I think someone needs to make the point that you don't need a hi-tech heating system costing over €20k and costing €1500 a year at present prices. It seems people spec their houses by selecting a massively oversized heating system. Do you really need 3000 square foot, wouldn't you be better build 2,500 square feet but build it to an appropriate standard.
A properly designed and built house will need a tiny heating system. Electric underfloor in wet rooms and kitchen would be more than sufficient.
Good solar orientation and clever use of daylight along with continuous insulation with no cold bridges and Heat recovery Ventilation with a small post heater is the only option. Building anything else doesn't make sense especially with projected energy increases of 7% per annum.
Instead of getting an Engineer or Surveyor supplied stock house plans, get your building designed to suit your site and your lifestyle and one that is future proofed. I despair when I see the standard of design and construction that people are prepared to accept in this country. We pay above the odds for concrete buildings with plastic insulation or shoddy timber inner leaf's, the design is focused on providing an impressive elevation to the road but doesn't address the path of the sun or the views.
Then we install a huge heating system which goes cold after 2 hours. For 5%-8% extra you can have a Passive house, with light, comfort, natural materials and a responsive heating system for when you need it. A Passive house with no heating will maintain 16 degrees in winter in Ireland.