1446 Dolores Lane - Ventilation Calcs 2021-03-31Ventilation, Makeup and Combustion
Air Calculations Submittal Form for New Dwellings
Site Address Date
Contractor Completed By (please print)Signature
Section A
Ventilation Quantity
(Determine quantity by using Table R403.5.2 or Equation R403.5.2)
Square feet (Conditioned area including
Basement – finished or unfinished)
Number of bedrooms
Total required ventilation
Continuous ventilation
Directions - Determine the total and continuous ventilation rate by either using Table R403.5.2 or equation R403.5.2.
The table and equation are below.
Table R403.5.2
Total and Continuous Ventilation Rates (in cfm)
Number of Bedrooms
1 2 3 4 5 6
Conditioned space
(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
5501-6000 150/75 165/83 180/90 195/98 210/105 225/113
Equation R403.5.2
(0.02 x square feet of conditioned space) + [15 x (number of bedrooms + 1)] = Total ventilation rate (cfm)
Total ventilation – The mechanical ventilation system shall provide sufficient outdoor air to equal the total ventilation rate
average, for each one-hour period according to the above table or equation. For heat recovery ventilators (HRV) and energy
recovery ventilators (ERV) the average hourly ventilation capacity must be determined in consideration of any reduction of
exhaust or out outdoor air intake, or both, for defrost or other equipment cycling.
Continuous ventilation - A minimum of 50 percent of the total ventilation rate, but not less than 40 cfm, shall be provided,
on a continuous rate average for each one-hour period. The portion of the mechanical ventilation system intended to be
continuous may have automatic cycling controls providing the average flow rate for each hour is met.
Page 2 of 6
Section B
Ventilation Method
Balanced, HRV (Heat Recovery Ventilator) or ERV (Energy Recovery
Ventilator) – cfm of unit in low must not exceed continuous
ventilation rating by more than 100%.
Low CFM High CFM
Directions - Balanced ventilation systems are typically HRV or ERV’s. Enter the low and high cfm amounts. Low cfm air flow
must be equal to or greater than the required continuous ventilation rate and less than 100% greater than the continuous rate.
(For instance, if the low cfm is 40 cfm, the ventilation fan must not exceed 80 cfm.) Automatic controls may allow the use of a
larger fan that is operated a percentage of each hour.
Section C
Ventilation Fan Schedule
Description Location Continuous Intermittent
Directions - The ventilation fan schedule should describe what the fan is for, the location, cfm, and whether it is used for
continuous or intermittent ventilation. The fan that is chose for continuous ventilation must be equal to or greater than the
low cfm air rating and less than 100% greater than the continuous rate. (For instance, if the low cfm is 40 cfm, the continuous
ventilation fan must not exceed 80 cfm.) Automatic controls may allow the use of a larger fan that is operated a percentage of
each hour.
Section D
Ventilation Controls
(Describe operation and control of the continuous and intermittent ventilation)
Directions - Describe the operation of the ventilation system. There should be adequate detail for plan reviewers and inspectors to verify
design and installation compliance. Related trades also need adequate detail for placement of controls and proper operation of the building
ventilation. If exhaust fans are used for building ventilation, describe the operation and location of any controls, indicators and legends. If
an ERV or HRV is to be installed, describe how it will be installed. If it will be connected and interfaced with the air handling equipment,
please describe such connections as detailed in the manufactures’ installation instructions. If the installation instructions require or
recommend the equipment to be interlocked with the air handling equipment for proper operation, such interconnection shall be made and
described.
Section E
Make-up air
Passive (determined from calculations from Table 501.41)
Powered (determined from calculations from Table 501.4.1)
Interlocked with exhaust device (determined from calculation from Table 501.4.1)
Other, describe:
Location of duct or system ventilation make-up air: Determined from make-up air opening table
Cfm Size and type (round, rectangular, flex or rigid)
(NR means not required)
Page 3 of 6
Directions - In order to determine the makeup air, Table 501.4.1 must be filled out (see below). For most new installations, column
A will be appropriate, however, if atmospherically vented appliances or solid fuel appliances are installed, use the appropriate
column. For existing dwellings, see IMC 501.4.3. Please note, if the makeup air quantity is negative, no additional makeup air will
be required for ventilation, if the value is positive refer to Table 501.3.2 and size the opening. Transfer the cfm, size of opening and
type (round, rectangular, flex or rigid) to the last line of section D. The make-up air supply must be installed per IMC 501.4.2.3.
Table 501.4.1
PROCEDURE TO DETERMINE MAKEUP AIR QUANITY FOR EXHAUST EQUIPMENT IN DWELLINGS
(Additional combustion air will be required for combustion appliances, see KAIR method for calculations)
One or multiple power
vent or direct vent
appliances or no
combustion appliances
Column A
One or multiple fan-
assisted appliances and
power vent or direct vent
appliances
Column B
One atmospherically vent
gas or oil appliance or
one solid fuel appliance
Column C
Multiple atmospherically
vented gas or oil
appliances or solid fuel
appliances
Column 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) continuous exhaust-only ventilation
system (cfm); (not applicable to
balanced ventilation systems such as
HRV)
b) clothes dryer (cfm)135 135 135 135
c) 80% of largest exhaust rating (cfm);
Kitchen hood typically
(not applicable if recirculating system
or if powered makeup air is electrically
interlocked and match to exhaust)
d) 80% of next largest exhaust rating
(cfm); bath fan typically
(not applicable if recirculating system
or if powered makeup air is electrically
interlocked and matched to exhaust)
Not
Applicable
Total Exhaust Capacity (cfm);
[2a + 2b +2c + 2d]
3. Makeup Air Quantity (cfm)
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
A. Use this column if there are other than fan-assisted or atmospherically vented gas or oil appliance or if there are no combustion appliances. (Power vent and
direct vent appliances may be used.)
B. Use this column if there is one fan-assisted appliance per venting system. (Appliances other than atmospherically vented appliances may also be included.)
C. Use this column if there is one atmospherically vented (other than fan-assisted) gas or oil appliance per venting system or one solid fuel appliance.
D. Use 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.
Page 4 of 6
Makeup Air Opening Table for New and Existing Dwelling
Table 501.4.2
One or multiple power
vent, direct vent
appliances, or no
combustion appliances
Column A
One or multiple fan-
assisted appliances and
power vent or direct
vent appliances
Column B
One atmospherically
vented gas or oil
appliance or one solid
fuel appliance
Column C
Multiple atmospherically
vented gas or oil
appliances or solid fuel
appliances
Column D
Duct diameter
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
w/motorized damper
318 – 419 196 – 258 136 – 179 84 – 110 9
Passive opening
w/motorized damper
420 – 539 259 – 332 180 – 230 111 – 142 10
Passive opening
w/motorized damper
540 – 679 333 – 419 231 – 290 143 – 179 11
Powered makeup air >679 >419 >290 >179 NA
Notes:
A. An 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.
B. If flexible duct is used, increase the duct diameter by one inch. Flexible duct shall be stretched with minimal sags. Compressed duct shall not be accepted.
C. Barometric dampers are prohibited in passive makeup air openings when any atmospherically vented appliance is installed.
D. Powered makeup air shall be electrically interlocked with the largest exhaust system.
Section F
Combustion air
Not required per mechanical code (No atmospheric or power vented appliances)
Passive (see IFGC Appendix E, Worksheet E-1) Size and type
Other, describe:
Explanation - If no atmospheric or power vented appliances are installed, check the appropriate box, not required. If a power
vented or atmospherically vented appliance installed, use IFGC Appendix E, Worksheet E-1 (see below). Please enter size and type.
Combustion air vent supplies must communicate with the appliance or appliances that require the combustion air.
Section F calculations follow on the next 2 pages.
Page 5 of 6
Directions - The Minnesota Fuel Gas Code method to calculate to size of a required combustion air opening, is called the Known Air
Infiltration Rate Method. For new construction, 4b of step 4 is required to be filled out.
IFGC Appendix E, Worksheet E-1, 1346.6012
Residential Combustion Air Calculation Method
(for Furnace, Boiler, and/or Water Heater in the Same Space)
Step 1: Complete vented combustion appliance information.
Furnace/Boiler:
__ Draft Hood __ Fan Assisted Direct Vent Input: Btu/hr
or Power Vent
Water Heater:
__ Draft Hood Fan Assisted __ Direct Vent Input: Btu/hr
or Power Vent
Step 2: Calculate the volume of the Combustion Appliance Space (CAS) containing combustion appliances.
The CAS includes all spaces connected to one another by code compliant openings. CAS volume: ft
3
L x W x H L W H
Step 3: Determine Air Changes per Hour (ACH)1
Default ACH values have been incorporated into Table E-1 for use with Method 4b (KAIR Method).
If the year of construction or ACH is not known, use method 4a (Standard Method).
Step 4: Determine Required Volume for Combustion Air. (DO NOT COUNT DIRECT VENT APPLIANCES)
4a. Standard Method
Total Btu/hr input of all combustion appliances Input: ______________ Btu/hr
Use Standard Method column in Table E-1 to find Total Required TRV: _________________ ft3
Volume (TRV)
If CAS Volume (from Step 2) is greater than TRV then no outdoor openings are needed.
If CAS Volume (from Step 2) is less than TRV then go to STEP 5.
