We're building a 4 bedroom, 4300 square foot new modular home in southern NY (Long Island). 2 story colonial with full basement. All ductwork and mechanicals are done on-site, and I've been trying to understand ventilation options. We intend to use in-floor radiant heat throughout the heat, and install central air (variable speed air handler, 2 stage compressor) and provide for ventilation. One family member has recently developed severe and debilitating allergies, identified as tree pollen and dust mites, so IAQ is a big issue. Buildingscience.com identifies the climate as cold. It is cold and very dry in the winter, and hot and humid in the summer. AC will run from May to September, heat from October through April. Often in summer, the nights are cool and very humid, so it is important to be able to dehumidify without cooling. Building Science seems to advocate supply ventilation through the return of the air handler, but I don't see the logic in introducing very cold air in the winter (hydronic heat, so the air handler is not a furnace), and very humid air in the summer through this method. Plus, it doesn't seem like a good idea to induce exfiltration of humid air into the building structure. We don't mind paying a little extra for better efficiency and comfort. It seems to me the most complete option would be the use of an ERV year round for ASHRAE ventilation standards to prevent over-drying of the house in the winter, and introduction of very humid air in the summer, a whole house dehumidifier to control moisture when necessary, and a separate supply-air method with some sort of differential pressure control solely for powered make-up air (perhaps up to 1000CFM?) to keep the house pressurized to about 5 pa. The air handler would cycle periodically for proper air mixing and high efficiency filtration.

Does my setup seem reasonable? Any suggestions?

How good is the Carrier infinity system at controlling Humidity with low cooling loads? The system seems very interesting, but probably not worth it since I'm wouldn't be using any compatible component other than the compressor and air handler, and probably need a separate de-humidifier anyway.

I am a bit confused as to whether to use an ERV or an HRV. Each manufacturer seems to have different propaganda. Some claim an ERV is appropriate everywhere except the extreme north. Some claim an ERV is only appropriate in the very south. It seems silly to me to us a product that can only operate in one season, and and HRV would be useless in the summer, since it would be pumping massive amounts of humidity in the house. And I'm afraid of it over-drying the house in the winter. The ERV seems better, but some manufactures claim they can't be used in weather that will drop bellow 25. It happens some in my climate, but not much. The average low in the coldest month is 26. Do differing methods of ERV manufacturing make this true for some and not for others?

This is a very complicated field, with lots of different and often conflicting approaches and suggestions. Thank you for your time and thought.


[Edited by sibellc on 04-23-2005 at 12:56 AM]