These are "nutshell" answers since envelope issues are tough to diagnose over the internet. The HRV is an exchanger, but if your house is tight and your winter interior humidity is high, it'll exchange stale humid interior air for fresh dry exterior air while minimizing heat loss during the exchange. A blower door test is usually part of a more comprehensive analysis which could run a few hundred dollars. $200-$400 depending on the thoroughness of the inspection. If your house is excessively tight then it might make sense to install make-up air duct for the furnace. If you have an HVAC company out there, often times they'll do envelope and blower door tests. With all the "green" garbage going on, there are a lot of folks jumping on the bandwagon just as "energy consultants." If you're going to have work done, many companies will credit the cost of the blower door test and other analysis towards the cost of future modifications. Backtracking and peeking at the larger picture, basements can be a source of moisture vapor. Moisture vapor and maybe even liquid through rubble foundations, or vapor through poured concrete or block foundations. Think of it this way: You tightened up your house, which lessens moisture removal, but if your basement is a source of moisture vapor, it's still adding moisture vapor to the house. If it applies to you, a good thing to do is to minimize as best as you can air movement from the unconditioned basement into the conditioned living space above. Go in the basement and look up. Any gaps in the basement ceiling that lead into the house above (plumbing penetrations, electrical penetrations, hvac penetrations, etc) can be sealed with canned foam. It makes sense to do the same thing in the attic floor if the attic is unconditioned. The goal is to keep the conditioned air that you're paying to condition within the thermal envelope of the house. It's not a sexy job, mostly elbow grease, but walking and crawling around your house and shooting gaps with foam can have great effect. With those DIY cans of foam like Great Stuff, it's best to uncover the gaps first, then fill them all at once. Ling delays between trigger actuations can allow foam to cure in the nozzle.

OK...problem is now resolved (I think). I managed to get the cover and light fixture out of the unit, then removed the fan assembly to see if I could see things better. There is a contra-flow "flap" that was stuck in an open position. I could close by pushing it shut with a screwdriver, but then when I opened it again, it stayed open. Perhaps some lint build-up or something like that, but anyway, there was a plastic tab that is to act as a counter-balance to make the thing shut again so I attached a small paper clip type thing to it to give it just an extra bit of weight. Now when I push it open with a screwdriver, it opens and then closes back on it's own. As for the venting piece, I really can't see if it's venting directly into the soffit, but I suspect you are right. It is so far back into a corner of the house, it's virtually impossible to see. Thanks to all for your help and advice. I love this kind of teamwork.

Bathroom fans move much less air than a whole house fan. I don't think you will have a problem. If the bathroom fan is going to be used to remove moisture after a shower then I suggest wiring it to a timer. Running the fan for 20-30 minutes during and after the shower should be sufficient.

As for fan-lights in the shower, it seems ineffective to try to remove water vapor laden air from the shower since most of it will condense on the walls before that can happen anyway. My goal is to remove humid air from the vanity area and allow fresh air drawn from the door undercut to reduce fogging of the mirror and window glass. The entire bathroom will eventually dry out if you use a fan with a built in timer and/or constant low speed feature like Panosonic's WhisperGreen series. I have yet to find a fan-light combination that performs as well as separate units. Here are my criteria: no CFL or LED lamps (LED inappropriate in a bathroom; CFL inappropriate in a house) Max sound rating .8 sone max grille size 13x13 flush with ceiling variable speed fan with timer Panasonic makes a recessed spotlight-fan combination (FV08VRL1) but it uses a CFL. I suppose a halogen PAR lamp could be substituted because the CFL is probably only needed to get an EnergyStar rating but I am not comfortable recommending it. To reduce fan noise it is important to reduce back-pressure by using larger metal ducts.