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Minnesota Administrative Rules

1346.0501 SECTION 501 GENERAL.

Subpart 1.

Section 501.2.

IMC Section 501.2 is amended to read as follows:

501.2 Exhaust discharge. The air removed by every mechanical exhaust system shall be discharged outdoors at a point where it will not cause a nuisance and not less than the distances specified in Section 501.2.1. The air shall be discharged to a location from which it cannot again be readily drawn in by a ventilating system. Air shall not be exhausted into an attic or crawl space and the exhaust system shall be equipped with a backdraft damper at the point of discharge.

Exception:

1. Commercial cooking recirculating systems.

Subp. 2.

Section 501.3.

IMC Section 501.3 is amended to read as follows:

501.3 Pressure equalization. Mechanical exhaust systems shall be sized and operated to remove the quantity of air required by this chapter. If a greater quantity of air is supplied by a mechanical ventilating supply system than is removed by a mechanical exhaust system for a room, adequate means shall be provided for the natural exit of the excess air supplied.

501.3.1 Makeup air in new dwellings. Makeup air quantity for new dwellings shall be determined by using Table 501.3.1 and shall be supplied in accordance with IMC Section 501.3.2.

Exception. Makeup air provisions of IMC Section 501.3.1 are not required when any of the following are demonstrated:

1. A test is performed according to ASTM Standard E1998-02 ( 2007), Standard Guide for Assessing Depressurization-Induced Backdrafting and Spillage from Vented Combustion Appliances, and documentation is provided that the vented combustion appliances continue to operate within established parameters of the test.

2. A test approved by the building official verifies proper operation of vented combustion appliances.

501.3.2 Makeup air supply. Makeup air shall be provided by one of the following methods:

1. Passive makeup air shall be provided by passive openings according to the following:

1.1 Passive makeup air openings from the outdoors shall be sized according to Table 501.3.2.

1.2 Barometric dampers are prohibited in passive makeup air openings when any atmospherically vented appliance is installed.

1.3 Single passive openings larger than 8 inches (204 mm) diameter, or equivalent, shall be provided with a motorized damper that is electrically interlocked with the largest exhaust system.

2. Powered makeup air shall be provided if the size of a single opening or multiple openings exceeds 11 inches (280 mm) diameter, or equivalent, when sized according to Table 501.3.2. Powered makeup air shall comply with the following:

2.1 Powered makeup air shall be electrically interlocked with the largest exhaust system.

2.2 Powered makeup air shall be matched to the airflow of the largest exhaust system.

3. Makeup air shall be provided by a combination of passive openings and powered means according to Table 501.3.2 and the following:

3.1 Passive makeup air openings shall comply with Item 1.

3.2 Powered makeup air shall be supplied for the quantity of airflow in excess of the passive makeup air opening provided, and it shall be electrically interlocked with the exhaust system.

501.3.2.1 Makeup air ducts. Makeup air ducts shall be constructed and installed according to IMC Chapter 6 and Section 501.3.2.

501.3.2.2 Makeup air intake. Makeup air intake openings shall be located to avoid intake of exhaust air in accordance with IMC Section 401.5.2 and IFGC Section 503.8, and shall be covered with corrosion resistant screen of not less than 1/4 inch (6.4 mm) mesh. Makeup air intake openings shall be located at least 12 inches (305 mm) above adjoining grade level.

501.3.2.3 Makeup air location. Makeup air requirements of 175 cubic feet per minute (cfm) (0.084 m3/s) and greater shall be introduced to the dwelling in one of the following locations:

1. In the space containing the vented combustion appliances.

2. In the space containing the exhaust system.

3. In a space that is freely communicating with the exhaust system and is approved by the building official.

501.3.2.4 Makeup air termination restriction. A makeup air opening shall not terminate in the return air plenum of a forced air heating system unless it is installed according to the heating equipment manufacturer's installation instructions.

501.3.2.5 Separate makeup air and combustion air openings. When both makeup air and combustion air openings are required, they shall be provided through separate openings to the outdoors. Refer to IFGC Section 304, to determine requirements for air for combustion and ventilation.

Exception: Combination makeup air and combustion air systems may be approved by the building official where they are reasonably equivalent in terms of health, safety, and durability.

501.3.2.6 Makeup air effectiveness. The makeup air shall not reduce the effectiveness of exhaust systems or performance of vented combustion appliances, and makeup air shall not adversely affect the heating or cooling capability of the mechanical equipment.

