You will find with that sort of system it is probably better to keep the rooms cool all the time – in other words, don’t turn everything off, let the house get to +30, then turn on all the air conditioning units all at once. One advantage with your system over a central system is that you can cool down rooms one at a time so as to stagger the load when you start with a hot house.

One of the disadvantages is that you can’t force the hot air out as a furnace blower might. You have to cool the air that’s in the room, not push it out and replace with fresh cool air.

And of course greater potential for leaks… but if they are running a glycol mix that should be good to – 40 you shouldn’t have to worry about freezing issues anyway 😉