Current through Register Vol. 48, No. 39, March 25, 2024
Subpart
1.
Section R403.2.1.
IECC section R403.2.1, Insulation (prescriptive), is deleted in
its entirety and replaced with the following:
R403.2.1
Insulation
(prescriptive). All outdoor air intakes, exhaust, supply, and return air
ducts and plenums shall be insulated according to Table R403.2.1.
For the purposes of Table R403.2.1, the following
applies:
a. Insulation is only
required in the conditioned space for a distance of 3 feet (914 mm) from the
exterior or unconditioned space.
b.
V means the vapor retarder required in accordance with IMC section
604.11.
When a vapor retarder is required, duct insulation required by this section
shall be installed without respect to other building envelope
insulation.
c. W means an approved
weatherproof barrier.
TABLE R403.2.1 MINIMUM REQUIRED DUCT AND PLENUM
INSULATION FOR DWELLING UNITS
Duct Type/Location
|
Requirements
|
Exterior of building |
R-8, V, and W |
Attics, garages, and ventilated crawl spaces |
R-8 and V |
Outdoor air intakes within conditioned spaces |
R-3.3 and V |
Exhaust ducts within conditioned spaces |
R-3.3 and V |
Within concrete slab or within ground |
R-3.5 and V |
Within conditioned spaces and in basements with insulated
walls |
None required |
Subp. 2.
Section R403.5.
IECC section R403.5 and its subsections are deleted except for
Table R403.5.1 and replaced with the following:
R403.5
Mechanical ventilation
(mandatory). The building shall be provided with a balanced mechanical
ventilation system that is +/- 10 percent of the systems design capacity and
meets the requirements of section R403.5.5, which establishes the continuous
and total mechanical ventilation requirements for dwelling unit ventilation.
All conditioned unfinished basements, conditioned crawl spaces, and conditioned
levels shall be provided with a minimum ventilation rate of 0.02 cfm per square
foot or a minimum of 1 supply duct and 1 return duct. The supply and return
ducts shall be separated by 1/2 the diagonal dimension of the basement to avoid
a short circuit of the air circulation. Outdoor air intakes and exhausts shall
have automatic or gravity dampers that close when the ventilation system is not
operating.
Exception: Kitchen and bath fans that are not
included as part of the mechanical ventilation system are exempt from these
requirements.
R403.5.1
Alterations. Alterations to existing buildings are exempt from
meeting the requirements of section R403.5.
R403.5.2
Total ventilation rate.
The mechanical ventilation system shall provide sufficient outdoor air to equal
the total ventilation rate average for each 1-hour period in accordance with
Table R403.5.2, or equation R403.5.2, based on the number of bedrooms and
square footage of conditioned space, including the basement and conditioned
crawl spaces.
For the purposes of Table R403.5.2 and section R403.5.3, the
following applies:
a. Equation
R403.5.2 Total ventilation rate: Total ventilation rate (cfm) = (0.02 x square
feet of conditioned space) + (15 x (number of bedrooms + 1))
b. Equation R403.5.2.1 Continuous ventilation
rate: Continuous ventilation rate (cfm) = Total ventilation rate/2
Table R403.5.2
|
Number of Bedrooms |
|
1 |
2 |
3 |
4 |
5 | 6² |
Conditioned
space¹ (in sq. ft.) |
Total/Continuous |
Total/Continuous |
Total/Continuous |
Total/Continuous |
Total/Continuous |
Total/Continuous |
1000-1500 |
60/40 |
75/40 |
90/45 |
105/53 |
120/60 |
135/68 |
1501-2000 |
70/40 |
85/43 |
100/50 |
115/58 |
130/65 |
145/73 |
2001-2500 |
80/40 |
95/48 |
110/55 |
125/63 |
140/70 |
155/78 |
2501-3000 |
90/45 |
105/53 |
120/60 |
135/68 |
150/75 |
165/83 |
3001-3500 |
100/50 |
115/58 |
130/65 |
145/73 |
160/80 |
175/88 |
3501-4000 |
110/55 |
125/63 |
140/70 |
155/78 |
170/85 |
185/93 |
4001-4500 |
120/60 |
135/68 |
150/75 |
165/83 |
180/90 |
195/98 |
4501-5000 |
130/65 |
145/73 |
160/80 |
175/88 |
190/95 |
205/103 |
5001-5500 |
140/70 |
155/78 |
170/85 |
185/93 |
200/100 |
215/108 |
5501-6000² |
150/75 |
165/83 |
180/90 |
195/98 |
210/105 |
225/113 |
1. Conditioned
space includes the basement and conditioned crawl spaces.
2. If conditioned space exceeds 6000 sq. ft.
or there are more than 6 bedrooms, use equation R403.5.2.
R403.5.3
Continuous
ventilation rate. Continuous ventilation rate (CVR) is a minimum of 50
percent of the total ventilation rate (TVR). The CVR shall not be less than 40
cfm and shall provide a continuous average cfm rate according to Table R403.5.2
or according to equation R403.5.2 for every 1-hour period. The portion of the
ventilation system that is intended to be continuous may have automatic cycling
controls to provide the average flow rate for each hour.
