I have been researching SIP and/or ICF home construction. I plan to use  PEX Radiant slab and Floor heating.  I understand that I would need some sort of ventilation system due to the tightness of the home. How would I incorporate that into a home that has no "air" system? I am looking at a full cellar and 2 floors.

Thanks,
David

Good choices.  Similar to the house I'm building, though I'm not doing ICF.  For our relatively dry climate, the contractor is installing a heat-recovery ventilator (HRV) . If you live in a more humid climate, then you should look into an ERV instead. With a tightly insulated house, you'll definitely need one or the other.  If you're in an area requiring air-conditioning, don't forget to allow for that in your plans. I'm still trying to figure out my options in that area.

Guy,
I am in Northern NH. As with you, during the winter, my house will be closed up tight. I just can't see how air ducts would fit in to an open concept, radiant floor heating system.

From my other reading and speaking with my contractor, ducting is probably necessary if you require central A/C.  However, if you go with a ductless mini-split system to handle A/C you could get away without standard ducting at all.  You'll still need some small, low-velocity ducting for the HRV/ERV though.  Have a read through the forums here.  Lots of useful threads on all these systems.

I have no need for A/C. So I am trying to picture what an HRV system would look like. When you say "small, low-velocity ducting" what would that be?

David

I'm probably not using the correct term.  My contractor has spec'd a unit from VanEE that describes an HRV as "fully ducted" (in the top picture). So basically in a radiant-heated home with no A/C, the HRV would have it's own dedicated ducting.  If the home is heated with forced-air, then the HRV would share the ducting (somewhat) with the furnace.  I'm starting to speak beyond my level of expertise now though so I'll let others give a better description in case I'm off base here.

the answer is fairly simple.  build a Vertical chase large enough to accomodate an air duct .  Put the HRV in aUtility room.  Punch 2 holes in the  exterior wall somewhere for the intake and exaust from the HRV.    they  should be away from the heater and bath exausts or intakes.
fresh air comes into the the HRV, gets warmed and is then ducted into the bedrooms.  Stale air is exausted from the Kitchen, bathroom and mayby laundry room into the hrv and exausted outside the house.

The design of the house has to have chases to route HRV ducting.   Figure out what HRV you want to use and just follow the duct sizing recomnedations in it.

eric

OK I get it now. I didn't realize I needed a complete duct system, but now it makes sense.
Thanks

You will need a complete duct system but it will be much smaller than the regular forced air systems. I believe the room ducts are either 3" or 4" lines.

can you do them with PVC or do you use tin?

On HRV dedicated systems I have mostly seen flexible plastic ducting. But then again these were retrofits. On new builds you could use tin/aluminum ducting but that would increase labour cost

Flex duct has high friction and causes a lot of pressure drop, i.e., loss of performance.  Good practice is for flex runs to be a max of 6 to 8 ft with minimal bends. Sometimes it cannot be helped, however.

Bruce

I agree Bruce. just stating that most retrofit applications are with flex ducts. On new builds it's harder to see the ducting.