We at our Strata complex need an expert opinion. When going away on holiday in the summer or long periods in the winter too, insurers advise to turn off water supply to house at the main tap. Does this affect the in floor radiant heating system negatively? Should the water supply be left on and the heat left on?

Almost all radiant floor heating systems are "closed", i.e. sealed under pressure like the cooling system in your car. Many have a supply pipe from potable water that is only used to filled and pressurize the heating system.

Some few hydronic heating systems us anti-freeze to assure they will not freeze. most do not.

It is a very good idea to turn of the main water supply and generally a very bad idea to turn the heat off in a living space as many building components may suffer with extreme swings in temperature and/or humidity.

I turn the main water off and the turn the heat down to 50F when gone more than a week.