First of all this is my first post in this great forum. Been reading many threads here, but the more I read the more I am confused...
Here's my situation. We are building a house in Fremont, California. Weather here is fairly mild (average summer temp highs is around high 70s to low 80s, go up to the 90s maybe 1-2 week the most. It's fairly dry here so humidity is not a problem. The house is about 4300 sq ft of living space, 3 stories on a steep hill, with the lowest being the garage, main level and the upper level is about the same size (~2100 sq ft each level). And because we are on such a steep slope, the house is step like stairs and with crawl space.
Now to our HVAC questions. On the heating side, we planned to install radiant flooring. We do need an AC system, but I am thinking about the ductless system (like mitsubishi or the Daikan), since our thinking is that by doing this we can get away with ducting, and these ductless mini split system seems very efficient and well build. On the other hand, I have read that people seem to use the ductless more for smaller space and/or retrofit. Is it a bad idea to eliminate all ducting for a new construction? Budget is also a big factor here, and it seems that the equipment itself will cost more for the ductless system, but I am hoping the installation cost will be cheaper and therefore the total installed cost will be less. Is that true?
So I am thinking either:
1. Full ductless mini split system for the whole house with various zone control. I like the ability of cooling each zone individually, and with no duct work I am hoping the total installed cost will be less than a typical ducted system. In addition no ducts sounds great as my floor plan on the main floor is very open.
2. Get a typical system with two condenser units. One will be located in the attic for the upper floor. The other one will be in the garage level, have the duct work in the garage ceiling so that the main floor air vent will be on the ground (so that I don't have to run the ducts through the main floor). Not sure if this system will cost more because of all the ducting work, and not sure how a unit in the attic will work (noise, venting to the outside, etc).
Some concerns I have with the ductless system is that, if I don't have any ducts, how do I get the systems for enhancing indoor air quality? I have read about these whole house fan, ERV/HRV, electronic air cleaner, circulating fresh air throughout the house, etc... Do all these need a duct systems? How does a ductless system do that? In addition, people seem to recommend sealing the house as tight as possible (using spray foam), but that also means I need some fresh air to circulate the house. Can you open the windows to achieve similar effect?
Lastly, can you tell me some rough system cost comparison between the mini split ductless and the traditional AC system? I know it varies, but I want to get some ideas before I go talk to contractors. Is there some HVAC contractors recommendation in the San Francisco Bay Area? There are just so many contractors but not sure which is good (both quality and value).