Since we had to forgo the radiant floor system, we’ve had to get serious about what we will be using for a forced-air mechanical system. We will be using a high-efficiency furnace (90% or better). Instead of using the “rule of thumb” type sizing, the more thorough “right sizing” or “Manual J” method will be used. In addition, we will hopefully add third party testing - blower door and duct leakage.
We are still on the fence about using the traditional compressor-based air conditioning unit (granted it would be high-efficiency - 15 SEER) or go for an efficient indirect swamp cooler. The trouble is we haven’t found a cost efficient method for combining these two very different systems.
For domestic hot water, we will be using a gas fired tankless water heater (on-demand). I think we will start with just one for the entire house, and probably rough-in for a second, considering we are also prepping for a future guest suite on the basement level.