[scottlamb]

> Also saw how the HVAC system had vents to bring in air from outside with baffles controlled by the system. Can't remember exact purpose something about helping help control humidity as well as regulation to bring in "fresh" air to mix with the "stale" air in the building.

One reason is efficiency. In the Bay Area, it's common when the daytime high temperature is 80–90˚F for the nighttime low to be 50–60˚F. You can set your thermostat to 76˚F until sunset, then bring in outside air to cool down to 68˚F or below by sunrise. You get cool air when you're trying to sleep and avoid running the AC in the night or morning.

I'm getting my furnace & AC replaced today and was sad to learn I couldn't get one of these. The fresh air intake has to be at least 10' from the furnace flue vent, and that isn't practical with my home's design.

[Scoundreller]

Can’t you run a pipe outside to extend the distance of your cold air intake?

[scottlamb]

The HVAC folks didn't seem to think that would be possible/practical. I don't know exactly why. It'd have to run along the top of the roof because I don't have an attic.