Aprilaire makes an air-sensing automated fresh air control,as does Honeywell and Field Controls.Any established HVAC contractor can assist you.Beyond this you should look at ERV's,energy recovery ventilators if you live in an environment consistently very hot or cold.Lyle from Lisle(HVACMD)
I applaud your approach. I agree with Lyle about getting an ERV or HRV. (An ERV does total energy including humidity, HRV just transfers sensible heat by the way.)
But first, I would want to know what your combustion air needs are and any exhaust air influences which may fight that. Ideally you have direct vented appliances so maybe those cancel-out. If you do not have them I think you should. Take combustion air out of the equation to the extent you are allowed to by code.
Have you had a blower door test to demonstrate what degree of airtightness you have? Not to rely on passive leakage, but a good blower door test will reveal a minimum make-up air standard so you at least meet that.
For louvers? I am partial to Seiho products. Nice looking round louvers. For thin-line or rectangular louvers, Greenheck is my other choice.