Airflow Air Exchange Tool | The Blue Collar Wave

Airflow · Air Exchange Tool

Customer Name

Street Address

City, State, Zip

Contact

Phone

Date

System Tonnage (AC) Enter the total cooling capacity of the AC system in tons. This is used to calculate the minimum CFM required for proper airflow. Found on the equipment data plate or spec sheet. tons

AC Application Select the application type to determine the correct CFM-per-ton multiplier. Most residential systems use Normal Comfort. High latent = humid climates. High sensible = dry climates or heat pumps.

System Heating (BTU) Enter the furnace input BTU rating — not the output. Found on the furnace data plate. Leave blank if cooling-only system. Used to calculate minimum heating airflow requirement. BTU

Furnace Type Select the furnace venting type — this determines the CFM factor used. Condensing = PVC flue pipe. Induced draft = metal flue with draft inducer motor. Natural draft = open combustion with gravity venting. Select N/A if no furnace is present.

Room-by-Room Airflow Analysis

Room Description	Length (ft)	Width (ft)	Height (ft)	Cubic Ft Auto-calculated: Length × Width × Height. This is the total air volume of the room.	Duct Type Pipe = rigid sheet metal duct. Flex = flexible insulated duct. Each has different airflow capacities at the same diameter. Pipe moves more air than flex.	Supply Duct Size (in) The diameter of the supply duct serving this room. Measured in inches. Select the actual duct size — CFM is auto-filled from the sizing chart based on duct type and size.	Return Duct Size (in) The diameter of the return duct in this room. Select N/A if this room has no dedicated return — common in bedrooms and secondary spaces with a central return system.	Supply CFM Cubic Feet per Minute of conditioned air delivered to the room. Auto-filled from the duct sizing chart based on duct type and size selected.	× 60	Cu Ft / Hr Supply CFM × 60 = Cubic Feet Per Hour (CFPH). Converts per-minute airflow to an hourly rate so it can be compared against room volume.	CFPH / Cu Ft Cubic Feet Per Hour divided by the room's cubic footage. This is the Air Changes Per Hour (ACH) — how many times per hour the full volume of air in the room is replaced.	Return CFM	Air Changes Per Hour How many times per hour the room's entire air volume is exchanged. Residential targets: Bedrooms 5–6, Living areas 6–8, Kitchens 7–8, Laundry 8–9. Color coding: green = on target, amber = borderline, red = out of range.

System Summary

All final system data in one place. Supply/return totals and balance come from the room table. Required CFM comes from your system inputs above. Both must be filled in for variance to calculate.

Awaiting data

Airflow Totals

Total Supply CFM —

Total Return CFM —

Supply / Return Difference —

Enter room data to calculate

Cooling CFM Required is based on tonnage and application type. Actual is total supply CFM from all rooms. Variance shows whether the system is delivering enough air for cooling.

Required CFM —

Actual Supply CFM —

Variance —

Heating CFM Required is based on furnace BTU and type. Actual is total supply CFM from all rooms. Shows N/A if no furnace is selected.

Required CFM —

Actual Supply CFM —

Variance —

Variance: Within ±5% — acceptable 5–15% short — investigate >15% short or over-delivering — action needed

CFM Rules of Thumb

Cooling

►400 CFM per ton — normal comfort applications

►500 CFM per ton — heat pump & high sensible heat applications

►350 CFM per ton — high latent heat applications

Heating

►Condensing furnaces — 150 CFM per 10,000 BTU input

►Induced draft furnaces — 130 CFM per 10,000 BTU input

►Natural draft furnaces — 100 CFM per 10,000 BTU input

Residential Air Changes Per Hour (ACH) Targets

Basements

3–4

Bathrooms

6–7

Bedrooms

5–6

Family/Living

6–8

Kitchens

7–8

Laundry

8–9

Office/Den

6–8

Duct Sizing Reference

Flex Duct (.05")

Metal Pipe (.06")

Linear Duct

Flex Size	Design Airflow (CFM)
5"	50 CFM
6"	75 CFM
7"	110 CFM
8"	160 CFM
9"	225 CFM
10"	300 CFM
12"	480 CFM
14"	700 CFM
16"	1,000 CFM
18"	1,300 CFM
20"	1,700 CFM

Dimensions	Design Airflow (CFM)
2.5" × 10"	40 CFM
2.5" × 14"	70 CFM
2.5" × 30"	150 CFM
3.5" × 14"	100 CFM
3.5" × 30"	220 CFM

Pipe Size	Design Airflow (CFM)
5"	50 CFM
6"	85 CFM
7"	125 CFM
8"	180 CFM
9"	240 CFM
10"	325 CFM
12"	525 CFM
14"	750 CFM
16"	1,200 CFM
18"	1,500 CFM
20"	2,000 CFM