We are having a HRV or ERV installed in our house (depending on whether you look at what got installed or what's in our contract, but that's a different story). The Broan Guardian GSHH3K or GSEH3K.  My question is about the outside vent that the contractor installed, which appears to be the "tandem transition."  It's a Y-shaped vent for both intake and exhaust, right on top of each other.  Manufacturer's description (from Broan marketing material):

• Tandem(TM) "Y" shaped transition provides a single home outlet; stale air is exhausted and fresh air is drawn in simultaneously, without risk of contamination. The single hole in a home's exterior reduces product installation time, materials, and cost.
• AirDuo (TM) dual-flow, air exhaust/intake outdoor hooded air vent, plus integrated grille, featuring integral intake and exhaust filters, eliminates air cross-contamination.

It seems counter-intuitive to me that taking in fresh air and exhausting stale air right on top of each other doesn't at least partially defeat the purpose of ventilating. I would have thought these would have been mounted several feet away from each other, perhaps even on different sides of the house. I don't want to rely on filters to prevent cross-contamination.

So I'd like to ask if anybody has experience with these -- do they work as advertised, or should I insist upon a separated intake and exhaust duct before they close up the ceiling?

Did the installer put the AirDuo Exhaust/intake air vent on the exterior of the house.  That part looks like it take the intake from the bottom and exhausts out the front point up.  I've never used it, but it looks like it might work.  One comment indicated less than 3% cross contamination.  Now if they just put those two pipes outside the house with nothing else, that probably wouldn't work well.

You can see more on the AirDuo at http://www.broan.com/ImageLibrary/broan/pdf/Specifications/99044548A.pdf.

Good luck,
Bruce

Yes, they installed the Air Duo as well. I spoke to our project manager again at the HVAC contractor and he indicated that not only does this work, but it helps prevent condensation from freezing in the intake... sort of on the same principle by which the HRV/ERV works. (The outgoing air will still have some heat, and help heat the incoming air duct because they're run right next to each other.) This install is in Wisconsin so we are a heating-dominated climate and this seemed to make sense.

My HRV installation manual says they should be about 6 - 10 feet apart.

I think putting them so close seems questionable.

I like the idea of a single hole, but as Todd said I don't see how they outgoing and intake air won't mix some. In our last house there was no inexpensive way to not get them close to one another. They were about 3 feet apart and the exhaust was about a foot above the intake and the intake was usually up-wind of the exhaust. And still there were times you could smell something in the intake air and when it was really cold out and you could see the "steam" sometimes you could see it waft over to the intake. In this house I have them about 20 feet apart and around a corner from one another.

I suppose if you do get some mixing, it is WAY better than no fresh air and the exhaust air will be warmer and tend to rise pretty quickly.

I would use 10 ft.at a minimum, no one would want their bath exhaust  coming back ito the fresh air intake