Hi all-

Hoping to get some input on my build-

New home this year. Radiant heat and no AC = no ducts

This is Northern MI.

Looking at an HRV in the basement. Connecting 4 bathroom vents (2 in Master bath, 1 in the other two). I'm just pulling air from bathrooms and dumping fresh air in living area in 2 spots. Not looking to have a supply to each room at all.

Question: How many air exchanges per hour should I guestimate for system sizing, assuming I have the blower test to get my "infiltration credit?"

Still 0.35 changes per hour, essentially?

The new ASHRAE 62.2 really is a lot to calculate

Thanks!

Schematic of the proposed layout.

shared ductwork can lead to sound transfer between rooms, so run them seperarely for a distance.

Thank you Bob.

Which section of duct would you call shared? I had assumed most of this would be insulated flex.

The upstairs bath lines exhaust through the ceiling then curl down through a wall to the HRV in the basement. 3600 sq ft rated SHR1505R

so youre running 4" flex seperately to all outlets? Seems like it would have a lot of resistance and poor air flow. Most use solid duct.

Thanks again, Bob. Solid it will be, then.

I could pull from the baths with 4" or 6". If 6", I could go round / rectangular and use the inside wall stud cavity to get downstairs. Maybe? 4" round seems limiting during a shower.

UPDATE:

I used an online ASHRAE 62.2 2013 calculation tool, and guestimating the door pressure test infiltration, I get a mechanical ventilation rate of between 100 and 110 CFM required.

looking at the photo of the schematic above, and the Fantech HRV SHR1505R data below, I think this will work. Assuming 0.2 to 0.4 resistance in the lines.



This would work if I could zone the different bathrooms so they are all not exhausting air when only 1 is showering.

Really, thanks Bob