Fresh air

What do you mean by "fresh" air?

You have to understand the big difference between "cold" air and "outside" air. This is fundamental!

Controlling the temperature in you studio is a good thing.

Being heating or cooling, it still does not mean that you renew the air in your studio.

Every person in a room is "using" oxygen to breath. This used air needs to be replaced.

One person needs about 30m3/h (cubic meter per hour) or [18cfm (cubic feet a minute)].

In "normal" rooms (office or apartment) there is a natural air exchange due to doors and windows being opened from time to time and through people circulating. In recording studios, doors and windows are closed and usually well sealed to keep the noise out.

In a sealed studio, it is necessary to force air circulation.

A minimum of 17m3/h [10cfm] per person in the room should be reached.

Air exchange can also be rated by telling how often the equivalent of the total room volume is exchanged in one hour.

That unit is called ACH (Air Change per Hour).

A minimum of 0.5 ACH should also be reached.

See the following animation about using mufflers: