[suresk]

Letting it get too cold could lead to plumbing damage if you parts of your house get below freezing. 15C is probably higher than I'd leave it if it were vacant, but you do want to leave the heat on and a decent buffer to account for temperature variations in other parts of the house.

[inglor_cz]

I discussed the temperature with the guy who oversaw the construction and he told me that, given that the house is still pretty fresh and moist (it was finished in November '22), lower temperatures would mean a risk of mould developing. 15-16 is the sweet spot according to him.

[suresk]

That's a good point - where I live it is pretty dry, but in a more humid area you definitely want air moving around more too.