What do you think of this? It’s a filtered opening that draws exterior air into the HVAC system. Haven’t seen that before and so reported for further eval. HVAC contractor states “that’s how the system is design to get outdoor air when the indoor temperature is 65 it’s grabbing fresh air.” That doesn’t make sense to me. I would think you would want a forced air system to be a “closed loop”.
Fresh air intake has been in use for office, commercial and industrial buildings for a long time.
In residential applications, it can be helpful for indoor air quality, especially as homes are being built ‘tighter and tighter’.
Arguments are made for and against based on air quality vs operating costs.
I’m guessing you haven’t seen many new houses in the past several years. 
Fresh air intake is a requirement in most locales, provided via a variety of methods.