Hi Autumn hopefully your new home, however tight, includes an outdoor-air ventilation system. Basically, a dedicated fan that exchanges indoor air with outdoor air. Energy raters, home performance contractors and some HVAC professionals can evaluate and advise if not. For health more than humidity. There is no such thing as too tight. The tighter the better. Your descritpions sound like classic leaky, inefficient house to me. Dry, leaking winter air requiring excessive heating during the cold season and infiltrating humid summer air the wrongly sized AC, can't deal with in the warm season. Could be wrong just sayin. Strive for cooktops vented to the outdoors and if having home performance contractors out to evaluate, have them check bath vent fans. They should be exhausting at least 50 CFM, most dont. Keep the bath door closed while showering and vent until moisture is gone. Easy ways to control big sources. A lot of moisture comes from the ground which is harder to fix on existing construction. Hopefully you don't have a crawlspace and maybe a home performance contractor can make suggestions for the foundation. Exterior grading adjustments uphill of my old home have stopped basement water intrusion, keeping it much drier. For vulnerable foundations lacking appropriate finish grading, gutters should be used and maintained with reckless abandon. I feel most east coast climates require at least some summer air-conditioning, even in MI. Mini-split heat pumps are a good solution but don't settle for HVAC contractor sizing and brand recommendations. Try to find a third party to evaluate needs for load sizing and brand. One can probably lower energy bills by offsetting some of the gas-burning. Lower energy costs plus my friends in PA and uncle in WY appreciate your concerns over their well water quality from fracking threats.

Your goal of 70 degrees for all areas is not realistic due to the design of your HVAC system and architectural design of the home. The thermostat on first level is torn between 'attempting' to keeping the 2nd floor bearable without making the basement too cold. Problem is cool air falls and hot air rises. So trying to keep the 2nd floor bearable without making basement too chilly is a recipe for disappointment. The best way to accomplish what you want is called a HVAC ducted zone system. However, this solution may not be practical and if not done properly could create other problems. Often times people are shocked what it takes to rectify problems of this nature. Certainly there are those out there who will sell you anything, then slam in in any old way. This method of slam jam may work 20% of the time, until temperature extremes come. Remember it's not just about getting this to work when it's warm out, it's also about getting it to work when it's very hot out as well as when it's really cold. With that said, to do this you would need 3 zones minimum. 1 for basement, 1 for first level, 1 for 2nd floor. Each zone would have it's own thermostat with control of the equipment. By doing it this way you probably wouldn't have to keep first floor as cool as 70 degrees, which would reduce the amount of cool air to the basement due to the cool air falls principle. If the basement is open to the 1st floor, there can be spillover to the basement especially when operating in cooling mode. The basement is naturally cooler and so without heating it / it's possible the temp down there will be less than the desired 70 degrees. The other design flaw you may be up against is return air problems. If the 2nd floor doesn't have a dedicated return to the equipment this can trap heat on that floor which can cause operational problems or hurdles for the system to over come. It would be best design wise if each level has a dedicated return in which a zone system is implemented. But realize there is much more than this to properly design a HVAC zone system.

Assuming California ballpark utility rates of $1.25 per therm and 15.34 cents per kwh, a 3.7 UEF Heat Pump Water Heater is cheaper to operate, than any available gas model. I agree there are many situations that call for tankless gas but for most new construction, HPWH is now best choice. New designs can account for space requirements. Cold climates are the toughest fit, but think a good case can be made for them when incorporated into design. For existing replacements in temperate garages, large utility rooms and basements, HPWH should be the first choice. Just make sure the space matches the headroom and volume requirements. Some don't seem to make a distinction between high efficiency gas models that have fairly safe combustion venting and cheap gas models that are atmospherically or naturally vented. The only safe place for atmospherically vented models is strictly outside of the building envelope. Backdrafting so regularly, they should be illegal inside a home and someday will be. We do combustion appliances for clients that want them but will not do natural vented gas models inside the building envelope. They are a serious liability whether the home is tight or leaky. 30 years NG transition seems about right but that's for utility scale generation. Burning it inside residential homes adds too much unnecessary risk. The backdrafting issues are not compatible with efficient construction. Especially now that heat pumps are cheaper to heat with than NG in most utility markets. ETA: I appear to be way off with current ballpark CA utility pricing. At 19 cents per kwh and $1 per therm, NG is cheaper to operate assuming high efficiency units. Sorry CA! That's ignoring monthly utility fees and reduced cooling loads which if included, could make HPWH the better investment. Agree with David that NG is artificially low there compared to electric and is likely to change soon. ETA 2: Digging deeper into average CA prices, 1.25 per therm may not be too far off. Lots of regional and yearly variances in that state. In San Fran's current market, the Prestige beats NG but in San Diego it does not. Let's just say it's competitive there, for now.. :)

I'm worried about the water line going through the cinder block basement wall, being exposed to the exterior temperatures (ie. -20) and then running up into the porch through a hole in the floor (am I getting this right?). I would not do it this way. I would spend the money to run the water line through the INTERIOR of the home. As FAR AWAY from exterior temperatures as you can. You will need to GUT the inside of the porch down to the studs (even to the point where you see the dirt below your feet while balancing on the joists). You can then enclose the raised deck as much as possible and insulate it to R40 or more. You vapour barrier this thing to within an inch of it's life. Stuff every crevice with expanding foam insulation caulking. You then insulate the FLOOR of the porch. Get as much insulation into those joists as possible (someone's getting dirty). Fix ANY weak joists or any water damaged materials as you go (add 30% cost over run just for this...if you don't need it then you don't spend it...but be prepared for the absolute worst case scenario possible = lose the entire porch). Now you install backer board and heating mats on the floor (in-floor radiant heat mats) that are then covered in tile. You will also add a baseboard heater for the space. The two run on low will have no problem keeping the space above freezing...but don't expect a nice warm space to fold laundry. You will also change out windows to the highest level you can afford. The same with the exterior door (go as high-end as you can with as much weather proofing as possible). You will stuff the walls with as much insulation as you can get in there (or better yet you can use the spray on purple stuff used for moisture protection and insulation). You will stuff the ceiling with as much insulation as you can get in there (remember I said down to the studs...no drywall or ceiling left in place). Resurface your space and keep going. And all of this hangs on the one detail no one has asked: Is this porch allowed to be there in the first place? Did anyone (you or the previous owners) ever pull permits to allow this addition in the first place? If not, your project is moot. Best start with the city and see if that porch is allowed to be there. And then check to see if it was ever allowed to be 'enclosed' and then check to see if it is allowed to become a heated indoor living space.