I’ve a 6kW nominal, ground-source heat pump as the only heat source. This is a well insulated building standing atop the soil of a European country with a tempe

I’ve a 6kW nominal, ground-source heat pump as the only heat source. This is a well insulated building standing atop the soil of a European country with a temperate climate*. It does a great job at +35°C (passively cooling) and just as great at -35°C. During installation we've even made a mistake and it heated the building up to something like +27°C inside during early winter all without breaking a sweat (or my wallet.) The tech is ready. Many attempts to apply it is what’s getting botched. * EDIT: having checked, most of europe falls within temperate – the country is up north.