I am looking at designing a house (who knows if it will ever be built....trying to figure out if building a home I want with my specs is about the same price as buying a similar one without my specs, should I have to move) and have stumbled across the ERV/HRV questions. I understand what their purpose is and what they do (the main idea is that they bring in fresh air into a tight house) and I understand how they vary from one another (one uses the heat recovery, so the intake air is close to the same temp as the outgoing air while the other helps control humidity), but the idea of them seems to be a little contradicting with various other systems in the house, particularly various heating and cooling options that people tend to cut out in order to either save monthly energy costs or to build a little "greener". It should be noted that so far I am almost decided on ICF for my plans. So here are my concerns, I hope you can help.
1) Use of ERV/HRV with radiant heating system: Reason 1 for radiant heating system is so you don't have moving air, yet by adding the ERV/HRV, you create moving air. Seems somewhat contradictory. Reason 2 for radiant heating system (hydronic) is to use less electricity, but then you turn around and use electricity for the ERV/HRV. Reason 3 is to become more "green", to use less resources, or at least waste less, which is commendable, however, I don't know that this combination does that, which is why I'm having the questions. Assumption is that the ERV/HRV uses the same ducts that is needed for the air conditioning, is this correct?
2) Use of ERV/HRV with geothermal based electric heat pump: Reason 1 for Geothermal is because the heating of the water to the required temp will cost less on a monthly basis, because it requires less energy to heat from 70 degrees (I believe that to be the output temp of the geothermal portion) to 100 degrees (heat exchanger requirement) than what it does from 50 degrees (assumed cold water temp for fresh water entering the house) to 100 degrees (heat exchanger requirement). The "Green" portion is that it requires the homeowner to use less energy on a monthly basis. However, you still need a water pump for the geothermal water to get into the house and the ERV/HRV still requires electricity, as does the heat pump (to heat the water and to blow the hot air through the ducts). Does the ERV/HRV work into the same ducts used for the heating/cooling? If so, do the two systems run at the same time, possibly forcing more air than needed into the ducts? The end result of the mixing of the two air cycles is that the hot air from the heat pump will lose some heat from the not so hot air from the ERV/HRV (remember, the air from these systems will be below room temperature) before it even gets to the room, meaning the electric pump will have to run a bit longer to get that final temperature to the thermostat setting in the air return.
3) Use of ERV/HRV with high efficiency gas furnace: Reason 1 for high efficiency gas furnace is that it burns more efficiently than other gas furnaces. Reason 2 is that it is generally a cheap option. The condensation can be used to add humidity to the house, if needed, or discarded if not needed. Again would the ERV/HRV, use the same ducts as the furnace? If so, the same question as above applies. If not, options can be added to these furnaces to help monitor air quality, which I think would make the separate ERV/HRV system redundant and therefore a waste of electricity.
4) Should ERV/HRV require their own ducts? Out of all the various things that would need exhaust in a house, I can't think of any that would be good to link with the ERV/HRV except maybe the bathroom ventilation. Any natural gas/propane or wood burning exhaust, I would expect, would require it's own exhaust so the various chemicals would not leave any residue/creosote build up in that exhaust duct which could be a fire hazard. The same for a stove exhaust, as grease would build up and the lint from dryers could cause a fire hazard. And indeed, any of these things would shorten the life of the ERV/HRV fans.
5) A little off topic, but can geothermal heating produce hot enough water to use in radiant flooring? If so, that would be a great way to recover a lot of costs....not having to pay to heat the water.
I understand that decent indoor air quality is a must, but I wonder if perhaps what we initially believe as lowering our bills is really just allowing us to pay for an additional system. What seems to be the payback of the HVAC and Air Quality systems combined? Is anyone actually saving money running both of these systems combined compared with their bills before? How much of that savings is due to the savings from the rest of the construction (air tight ICF's, SIP's, a lot of extra insulation, better windows, etc.)? Yes, you can call me a critic of new technologies, but I really just want to do what's best for my pocketbook and if a new technology saves the gas or electric company a few bucks (less production needed), it should save me a few bucks as well, as opposed to just shifting cost from monthly to upfront. Which is why I'm asking, because I don't know if it's really needed, which cases it's needed, which cases it isn't; or if it is just something people want for their own comfort level. That way, when I deal with a contractor (with HVAC needs in any house, bought or built, the contractors try to sell ERV/HRV systems) I can better understand whether I need it, or whether I will want it (distinct difference which will be needed to address financial concerns).
P.S. Before anyone starts calling me a critic of efficiency needs and "green" building, let me add that I am a critic of "green Building" because there is no real definition of "green" it is a buzzword for salesmen to use on the simple minded. And, all this would be unnecessary, if, we could make a geothermal steam generator for the residential market (using a heat exchanger and closed loop system with a low boiling point fluid in order to create electricity).
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HRV/ERV + HVAC Feasability 
Re: HRV/ERV + HVAC feasability