501.3.3 Additions, alterations, or installations of mechanical systems in existing dwellings. Makeup air shall be supplied to existing dwellings when any of the following conditions occur:

1. If a dwelling was constructed after 2003 using the makeup air provisions of IMC Section 501.3.2, makeup air quantity shall be determined by using Table 501.3.1 and shall be supplied according to IMC Section 501.3.2 when any of the following conditions occur:

1.1 A vented combustion appliance, including a solid fuel appliance, is installed or replaced.

1.2 An exhaust system is installed or replaced.

Exception: If powered makeup air is electrically interlocked and matched to the airflow of the exhaust system, additional makeup air is not required.

2. If a dwelling was constructed after 1999 using the provisions of the Minnesota Energy Code, Minnesota Rules, chapter 7672, makeup air quantity shall be determined by using IMC Table 501.3.1 and shall be supplied in accordance with IMC Section 501.3.2 when any of the following conditions occur:

2.1 A vented combustion appliance, including a solid fuel appliance, is installed or replaced.

2.2 An exhaust system is installed or replaced.

Exception: If powered makeup air is electrically interlocked and matched to the airflow of the exhaust system, additional makeup air is not required.

3. When a solid fuel appliance is installed in a dwelling constructed during or after 1994 under the Minnesota Energy Code, Minnesota Rules, chapter 7670, makeup air quantity shall be determined by using IMC Table 501.3.1 and shall be supplied according to IMC Section 501.3.2.

Exception. If a closed combustion solid fuel burning appliance is installed with combustion air in accordance with the manufacturer's installation instructions, additional makeup air is not required.

4. When an exhaust system with a rated capacity greater than 300 cfm (0.144 m3/s) is installed in a dwelling constructed during or after 1994 under the Minnesota Energy Code, Minnesota Rules, chapter 7670, makeup air quantity shall be determined by using IMC Table 501.3.3(1) and shall be supplied according to IMC Section 501.3.2.

Exception: If powered makeup air is electrically interlocked and matched to the airflow of the exhaust system additional makeup air is not required.

5. When an exhaust system with a rated capacity greater than 300 cfm (0.144 m3/s) is installed in a dwelling constructed prior to 1994, makeup air quantity shall be determined by using IMC Table 501.3.3(2) and shall be supplied according to IMC Section 501.3.2.

Exception: If powered makeup air is electrically interlocked and matched to the airflow of the exhaust system, additional makeup air is not required.

6. When a solid fuel appliance is installed in a dwelling constructed prior to 1994, makeup air quantity shall be determined by using IMC Table 501.3.3(3) and shall be supplied according to IMC Section 501.3.2.

Exception: If a closed combustion solid fuel burning appliance is installed with combustion air in accordance with the manufacturer's installation instructions, additional makeup air is not required.

Exception: Makeup air is not required in Items 1 to 6 when any of the following are demonstrated:

1. A test is performed according to ASTM Standard E1998-02 ( 2007), Standard Guide for Assessing Depressurization-Induced Backdrafting and Spillage from Vented Combustion Appliances, and documentation is provided that the vented combustion appliances continue to operate within established parameters of the test.

2. A test approved by the building official verifies proper operation of vented combustion appliances.

Table 501.3.1

Procedure to Determine Makeup Air Quantity for Exhaust Equipment in Dwellings

One or multiple power vent or direct vent appliances or no combustion appliancesA One or multiple fan-assisted appliances and power vent or direct vent appliancesB One atmospherically vented gas or oil appliance or one solid fuel applianceC Multiple atmospherically vented gas or oil appliances or solid fuel appliancesD
1. Use the Appropriate Column to Estimate House Infiltration
a) pressure factor (cfm/sf) 0.15 0.09 0.06 0.03
b) conditioned floor area (sf)
(including unfinished basements)
Estimated House Infiltration (cfm): [1a x 1b]
2. Exhaust Capacity
a) continuous exhaust-only ventilation system (cfm):
(not applicable to balanced ventilation systems such as HRV)
b) clothes dryer 135 135 135 135
c) 80% of largest exhaust rating (cfm):
(not applicable if recirculating system or if powered makeup air is electrically interlocked and matched to exhaust)
d) 80% of next largest exhaust rating (cfm): not applicable
(not applicable if recirculating system or if powered makeup air is electrically interlocked and matched to exhaust)
Total Exhaust Capacity (cfm): [2a+2b+2c+2d]
3. Makeup Air Requirement
a) Total Exhaust Capacity (from above)
b) Estimated House Infiltration (from above)
Makeup Air Quantity (cfm): [3a - 3b]
(if value is negative, no makeup air is needed)

4. For Makeup Air Opening Sizing, refer to Table 501.3.2

AUse this column if there are other than fan-assisted or atmospherically vented gas or oil appliances or if there are no combustion appliances.

