Minn. R. agency 151, ch. 1346, MINNESOTA MECHANICAL CODE, pt. 1346.0501

Current through Register Vol. 49, No. 20, November 12, 2024

Part 1346.0501 - SECTION 501 GENERAL

Subpart 1.Section 5012.

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 501.4.

IMC section 501.4 is amended and subsections added to read as follows:

501.4Pressure 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.

501.4.1Makeup air in new dwellings. Makeup air quantity for new dwellings shall be determined by using Table 501.4.1 and shall be supplied in accordance with section 501.4.2.

501.4.2Makeup 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 501.4.2.

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 501.4.2. 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 501.4.2 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.

501.4.2.1Makeup air ducts. Makeup air ducts shall be constructed and installed according to IMC chapter 6 and section 501.4.2.

501.4.2.2Makeup air intake. Makeup air intake openings shall be located to avoid intake of exhaust air in accordance with IMC section 401.4 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.

501.4.2.3Makeup 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.

501.4.2.4Makeup 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 appliance manufacturers installation instructions.

501.4.2.5Separate 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, subject 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.

501.4.2.6Makeup 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 appliances.

501.4.3Additions, 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 section 501.4.2, makeup air quantity shall be determined by using Table 501.4.1 and shall be supplied according to section 501.4.2 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 Table 501.4.1 and shall be supplied in accordance with section 501.4.2 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 Table 501.4.1 and shall be supplied according to section 501.4.2.

Exception. If a closed combustion solid fuel burning appliance is installed with combustion air in accordance with the manufacturers 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 Table 501.4.3(1) and shall be supplied according to section 501.4.2.

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 Table 501.4.3(2) and shall be supplied according to section 501.4.2.

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 Table 501.4.3(3) and shall be supplied according to section 501.4.2.

Exception: If a closed combustion solid fuel burning appliance is installed with combustion air in accordance with the manufacturers 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, 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 501.4.1

Procedure to Determine Makeup Air Quantity for Exhaust Appliances in Dwellings

	One or multiple power vent or direct vent appliances or no combustion appliances^A	One or multiple fan-assisted appliances and power vent or direct vent appliances^B	One atmospherically vented gas or oil appliance or one solid fuel appliance^C	Multiple appliances that are atmospherically vented gas or oil appliances or solid fuel appliances^D
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) clothes dryer	135	135	135	135
b) 80% of largest exhaust rating (cfm):	____	____	____	____
(not applicable if recirculating system or if powered makeup air is electrically interlocked and matched to exhaust)
c) 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]	____	____	____	____
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 501.4.2

^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 501.4.2

Makeup Air Opening Sizing Table for New and Existing Dwellings

	One or multiple power vent or direct vent appliances or no combustion appliances^A	One or multiple fan-assisted appliances and power vent or direct vent appliances^B	One atmospherically vented gas or oil appliance or one solid fuel appliance^C	Multiple appliances that are atmospherically vented gas or oil appliances or solid fuel appliances^D	Passive makeup air opening duct diameter^E,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 Air^H	>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 501.4.3(1)

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

(Refer to item 4 in section 501.4.3 to determine applicability of this table)

	One or multiple power vent or direct vent appliances or no combustion appliances^A	One or multiple fan-assisted appliances and power vent or direct vent appliances^B	One atmospherically vented gas or oil appliance or one solid fuel appliance^C	Multiple appliances that are atmospherically vented gas or oil appliances or solid fuel appliances^D
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 501.4.2

^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 501.4.3(2)

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

(Refer to item 5 in section 501.4.3 to determine applicability of this table)

	One or multiple power vent or direct vent appliances or no combustion appliances^A	One or multiple fan-assisted appliances and power vent or direct vent appliances^B	One atmospherically vented gas or oil appliance or one solid fuel appliance^C	Multiple appliances that are atmospherically vented gas or oil appliances or solid fuel appliances^D
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 501.4.2

^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 501.4.3(3)

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

(Refer to item 6 in section 501.4.3 to determine applicability of this table)

	One or multiple power vent or direct vent appliances or no combustion appliances^A	One or multiple fan-assisted appliances and power vent or direct vent appliances^B	One atmospherically vented gas or oil appliance or one solid fuel appliance^C	Multiple appliances that are atmospherically vented gas or oil appliances or solid fuel appliances
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) clothes dryer (cfm)	135	135	135	135
b) 80% of largest exhaust rating (cfm):	___	___	___	___
(not applicable if recirculating system or if powered makeup air is electrically interlocked and with exhaust)
c) 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]	___	___	___	___
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 501.4.2

^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.

Minn. R. agency 151, ch. 1346, MINNESOTA MECHANICAL CODE, pt. 1346.0501

29 SR 299; L 2007 c 140 art 1 s 1; 34 SR 537; 44 SR 1085

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