ASHRAE 62.2 for New Construction – How to Calculate the Required Amount of Ventilation

ASHRAE 62.2, the residential ventilation standard, is now required by ENERGY STAR Version 3, as well as the Department of Energy for all federally funded weatherization projects. If you’re in the business of HVAC systems, this should be good news for you! You have extra ammunition in selling air quality to your clients! There are a lot of ways to satisfy ASHRAE 62.2 requirements. So, it’s important that you understand exactly what is required, as well as what’s not.

If you’ve tried to read the formal ASHRAE 62.2 document, you’ll know that it’s certainly written by engineers. Which is a good thing, because those folks are smart. But, it’s not all that easy to understand. So, I’ll break it down for you nice and simple.

ASHRAE 62.2 Ventilation Types

ASHRAE 62.2 was developed with the idea of making houses healthier for the occupants. ASHRAE 62.2 aims to do so by dealing with two main types of ventilation:

1. LOCAL VENTILATION: Exhausting pollutants from a point close to the source (bath and kitchen fans).
2. WHOLE-BUILDING VENTILATION: Introduce outside air into the home to dilute pollutants found in the inside air (The same reason you’d want to roll down the window if you were trapped in a car with a chain smoker – air exchange).

It’s All About Quantity

That’s really all there is to it. But, it’s crucial that you have the correct quantity of ventilation air for each of these two categories.

Here’s how ASHRAE 62.2 breaks down LOCAL VENTILATION requirements:

1. Bathrooms = Minimum 50 cfm of intermittent ventilation or 20 cfm of continuous ventilation.
2. Kitchens = Minimum 100 cfm of intermittent ventilation or 5 air-changes-per-hour of continuous ventilation.

And, here’s how ASHRAE 62.2 breaks down WHOLE BUILDING VENTILATION requirements:

1. Take the number of people x 7.5 cfm. Use the number of bedrooms + 1 to determine the number of people. (example: 3br house = 4×7.5 = 30cfm)
2. Take 1% of the square footage of the house and add it to the number you got in step 1. (example: 1800 sqft house = 18cfm, 2200 sqft house = 22 cfm, etc.)

That sums up how to calculate the quantity of ventilation needed by ASHRAE 62.2 for a given residence. The next part of the equation is to select the right solution to ensure that you’re providing the needed ventilation in a way that satisfies your client’s needs. We’ll address that in a future post.