I inspected a home today that had a small duct from the exterior “front porch area” to bring air into the return at the air handler. In the area I live in this is common only if the attic has spray foam to help in bringing fresh air into the home. However, i have never seen this before on a home that does not have spray foam in the attic area. Please give me some Insite on this. Not sure if it matters or not, but there appears to be a thermostatic controlled system in the middle of the duct.
Need to see additional pictures of this duct and further away pic’s in the attic space. Also, the air handler
I don’t have any more pictures of it, but I can tell you the left side is coming from the front porch, and the right side is going directly to the air handler. In addition, all rooms have a return vent as well as the supply vent.
What you’re describing is a fresh air intake, typically routed to a grill or opening (porch, etc.). It’s used to introduce fresh air into the interior of the building. Often, there is a separate ERV or dehum unit of some sort also installed unless the unit has it’s own. Can’t just dump hot humid air into the system without managing the moisture and temperature.
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Exactly, I understand that. But it’s not common to see this type of installation on a home that doesn’t have spray foam installed, “incapsulated attic” In my area anyway.
An encapsulated attic is not required to have a fresh air intake.
Typically a tight house is what pushes that need. We do it regularly up here.
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The encapsulation is only part of the equation, but I think you are on the right track. The “tighter” the home, the less fresh air will be admitted, therefore it’s a good way to compensate for all the air being vented out via bath fans, range hoods etc. Required in some jurisdictions. It also improves air quality. Slightly positive air pressure is good in my opinion.
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What year was it built? Where is it located?
I am a little confused. My understanding is th return duct system draws air from inside a home, filters it, and then sends it back to the air handler for conditioning (heating or cooling) and redistribution.
AHU gas-fired or Electric?
Model + Serial numbers please.
Why would that be?
The HVAC is a dehumidifier, why put another one on the unit?
An ERV is to control heat, not dehumidify.
It keeps the humidity out because it never lets the OA into the building.
This is an ERV. It has four pipes, two for IA and two for OA.
What you posted is misleading by the vendor. It talks about exchanging IA/OA which it can not do. It pushes air in and lets it find it’s way out through other building openings.
Greg: Why this thing is piped into the return has only one purpose. To overcome static pressure loss in the duct if it is too long, or overcome positive IA pressure.
What you have in your area has become standard to control indoor ventilation.
Introducing OA to the building should always come through the HVAC to control heat and moisture.
If they are pushing OA through the HVAC unit during the off cycle, that is wrong. In the cooling mode, it pushes moisture (condensate) back into the building after it just took it out.
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Bingo!
Ain’t It The Truth