I suggested that Nicks system should world like the AprilAire 8126, and he suggested that I tell him how it works. Well Nick, do some research fro yourself and find out what it does.
A simple summary is that it senses RH and temperature inside and outside the home. It interfaces to the fan in the HVAC controller. The 8126 controller interfaces to an actuator installed in a duct leading to the outside of the house, said duct connected to the return air plenum of the HVAC. The amount of time that the fan runs is user selectable. When the damper is open and the fan is running, outside air is pulled into the HVAC and distributed throughout the house. The damper will not open if the outside air temp is above 100F, and it will not open when the outside air is below 0F. The damper will not open if RH inside climbs above 55%.
It is designed to allow entry of fresh air into modern homes that are built MUCH tighter against air infiltration than houses of even 15 years ago. All to easy for bad smells to accumulate in these new houses (cooking odors, diaper odors, smoking, body oder, molds, cleaning fluids, outgassing from new construction materials......)
It does so on a controlled basis, not letting RH rise too high.
Nick lives in Pennsylvania and clearly has no idea what life is like in the Deep South. Heck we see stories nearly every year about people dying in New York City and the other big cities of the NorthEast when the high temps climb to the mid to upper 80s for days at a time. The Deep South endure MONTHS of this kind of weather and not a peep in the press about it.
Today in Villnova PA it is 72 degrees, winds are from the NE at 4mph. Humidity is running at 59% A bit on the high side for humidity, but wow what a nice temperature.
Where I sit right now, the temp is 93F, there is NO wind, and humidity is lower than normal at 49% Everyone that can is inside an air condtioned space. From now thru Spetember, nearly every day here will be a repeat of this but generally with higher relative humidity (closer to 55-65% is more typical although we see days at a stretch with 90+F and 90+RH even in the afternoon).
Nick's system appears to mimic the behavior of the AprilAir without the limit controls installed. It is unclear from my memory of his theory just how he was going to bring the air into the house, simply open a duct and let it flow naturally, or hook it into the inlet side of the HVAC and run the fan. As at least one other poster has pointed out such systems have limited application as the actuator MUST be protected from icing conditions, and in cold, cold areas, they simply get taped shut as they introduce too much cold air (drafts are induced)
In my area the question is whether the benefit of introducing fresh air outweighs the additional load on the HVAC?????????