R403.5.4
Intermittent ventilation
rate. Intermittent ventilation rate means the difference between the
total ventilation rate and the continuous ventilation rate.
R403.5.5
Balanced and HRV/ERV
systems. All balanced systems shall be balanced so that the air intake
is within 10 percent of the exhaust output.
A heat recovery ventilator (HRV) or energy recovery ventilator
(ERV) shall meet either:
1. the
requirements of HVI Standard 920, 72 hours minus 13°F (-10°C) cold
weather test; or
2. certified by a
registered professional engineer and installed per manufacturers installation
instructions.
An HRV or ERV intended to comply with both the continuous and
total ventilation rate requirements shall meet the rated design capacity of the
continuous ventilation rate specified in section R403.5.3 under low capacity
and meet the total ventilation rate specified in section R403.5.2 under high
capacity.
Exception: The balanced system and HRV/ERV system
may include exhaust fans to meet the intermittent ventilation rate. Surface
mounted fans shall have a maximum 1.0 sone per HVI Standard
915.
R403.5.6
Installation requirements. All mechanical systems shall meet the
requirements of section R403.5.6. The mechanical ventilation system and its
components shall also be installed according to the Minnesota Mechanical Code,
Minnesota Rules, chapter 1346, and the equipment manufacturers installation
instructions.
R403.5.6.1
Air
distribution/circulation. Outdoor air shall be delivered to each
habitable space by a forced air circulation system, separate duct system, or
individual inlets.
R403.5.6.1.1
Forced
air circulation systems. When outdoor air is supplied directly through a
forced air circulation system, the requirements of this section shall be met
using one of the following methods:
a. when
an outdoor air supply is not ducted to the forced air system, controls shall be
installed to allow the forced air system to provide an average circulation flow
rate each hour of not less than 0.15 cfm per square foot of the conditioned
floor area; or
b. when the outdoor
air supply is ducted to the forced air system, the mixed air temperature shall
not be less than the heating equipment manufacturers installation instructions.
The controls shall be installed to allow the forced air circulation system to
provide an average flow rate not less than 0.075 cfm per square foot of
conditioned floor area.
R403.5.6.1.2
Directly ducted and
individual room inlets. When outdoor air is supplied directly to
habitable spaces with an airflow of 20 cfm or greater, the system shall be
designed and installed to temper incoming air to not less than 40°F
(4°C) measured at the point of distribution into the space.
R403.5.6.1.3
Airflow
verification. All mechanical ventilation system airflows greater than 30
cfm at the building exhaust or intake shall be tested and verified. The airflow
verification results shall be made available to the building official upon
request.
R403.5.7
Fans. When used as part
of the mechanical ventilation system, fans shall be capable of delivering the
designed air flow at the point of air discharge or intake as determined by
section R403.5.2 and according to HVI Standard 916. Fans shall be designed and
certified by the equipment manufacturer to be capable of continuous operation
at the maximum fan-rated cfm. Surface mounted fans used to comply with the
continuous ventilation requirement of the mechanical ventilation system shall
have a maximum 1.0 sone, according to HVI Standard 915. Fans used to comply
with the intermittent ventilation requirement of the mechanical ventilation
system shall have a maximum 2.5 sone, according to HVI Standard 915. Mechanical
ventilation system fans shall meet the efficacy requirements of Table R403.5.1.
Exception to sone requirements: Sone requirements
do not apply to forced air circulation systems and remotely mounted fans. If
the remotely mounted fan is not in a habitable space and there are at least 4
feet of ductwork between the fan and grille, then the fan sone rating shall be
2.5 sone or less. Where mechanical ventilation fans are integral to tested and
listed HVAC equipment, the fans shall be powered by an electronically
commutated motor.
R403.5.8
Multifan systems. When two or more fans in a dwelling unit share a
common duct, each fan shall be equipped with a backdraft damper to prevent
recirculation of exhaust air into another room.
R403.5.9
Connection to forced air
circulation systems. When air ducts are directly connected to the forced
air circulation system, the outdoor air shall be supplied directly to the
forced air circulation system, or the exhaust air shall be drawn directly from
the forced air circulation system, but not both. To meet the mechanical
ventilation system requirements, the air duct shall be installed according to
the manufacturers installation instructions.
Exception: Both outdoor air and exhaust air may be
connected to the forced air circulation system only if controls are installed
to operate the forced air circulation system when the mechanical ventilation
system is operating or other means are provided to prevent short circuiting of
ventilation air in accordance with the manufacturers
recommendations.
R403.5.10
Dampers. The
mechanical ventilation system supply and exhaust ducts shall be provided with
accessible backflow dampers to minimize flow to or from the outdoors when the
ventilation system is off.
R403.5.11
Intake openings.