4b. Known Air Infiltration Rate (KAIR) Method (DO NOT COUNT DIRECT VENT APPLIANCES)
Total Btu/hr input of all fan-assisted and power vent appliances Input: Btu/hr
Use Fan-Assisted Appliances column in Table E-1 to find RVFA: ft
3
Required Volume Fan Assisted (RVFA)
Total Btu/hr input of all Natural draft appliances Input: Btu/hr
Use Natural draft Appliances column in Table E-1 to find RVNFA: ft3
Required Volume Natural draft appliances (RVNDA)
Total Required Volume (TRV) = RVFA + RVNDA TRV = + = TRV ft
3
If CAS Volume (from Step 2) is greater than TRV then no outdoor openings are needed.
If CAS Volume (from Step 2) is less than TRV then go to STEP 5.
Step 5: Calculate the ratio of available interior volume to the total required volume.
Ratio = CAS Volume (from Step 2) divided by TRV (from Step 4a or Step 4b)
Ratio = / =
Step 6: Calculate Reduction Factor (RF).
RF = 1 minus Ratio RF = 1 - =
Step 7: Calculate single outdoor opening as if all combustion air is from outside.
Total Btu/hr input of all Combustion Appliances in the same CAS Input: Btu/hr
(EXCEPT DIRECT VENT)
Combustion Air Opening Area (CAOA):
Total Btu/hr divided by 3000 Btu/hr per in2 CAOA = / 3000 Btu/hr per in2 = in2
Step 8: Calculate Minimum CAOA.
Minimum CAOA = CAOA multiplied by RF Minimum CAOA = x = in2
Step 9: Calculate Combustion Air Opening Diameter (CAOD)
CAOD = 1.13 multiplied by the square root of in. diameter
go up one inch in size if using flex duct
1 If desired, ACH can be determined using ASHRAE calculation or blower door test. Follow procedures in Section G304.
Page 6 of 6
IFGC Appendix E, Table E-1
Residential Combustion air (Required Interior Volume Based on Input Rating of Appliance)
Input Rating
(Btu/hr)
Standard Method Known Air Infiltration Rate (KAIR) Method (cu ft)
Fan Assisted or Power Vent Natural Draft
1994 to present Pre-1994 1994 to present Pre-1994
5,000 250 375 188 525 263
10,000 500 750 375 1,050 525
15,000 750 1,125 563 1,575 788
20,000 1,000 1,500 750 2,100 1,050
25,000 1,250 1,875 938 2,625 1,313
30,000 1,500 2,250 1,125 3,150 1,575
35,000 1,750 2,625 1,313 3,675 1,838
40,000 2,000 3,000 1,500 4,200 2,100
45,000 2,250 3,375 1,688 4,725 2,363
50,000 2,500 3,750 1,675 5,250 2,625
55,000 2,750 4,125 2,063 5,775 2,888
60,000 3,000 4,500 2,250 6,300 3,150
65,000 3,250 4,875 2,438 6,825 3,413
70,000 3,500 5,250 2,625 7,350 3,675
75,000 3,750 5,625 2,813 7,875 3,938
80,000 4,000 6,000 3,000 8,400 4,200
85,000 4,250 6,375 3,188 8,925 4,463
90,000 4,500 6,750 3,375 9,450 4,725
95,000 4,750 7,125 3,563 9,975 4,988
100,000 5,000 7,500 3,750 10,500 5,250
105,000 5,250 7,875 3,938 11,025 5,513
110,000 5,500 8,250 4,125 11,550 5,775
115,000 5,750 8.625 4,313 12,075 6,038
120,000 6,000 9,000 4,500 12,600 6,300
125,000 6,250 9,375 4,688 13,125 6,563
130,000 6,500 9,750 4,875 13,650 6,825
135,000 6,750 10,125 5,063 14,175 7,088
140,000 7,000 10,500 5,250 14,700 7,350
145,000 7,250 10,875 5,438 15,225 7,613
150,000 7,500 11,250 5,625 15,750 7,875
155,000 7,750 11,625 5,813 16,275 8,138
160,000 8,000 12,000 6,000 16,800 8,400
165,000 8,250 12,375 6,188 17,325 8,663
170,000 8,500 12,750 6,375 17,850 8,925
175,000 8,750 13,125 6,563 18,375 9,188
180,000 9,000 13,500 6,750 18,900 9,450
185,000 9,250 13,875 6,938 19,425 9,713
190,000 9,500 14,250 7,125 19,950 9,975
195,000 9,750 14,625 7,313 20,475 10,238
200,000 10,000 15,000 7,500 21,000 10,500
205,000 10,250 15,375 7,688 21,525 10,783
210,000 10,500 15,750 7,875 22,050 11,025
215,000 10,750 16,125 8,063 22,575 11,288
220,000 11,000 16,500 8,250 23,100 11,550
225,000 11,250 16,875 8,438 23,625 11,813
230,000 11,500 17,250 8,625 24,150 12,075
1. The 1994 date refers to dwellings constructed under the 1994 Minnesota Energy Code. The default KAIR used in this section of the table is
0.20 ACH.
2.This section of the table is to be used for dwellings constructed prior to 1994. The default KAIR used in this section of the table is 0.40 ACH.