Originally Posted by macliam

Is this a permanent residence? Heat sources that take time to have an effect may be more efficient, but less comfortable in a property left empty for any time.

My house in the Alentejo is Taipa, naturally warm in winter, cool in Summer - an older extension is like a fridge in winter, but a new extension (to the current insulation standards, double block and foam) is even better than the Taipa. It's hard to know how much extra heating/cooling you'll need after that. However, if retro-fitting into an existing building, it may not be easy to reach that level of insulation.

If pouring a floor, add the tube infrastructure..... the cost is minimal for the flexibility offered - but air-to-air may be your best solution overall.

A woodburner or back-burner fire is a possibility - it can quickly heat a confined space and water heating or heat recovery is an option. This means you need to add in a fireplace/chimney - a good focal point even if you don't use it. Pellets are popular, but they are a manufactured fuel, so the current low price can change (like oil did). If going for radiators, pay for good aluminium ones for best heat transfer... especially with lower water temperatures.

The solar water heating is a no-brainer, but again there may be an initial lag if the property is unoccupied for any time (panels may need covering to avoid overheat).

I'd say build with the ability to change later - pre-prepare for underfloor, radiators and A/C - running pipes is a lot cheaper at build time! (run extra electricity outlets and build in CAT-5 too) Then get the best level of insulation you can manage (incl, draught prevention) and live the first period without any extra heat source or cooling (electric heating is cheap to buy). After that, you will know what you need for your comfort and can add-in the required sources. Connecting A/C etc. to existing pipework and a power supply is simple.

Originally Posted by wellinever

Modern AC fixed units are very efficient. Always immediate heat . Get minimum A++ hot and cold. Other benefits fan only and dehumidify.
Insulate the floor with min 4cm Floormate or equivalent. If digging out floor, also use Leca Balls in any concrete screed for added insulation.