Exterior air intake openings shall be accessible for inspection and
maintenance. Intake openings shall be located according to the Minnesota
Mechanical Code, Minnesota Rules, chapter 1346, and shall be covered with a
corrosion-resistant screen of not less than 1/4-inch (6.4 mm) mesh. Intake
openings shall be located at least 12 inches (305 mm) above adjoining grade
level.
Exception: Combination air intake and exhaust
hoods may be approved by the building official when specifically allowed by the
equipment manufacturers installation instructions.
R403.5.12
Filtration. All
mechanically supplied outdoor air shall have a filter with a designated minimum
efficiency of MERV 4 as defined by ASHRAE Standard 52.2. The filter location
shall be prior to the air entering the thermal conditioning components, blower,
or habitable space. The filter shall be installed so it is readily accessible
and facilitates regular service.
R403.5.13
Noise and vibration.
Mechanical ventilation system components shall be installed to minimize
transmission of noise and vibration. The equipment manufacturers installation
instructions shall be followed and any materials provided by the equipment
manufacturer for installation shall be used. In the absence of specific
materials or instructions, vibration dampening materials, such as rubber
grommets and flexible straps, shall be used when connecting fans and heat
exchangers to the building structure. Isolation duct connectors shall be used
to mitigate noise transmission.
R403.5.14
Controls. Balanced
mechanical ventilation system controls shall comply with all the following:
1. When the mechanical ventilation system is
not designed to operate whenever the forced air circulation system is
operating, the mechanical ventilation system shall incorporate an accessible
backflow damper to prevent flow from the outside when the mechanical
ventilation system is off.
2.
Controls shall be compatible with the mechanical ventilation system, its
components, and the manufacturers installation and operating
instructions.
3. Controls shall be
installed to operate the mechanical ventilation system as designed.
4. Each control shall be readily accessible
to occupants and shall be labeled to indicate the controls function.
R403.5.15
Labeling.
All ventilation intake and exhaust outlets shall include permanent,
weather-resistant identification labels on the buildings exterior.
R403.5.16
Documentation.
Documentation, which includes proper operation and maintenance instructions,
shall accompany all mechanical ventilation systems. The documentation shall be
in a conspicuous and readily accessible location.
R403.5.17
Climatic design
conditions.
A. HVAC equipment shall be
sized according to the ACCA Manual S or an equivalent method, based on the
buildings heating and cooling load calculations by using ASHRAE Handbook of
Fundamentals or the ACCA Manual J. Oversizing of heating equipment shall not
exceed 40 percent of the calculated load requirements and oversizing of cooling
equipment shall not exceed 15 percent of the calculated load
requirements.
B. Design conditions
shall be determined according to Table 403.5.17. Design condition adjustments
may be determined by the building official if local climates differ from the
tabulated temperatures based on local climate data.
TABLE R403.5.17 Climatic Data Design
Conditions
|
City
|
Summer Db/Wb °F
|
Winter Db °F
|
Aitkin |
82/72 |
-24 |
Albert Lea |
85/72 |
-15 |
Alexandria |
86/70 |
-21 |
Bemidji |
84/68 |
-24 |
Cloquet |
82/68 |
-20 |
Crookston |
84/70 |
-27 |
Duluth |
81/67 |
-20 |
Ely |
82/68 |
-29 |
Eveleth |
82/68 |
-26 |
Faribault |
86/73 |
-16 |
Fergus Falls |
86/71 |
-21 |
Grand Rapids |
81/67 |
-23 |
Hibbing |
82/68 |
-19 |
International Falls |
83/67 |
-28 |
Litchfield |
85/71 |
-18 |
Little Falls |
86/71 |
-20 |
Mankato |
86/72 |
-15 |
Minneapolis/St. Paul |
88/72 |
-15 |
Montevideo |
86/72 |
-17 |
Mora |
84/70 |
-21 |
Morris |
84/72 |
-21 |
New Ulm |
87/73 |
-15 |
Owatonna |
86/73 |
-16 |
Pequot Lakes |
84/68 |
-23 |
Pipestone |
85/73 |
-15 |
Redwood Falls |
89/73 |
-17 |
Rochester |
85/72 |
-17 |
Roseau |
82/70 |
-29 |
St. Cloud |
86/NA |
-20 |
Thief River Falls |
82/68 |
-25 |
Tofte |
75/61 |
-14 |
Warroad |
83/67 |
-29 |
Wheaton |
84/71 |
-20 |
Willmar |
85/71 |
-20 |
Winona |
88/74 |
-13 |
Worthington |
84/71 |
-14 |
Db = dry bulb temperature, degrees
Fahrenheit |
Wb = wet bulb temperature, degrees
Fahrenheit |
Subp. 3.
Section R403.12.
IECC section R403 is amended by adding section R403.12 as
follows:
R403.12
Photovoltaic
modules and systems: Installation of photovoltaic modules and systems
shall meet the requirements of Minnesota Rules, chapter 1315.