all electric or nat gas is available?

tiger dunes: all electric. Would love to have nat. gas, but not available and according to the gas company, they have no plans to extend service to our area.

Austin Air: Looks like we will have 2 separate systems, one for each floor. My main question (I put it badly), is it worth the cost to install a mini split or wall unit a/c for extra cooling in the bedroom at night? Or is it close to a wash to just reduce the thermostat for the whole floor? I'm guess we use a/c about 7-8 months during the year.

I don't like the idea of a mini split expense. Look at getting a high end var speed condenser like the XV18 Trane or AmStd heat pump and have zoning controls installed.

IMO

I'll look in to that. Appreciate your input. Thanks.

Austin Air: Looks like we will have 2 separate systems, one for each floor. My main question (I put it badly), is it worth the cost to install a mini split or wall unit a/c for extra cooling in the bedroom at night?

As with everything else it depends. How big (in tons) will this second system be? If it's a 3 ton or more and you are at least going with a 2 speed compressor then I think it makes sense to zone it at least into two or 3 zones. Realize the more zones you have the better control you will have over the system in question, but also the more complicated the zoning is.

Many times a builder, when installing zoning use over sizing of ducts a method to make zoning work, when only 1 zone is calling. It will work this way, but under considerable heat loads and or the opening of all zones at once under heavy loads the system will be brought to it's knees and performance will fall off a cliff.

The reason this happens is lack of velocity thru the duct system. This kind of problem you wouldn't have with a mini split. But mini splits are complicated for a different reason... they ( the manufacturer's try to be all things to every situation) to make matters worse the technology rapidly changes and models of equipment tend to be much shorter than regular ducted systems. This can pose problems getting parts when the machine breaks. This may change as more and more American HVAC manufacturer's make this style of equipment.

Given that you are on all electric, I would look into the heat pump option. By using heat pump during winter as opposed to electric heat the savings are thru the roof on this option. Electric strip heat is expensive to operate.

As far as high end (all variable speed everything or Inverter Type System) I wouldn't limit yourself to only Trane or American Standard option. In this realm of HVAC equipment, installation means everything. If installation isn't done right, brand will not matter.

Servicing of equipment is also another important part of the equation. The last thing you want is a system that no one will work on because they are afraid of it or don't understand it.

If comfort is of most importance as opposed to cost or risk of problems associated with such, I would zone that master bedroom regardless of size of equipment... just for the sake of better control over the system. Better control = better comfort, no matter which way you slice it.

Carrier/Bryant high end var speed HP condenser with zoning controls would be OK as well.

IMO

Thanks so much tigerdunes!

Hire a residential energy rater to help you plan and supervise building. Set milestones for duct and envelope air leakage with their help and have them do testing to see that they are met. Duct leakage is not so important with interior ducts and interior ducts are very important so make that part of your design. Make sure, however that your room to room air flow is balanced so as not to cause pressure imbalances that also turn your air handler into a power vent. duct leaks can cause pressure differentials even if they are all in interior space.

Zoning with mini splits or any other way do less for energy savings in well-built homes than in poorly-built homes. The reason is that heat and humidity pass through interior spaces (walls included) much faster than through exterior walls. With a poorly-insulated, leaky building, zoning can save some coin.

A mini split is going to be an extra expense up front, maintaining it (cleaning) and for repairs. Is cost, however, everything? Comfort and noise will be much better than a cheaper window or through-wall unit. Advantages include a very low attainable output level. If you install a 6000 btu model, for example, it can probably throttle back to 2000. Most of that can be put into dehumidification on that setting in shoulder seasons to keep the bedroom and the whole house drier. That is especially helpful at night when heat gain is lowest in warm,not hot, and humid weather. Leave the bedroom door open and it is even more effective. Given the fact that zoning is not an energy saver in good buildings, open floor plans are most common and you are just the two of you sleeping in the house most of the time, you could even put it in a central area near the BR and keep the BR door open. For highest effectiveness, have a ceiling fan near because in dehumidify mode the blower is going very slowly so air circulation is not as great.

Another advantage is the ability to run it with a relatively small backup generator. I just reviewed the amperage readings I got from my dual and three-head units operating in single indoor unit mode.They use as little as 2.5 amps at full output for 6000 and 9000 btu units. This is important: These inverter-driven compressors revealed virtually no start-up surge.

Thank you so much everyone. A lot of very good information. Yes, we will have a ceiling fan in the room and hiring an energy rater sounds like a good idea. We are looking at having a backup generator as well, so this makes great sense.