#MANUFACTURERS RECOMMENDED CFM AIRFLOW PLUS#

It addresses the often-overlooked “V” in HVAC – ventilation. Room size: 400 square feet with 10-foot ceilings, or 4,000 cubic feetĪir change frequency: We want the air changed every 12 minutes, so ACH = 5ĭoing it by hand, we use the CFM formula, CFM = Area x Height x ACH / 60Ĥ00 (area) x 10 (ceiling height) x 5 (desired ACH) / 60 minutes = 334 CFM – What is It In HVAC?Ĭubic feet per minute, or CFM, is a measurement of how much air a fan moves. Try various inputs to see how the data changes as you change room size and necessary ACH – air changes per hour. You can check this example with the CFM Calculator above. The number of CFM needed to achieve the desired ACH will display automatically.Īgain, our CFM Calculator, like those the pros use, converts the number of ACH desired into the minutes it takes per air change and uses the number of minutes an air change takes in the calculation. That’s the simplest approach, and your result will be accurate. If it is a vaulted ceiling, choose a height about halfway up the slope. If the room is L-shaped or has a bump-out in the middle, then measure and multiply each rectangle separately and add them together. Measure the length times the width to get square feet. Let’s walk through this calculator together. The equation would be:Īll the calculators you find online, including ours, “do the math” for you by converting how many ACH you desire into how many minutes per change.Īll this is explained fully as we go. If the room is a living room, and 5 ACH is enough, then changing it every 12 minutes would be right (5 x 12 = 60).

This is because airflow is in CFM-cubic feet per minute, and you want the air to change every 6 minutes. Note that the minutes required for the air to change once is the important number. You want the heat and humidity gone…ĪCH (air changes per hour) Desired: 10 ACH, or every 6 minutes.įor the kitchen to remain comfortable, the HVAC ductwork would need to deliver 400 CFM of fresh air. Think lots of heat and possibly some moisture vapor from boiling pasta.

#MANUFACTURERS RECOMMENDED CFM AIRFLOW PLUS#

And there are step-by-step calculations and examples plus charts.īut here’s a quick example. Let’s say you have a 15 x 20 kitchen with an 8-foot ceiling height, and you’re cooking. The concept of ACH, or air changes per hour, is totally explained below. This is the answer to the question: How many CFM do I need to give me the right ACH? The CFM rating applies to heating too. At 350-400 CFM per 12,000 BTUs of heating capacity, there’s enough airflow to circulate heated air through supply ducts and pull cool air back to the furnace or air handler through the cold air returns.Ī 3-ton unit, or 36,000 BTUs, would need a blower capable of moving 3 x 350-400 CFM, so a total of 1,050 to 1,200 CFM.Īnswer #2: The CFM needed for a specific room depends on the size of the room and how often you want its air to be changed. Residential systems range from 1.5 to 5.0 tons, or 18,000 to 60,000 BTUs. This answer of 350-400 cubic feet per minute for each 12,000 BTUs of AC cooling is optimal for the system to run efficiently while adequately cooling and dehumidifying the space. That’s the answer to the question: What CFM do I need for my HVAC system to do its job? How many CFM do I need?Īnswer #1: 350 – 400 CFM per ton of HVAC capacity. From there, you can determine if your current system is powerful enough to meet the airflow and air changes needs in your home. The Pick HVAC CFM Calculator is featured – and it gives you the ACH number you’re looking for. How many CFM are needed to achieve the right ACH?.What types of equipment does CFM apply to?.Indoor Air Quality and Air Changes per Minute.CFM Calculator: How Many CFM Do I Need?.

Manufacturers recommended cfm airflow