BUse this column if there is one fan-assisted appliance per venting system. Other than atmospherically vented appliances may also be included.

CUse this column if there is one atmospherically vented (other than fan-assisted) gas or oil appliance per venting system or one solid fuel appliance.

DUse this column if there are multiple atmospherically vented gas or oil appliances using a common vent or if there are atmospherically vented gas or oil appliances and solid fuel appliances.

Table 501.3.2

Makeup Air Opening Sizing Table for New and Existing Dwellings

One or multiple power vent or direct vent appliances or no combustion appliancesA One or multiple fan-assisted appliances and power vent or direct vent appliancesB One atmospher-
ically vented gas or oil appliance or one solid fuel applianceC
Multiple atmospher-
ically vented gas or oil appliances or solid fuel appliancesD
Passive makeup air opening duct diameterE,F,G
Type of opening or system (cfm) (cfm) (cfm) (cfm) (inches)
Passive Opening 1-36 1-22 1-15 1-9 3
Passive Opening 37-66 23-41 16-28 10-17 4
Passive Opening 67-109 42-66 29-46 18-28 5
Passive Opening 110-163 67-100 47-69 29-42 6
Passive Opening 164-232 101-143 70-99 43-61 7
Passive Opening 233-317 144-195 100-135 62-83 8
Passive Opening with Motorized Damper 318-419 196-258 136-179 84-110 9
Passive Opening with Motorized Damper 420-539 259-332 180-230 111-142 10
Passive Opening with Motorized Damper 540-679 333-419 231-290 143-179 11
Powered Makeup AirH >679 >419 >290 >179 Not Applicable

AUse this column if there are other than fan-assisted or atmospherically vented gas or oil appliances or if there are no combustion appliances.

BUse this column if there is one fan-assisted appliance per venting system. Other than atmospherically vented appliances may also be included.

CUse this column if there is one atmospherically vented (other than fan-assisted) gas or oil appliance per venting system or one solid fuel appliance.

DUse this column if there are multiple atmospherically vented gas or oil appliances using a common vent or if there are atmospherically vented gas or oil appliances and solid fuel appliance(s).

EAn equivalent length of 100 feet of round smooth metal duct is assumed. Subtract 40 feet for the exterior hood and ten feet for each 90-degree elbow to determine the remaining length of straight duct allowable.

FIf flexible duct is used, increase the duct diameter by one inch. Flexible duct shall be stretched with minimal sags.

GBarometric dampers are prohibited in passive makeup air openings when any atmospherically vented appliance is installed.

HPowered makeup air shall be electrically interlocked with the largest exhaust system.

Table 501.3.3(1)

Procedure to Determine Makeup Air Quantity for Exhaust Equipment in Existing Dwellings

(Refer to Item 4 in Section 501.3.3 to determine applicability of this table)

One or multiple power vent or direct vent appliances or no combustion appliancesA One or multiple fan-assisted appliances and power vent or direct vent appliancesB One atmospherically vented gas or oil appliance or one solid fuel applianceC Multiple atmospherically vented gas or oil appliances or solid fuel appliancesD
1. Use the Appropriate Column to Estimate House Infiltration
a) pressure factor (cfm/sf) 0.15 0.09 0.06 0.03
b) conditioned floor area (sf)
Estimated House Infiltration (cfm): [1a x 1b]
2. Exhaust Capacity
80% of exhaust rating = Exhaust Capacity (cfm):
(not applicable if recirculating system or if powered makeup air is electrically interlocked and matched to exhaust)
3. Makeup Air Requirement
a) Exhaust Capacity (from above)
b) Estimated House Infiltration (from above)
Makeup Air Quantity (cfm): [3a - 3b]
(if value is negative, no makeup air is needed)

4. For Makeup Air Opening Sizing, refer to Table 501.3.2

AUse this column if there are other than fan-assisted or atmospherically vented gas or oil appliances or if there are no combustion appliances.

BUse this column if there is one fan-assisted appliance per venting system. Other than atmospherically vented appliances may also be included.

CUse this column if there is one atmospherically vented (other than fan-assisted) gas or oil appliance per venting system or one solid fuel appliance.

DUse this column if there are multiple atmospherically vented gas or oil appliances using a common vent or if there are atmospherically vented gas or oil appliances and solid fuel appliances.

