Subsection R403.6 - Mechanical ventilationR403.6 Revise the section as follows:
Outdoor air intakes and exhausts shall have automatic or gravity dampers that close when the ventilation system is not operating.
Each dwelling unit of a residential building shall be provided with continuously operating exhaust, supply or balanced mechanical ventilation that has been site verified to meet a minimum airflow per one of the following methods:
1. Table R403.6.1 TABLE R403.6.1 MINIMUM REQUIRED AIRFLOW IN CFM BASED ON SIZE OF HOUSE AND NUMBER OF BEDROOMS
Size of House | 0-1 bedrooms | 2-3 bedrooms | 4-5 bedrooms | 6-7 bedrooms | >7 bedrooms |
Up to 1500 sq ft | 30 | 45 | 60 | 75 | 90 |
1501 - 3000 sq ft | 45 | 60 | 75 | 90 | 105 |
3001 - 4500 sq ft | 60 | 75 | 90 | 105 | 120 |
4501 - 6000 sq ft | 75 | 90 | 105 | 120 | 135 |
6001 - 7500 sq ft | 90 | 105 | 120 | 135 | 150 |
> 7500 sq ft | 105 | 120 | 135 | 150 | 165 |
4. the following formula for one- and two-family dwellings and townhouses of three or less stories above grade plane: Click to view image
Where: CFA is the conditioned floor area in sq ft
Nbr is the number of bedrooms
Q50 is the verified blower door air leakage rate in cfm measured at 50 Pascals
S is the building height factor determined by this table:
stories above grade plane | 1 | 2 | 3 |
S | 1.00 | 1.32 | 1.55 |
WSF is the shielded weather factor as determined by this table:
County | WSF |
Barnstable | 0.60 |
Berkshire | 0.52 |
Bristol | 0.54 |
Dukes | 0.59 |
Essex | 0.58 |
Franklin | 0.52 |
Hampden | 0.49 |
Hampshire | 0.59 |
Middlesex | 0.55 |
Nantucket | 0.61 |
Norfolk | 0.52 |
Plymouth | 0.53 |
Suffolk | 0.66 |
Worcester | 0.59 |
Revise and Replace R403.6.3 and add sections R403.6.4 through R403.6.7 as follows:
R403.6.3Testing and Verification. Installed performance of the mechanical ventilation system shall be tested and verified by a HERS Rater, HERS Rating Field Inspector, or an applicable BPI Certified Professional, and measured using a flow hood, flow grid, or other airflow measuring device in accordance with either RESNET Standard Chapter 8 or ACCA Standard 5.R403.6.4Air-moving equipment, selection and installation. As referenced in ASHRAE Standard 62.2-2013, Section 7.1, ventilation devices and equipment shall be tested and certified by AMCA (Air Movement and Control Association) or HVI (Home Ventilating Institute) and the certification label shall be found on the product. Installation of systems or equipment shall be carried out in accordance with manufacturers' design requirements and installation instructions. Where multiple duct sizes and/or exterior hoods are standard options, the minimum size shall not be used.R403.6.5Sound Rating. Sound ratings for fans used for whole building ventilation shall be rated at a maximum of 1.0 sone. Exception: HVAC air handlers and remote-mounted fans need not meet sound requirements. There must be at least 4ft of ductwork between the remote-mounted fan and intake grille.
R403.6.6Documentation. The owner and the occupant of the dwelling unit shall be provided with information on the ventilation design and systems installed, as well as instructions on the proper operation and maintenance of the ventilation systems. Ventilation controls shall be labeled with regard to their function, unless the function is obvious.R403.6.7Air Inlets and Exhausts. All ventilation air inlets shall be located a minimum of 10ft from vent openings for plumbing drainage systems, appliance vent outlets, exhaust hood outlets, vehicle exhaust, or other known contamination sources; and shall not be obstructed by snow, plantings, or any other material. Outdoor forced air inlets shall be covered with rodent screens having mesh openings not greater than 1/2 inch. A whole house mechanical ventilation system shall not extract air from an unconditioned basement unless approved by a registered design professional. Where wall inlet or exhaust vents are less than seven feet above finished grade in the area of the venting, including but not limited to decks and porches, a metal or plastic identification plate shall be permanently mounted to the exterior of the building at a minimum height of eight feet above grade directly in line with the vent terminal. The sign shall read, in print size no less than 1/2 inch in size, "MECH. VENT DIRECTLY BELOW. KEEP CLEAR OF ALL OBSTRUCTIONS". Exceptions:
1. Ventilation air inlets in the wall $ 3 ft. from dryer exhausts and contamination sources exiting through the roof.2. No minimum separation distance shall be required between local exhaust outlets in kitchens/bathrooms and windows.3. Vent terminations that meet the requirements of the National Fuel Gas Code (NFPA 54/ ANSI Z223.1) or equivalent.780 CMR, ch. 51, ch. 4, R401, R403.6
Amended by Mass Register Issue 1532, eff. 10/11/2024.