SR The new tile floor is down. We thought about electric radiant but did not have room (old house and had constraints). The kitchen is completed but we do have some space in a wall that is an enclosure that had been built to house a built-in refrigerator.

George: thanks for the response. Do I lose anything in terms of efficiency if I drop all of the A/C from the attic and is it better to the ducts then into the ceilings or should I drop them on the walls of both floors?

Agreed Bry, that's a great point. In renovation or replacement comparison situations when a household is consistently using the baseline allowance, using the next tier rate up would be more accurate. It's also tough figuring out how much of the minimum monthly gas fee to include. I would guess the water heater may account for ~50% of usage so more accurate water heater gas costs would be somewhere near $302. Much tougher figuring the added comfort and space conditioning benefits of a HPWH and if the gas combustion appliance is naturally vented, there is probably added moisture and potentially health costs involved. For new construction, not knowing specific situations I think average kwh rates are where to start, and it's only the most energy intensive homes that would recover new infrastructure costs. Those outliers might be wise to improve the design. An energy rater would be helpful for plan specific comparisons. Mr. Fudd's Tier 2 kicks in at 202 kwh, lower than baseline allowances I saw digging around on the PG&E site. It must be an energy intensive area because most Tier 2 levels I saw were higher. This suggests the averages I linked to are close. Most tier talk for PG&E (serving a third of CA households according to this page) is about to be irrelevant as they are transitioning to Time Of Use rates for everyone. This makes sense for the increasingly renewable electric grid. For example, it will encourage electric vehicle owners to charge during off-peak hours and will keep electric water heating costs competitive with gas, even for replacement situations and even in places of high electric/ low gas rates. This requires the effort of putting a timing control device on a tank water heater, something those with basic electrical skills could DIY. Tying this back to topic, new construction skipping air-conditioning could use electric resistance (or heat pump) radiant floor heating during off-peak hours. The floor mass releases heat during on-peak hours of the day and an efficient envelope would keep it in. No combustion inside home necessary and cost effective if done right. A guy is doing it off-grid in Saskatchewan so it might be easy in CA. Here's a link to the controller he built for the PV to electric resistance radiant floor (or battery) interface.

A big yes to all the ground insulation and vapour barriers but ‘cost notwithstanding’ the approach I would favour would be close spaced in-floor hydronic radiant for the lowest water distribution temperature and greatest efficiency, supplemented by hydronic reversible fan coil units that could be used to raise temperatures quickly in heating mode and provide air-conditioning and dehumidification in cooling mode. The response of the slab will be dependant on insulation, thickness of the concrete and depth within the slab at which the piping is installed, among other factors. Piping installed closer to the slab surface will respond faster if thermostat is bumped up; piping sunk deeper into the concrete results in a more stable but slower responding thermal mass. Take your pick. With in-floor radiant you basically heat the first 6-feet from the floor up and who cares about the rest as long as you and your feet are warm. Although ceiling fans would also be useful. With forced air you have to heat the entire volume of the envelope! Radiant is great for working on vehicles in winter as it keeps the floor drier and warmer. The room also recovers faster when garage doors are opened and closed due to the energy stored in the thermal mass of the slab. Also much more comfortable to work on your back underneath a vehicle - that is dry. One integrated energy efficient system with either an air-to-water or geothermal liquid-to-liquid heat pump as an efficient source. The thermal mass of the slab can also be used as a backup during a power failure by just keeping the circulator(s) running continuously with a very small generator to keep the all pipes from freezing for most outages. Your existing electric boiler can be a backup during extreme weather and for compressor lockout or other HP failures. Something else I can tell you from experience, particularly if you plan to own this for some time is that what looks like an astronomical installation cost today will look like an absolute real bargain 15-years from now - if properly designed and installed! IMPO SR