I built my own home, subcontracting major parts and building the rest myself.  I'm in Phoenix, AZ and built a single-story home with ICF walls (Arxx) and had Icynene sprayed onto the underside of the roof decking (truss roof).  This is our the start of our third summer, and we've noticed an odd sort of "sweet" smell when the house is closed up for the day.  We have the AC vent fan running constantly, but do not have an air exchanger.  I had a local HVAC company come in with an air tester for several days, and no VOC's or other harmful elements were present in our air.  Has anyone else had this situation or heard of this?  It only seems to happen when it is warm outside, although when it's cooler we generally open the windows frequently.  I just want to make sure that this will not cause any health issues, and what I should do.  I'm wondering if having an air exchanger put in will clear things up?  I just want to make sure because I was quoted $1500, and I don't want to spend the money if it won't fix this issue.  Thanks for any input.

if your attic is sealed (dry wall), there should not be any vapors from the foam in the house.
foam will smell for a few days or weeks at most
icf and foam make for a tight house, any "smell" from air fresheners, candles, ect will be exaggerated

mac

You need an air exchanger for sure. Your house is to tight. It is either open windows or put in an air exchanger. Just built a green home and used ICF and Soy base ISO foam and Geo thermal with the air exchanger built in. The house is great.

I think mac is on to something.
Any odor that is in your home will remain for extended periods.
If the odor is constant, then look for an agent that is always open, air freshners or such.
If the odor changes from time to time, it could be any number of thing, cooking odors, fruit setting in a open bowl, laundry products, the list goes on.
Your AC fan simply recirculates the odor throughout the whole house.
An air exchanger would be a good idea. Even if the house is only closed up a few days at a time, you still need to introduce fresh air on a regular basis. Plus with the pickups located in the kitchen, laundry, bath areas, the most likely odor laden air will be the first removed.

Does your attic smell different from the living space?

Bruce

Thanks everyone for the responses.  Does $1500 to retrofit an air exchanger onto my current system seem typical?  As for the attic smelling different than the home, it's hard to tell because you get the strong odor when you first arrive, then you don't notice it much after that.  I think my nose just gets used to it.  I might try plugging my nose next time I gethome until I get in the attic to check it out.  What would it mean if the smell is the same/different?  Thanks.

If they are installing an ERV for $1,500, that sounds like a good price to me.  Look at ERV's on the net and you'll see some that cost more than that.  You probably need to confirm what they are installing.

If th smell is different (stronger/weaker), it may tell you where the source is.

Bruce