Range Hood Make-Up Air Specifier” tool, both of which can be found on the BROAN.com andBESTrangehoods.com websites.