# How is k-factor used and Vav flow calculation # How is k-factor used and Vav flow calculation?

The K-factor and vav flow calculation are two distinct types of calculations that HVAC professionals often use. The difference between the two, how they are used and who should perform each of these calculations is often misunderstood by many, including the technicians. Suppose you want to avoid confusion in the future about the two calculations. In that case, this article will help clarify everything you need to know about both so you can understand which one to use when it comes time to calculate on your own.

## What Is K-Factor (Kf)?

A common way to quantify how much water a building needs to cool itself down adequately is with the K-Factor. A higher K-Factor number represents a bigger demand for HVAC cooling. Whereas a lower K-Factor means less need for such infrastructure. The K factor can be calculated by dividing BTU/hour (BTU/hr) by cubic feet per minute (CFM). One BTU equals roughly 1055 J, whereas 1 CFM equals 0.0283 m3/sec. For example, if your HVAC system produces 3200 BTUs of energy every hour, but you have only 1000 CFMs of air supplied through it, then your K-Factor would be 3200 divided by 1000, equaling 3.2.

#### How to Calculate the K Factor?

K factor is a measure of heat transfer efficiency. This can be calculated by taking the fluid temperature at point 1, subtracting the liquid temperature at point 2, and then dividing by the difference in height between these two points. For example, take water as your fluid that flows from reservoir R1 into reservoir R2 to control its boiling point. With R1 flowing with 1000 m^3/h of hot water at 100 degrees Celsius (point 1) and R2 flowing with 200 m^3/h of cold water at 10 degrees Celsius (point 2), calculate the K factor using the following equation: \frac = 1.25 kilowatts per square meter\]

### How to Use the K-Factor in VAV Flow Calculations?

The K factor in VAV flow calculations, or volume air ratio, is one of the essential values you need to calculate how much air will be exhausted when a system has been shut down. The higher the K factor, the less air that will be finished. Knowing this can save energy costs if a significant amount of makeup airflow is required for a space’s comfort level.

The K Factor equals Air Out / Air In multiplied by 100%. In other words, divide the total amount of air being expelled by the total amount of air entering. The answer will then equal 100% to determine how much makeup needs to come into your system for each percentage of outflow reduction from your desired makeup air requirements.

#### The Importance of K-Factor and VAV Flow Calculation

You may wonder what K-Factor is or how it’s related to VAV Flow Calculation. We’ll explain the differences between the two, how they can help your business, and how you can use them. First, let’s define some of the terms to start: -K Factor is a standard industry practice for indicating the minimum rate of supply air change under normal conditions. The most common value for K Factor ranges from 1.2 to 1.5 air changes per hour. The higher the K Factor number, the less restrictive (and efficient) the ventilation system will be. S

o how does this relate to VAV? First, you need a low enough K Factor number to have sufficient airflow within the room; anything higher than 2.0 air changes per hour won’t work for this purpose. Second, because ventilating systems are typically sized based on their CFM requirements during peak periods of occupancy. There will likely not be enough capacity in these systems during non-peak hours when many people are not present. Therefore, additional controls such as VAV can optimize energy usage by adjusting these levels automatically. 