Table 501.3.3(2)

Procedure to Determine Makeup Air Quantity for Exhaust Equipment in Existing Dwellings

(Refer to Item 5 in Section 501.3.3 to determine applicability of this table)

One or multiple power vent or direct vent appliances or no combustion appliancesA One or multiple fan-assisted appliances and power vent or direct vent appliancesB One atmospherically vented gas or oil appliance or one solid fuel applianceC Multiple atmospherically vented gas or oil appliances or solid fuel appliancesD
1. Use the Appropriate Column to Estimate House Infiltration
a) pressure factor (cfm/sf) 0.25 0.15 0.10 0.05
b) conditioned floor area (sf)
(including unfinished basements)
Estimated House Infiltration (cfm): [1a x 1b]
or
Alternative Calculation (by using blower door test)E
c) conversion factor 0.75 0.45 0.30 0.15
d) CFM50 value (from blower door test)
Estimated House Infiltration (cfm): [1c x 1d]
2. Exhaust Capacity
80% of exhaust rating = Exhaust Capacity (cfm):
(not applicable if recirculating system or if powered makeup air is electrically interlocked with exhaust)
3. Makeup Air Requirement
a) Exhaust Capacity (from above)
b) Estimated House Infiltration (from above)
Makeup Air Quantity (cfm): [3a - 3b]
(if value is negative, no makeup air is needed)

4. For Makeup Air Opening Sizing, refer to Table 501.3.2

AUse this column if there are other than fan-assisted or atmospherically vented gas or oil appliances or if there are no combustion appliances.

BUse this column if there is one fan-assisted appliance per venting system. Other than atmospherically vented appliances may also be included.

CUse this column if there is one atmospherically vented (other than fan-assisted) gas or oil appliance per venting system or one solid fuel appliance.

DUse this column if there are multiple atmospherically vented gas or oil appliances using a common vent or if there are atmospherically vented gas or oil appliances and solid fuel appliances.

EAs an alternative, the Estimated House Infiltration may be calculated by performing a blower door test and multiplying the conversion factor by the CFM50 value.

Table 501.3.3(3)

Procedure to Determine Makeup Air Quantity for Exhaust Equipment in Existing Dwellings

(Refer to Item 6 in Section 501.3.3 to determine applicability of this table)

One or multiple power vent or direct vent appliances or no combustion appliancesA One or multiple fan-assisted appliances and power vent or direct vent appliancesB One atmospherically vented gas or oil appliance or one solid fuel applianceC Multiple atmospherically vented gas or oil appliances or solid fuel appliancesD
1. Use the Appropriate Column to Estimate House Infiltration
a) pressure factor (cfm/sf) 0.25 0.15 0.10 0.05
b) conditioned floor area (sf)
(including unfinished basements)
Estimated House Infiltration (cfm): [1a x 1b]
or
Alternative Calculation (by using blower door test)E
c) conversion factor 0.75 0.45 0.30 0.15
d) CFM50 value (from blower door test)
Estimated House Infiltration (cfm): [1c x 1d]
2. Exhaust Capacity
a) continuous exhaust-only ventilation system (cfm)
(not applicable to balanced ventilation systems)
b) clothes dryer (cfm) 135 135 135 135
c) 80% of largest exhaust rating (cfm):
(not applicable if recirculating system or if powered makeup air is electrically interlocked and with exhaust)
d) 80% of next largest exhaust rating (cfm) Not applicable
(not applicable if recirculating system or if powered makeup air is electrically interlocked with exhaust)
Total Exhaust Capacity (cfm): [2a+2b+2c+2d]
3. Makeup Air Requirement
a) Total Exhaust Capacity (from above)
b) Estimated House Infiltration (from above)
Makeup Air Quantity (cfm): [3a - 3b]
(if value is negative, no makeup air is needed)

4. For Makeup Air Opening Sizing, refer to Table 501.3.2

AUse this column if there are other than fan-assisted or atmospherically vented gas or oil appliances or if there are no combustion appliances.

BUse this column if there is one fan-assisted appliance per venting system. Other than atmospherically vented appliances may also be included.

CUse this column if there is one atmospherically vented (other than fan-assisted) gas or oil appliance per venting system or one solid fuel appliance.

DUse this column if there are multiple atmospherically vented gas or oil appliances using a common vent or if there are atmospherically vented gas or oil appliances and solid fuel appliances.

EAs an alternative, the Estimated House Infiltration may be calculated by performing a blower door test and multiplying the conversion factor by the CFM50 value.

Statutory Authority:

MS s 16B.59; 16B.61; 16B.64; 326B.101; 326B.106; 326B.13

History:

29 SR 299; L 2007 c 140 art 1 s 1; 34 SR 537

Published Electronically:

October 23, 2009

700 State Office Building, 100 Rev. Dr. Martin Luther King Jr. Blvd., St. Paul, MN 55155 ♦ Phone: (651) 296-2868 ♦ TTY: 1-800-627-3529 ♦ Fax: (651) 296-0569