Energy useage/cost for average 1930s 3 bed semi?

The thing is that the heat capacity of air is a lot lower than water. So you have to blow a lot of air to get the same heating power, and that means noise.

That's mitigated somewhat if you have giant registers that blow a lot of air so the actual air speed and hence noise is low, but a typical wall split unit has a relatively small indoor coil and so a small fan and you need to spin it fairly fast to push the airflow.

That might be bearable for a hot day in summer, but might be less attractive running all winter, especially at night.

Also this airflow is by definition draughty, which is nice and cooling on a hot day but not ideal when you are cold.

Not to say water systems are silent either, but it's possible to hunt down most of the ticking expansion noises and squash them using rubber pipe brackets.

Theo

Yes, my bad. A hybrid system would be air to water.

Cheers

Dave R

The first house I bought had a Johnson-Starley warm air heating system. I can't say that I found it noisy, and I appreciated the way the lounge would be comfortably warm in a few minutes when I got in, rather than wait tens of minutes for radiators to warm a room from cold. There was also a gravity-fed hot water supply for the bath/shower which had no moving parts (other than the water of course!).

The fan was in the kitchen; all the upstairs rooms had a grill in the ceiling where the warm air entered the room. The grills were quite a way from the fan, and weren't noisy.

The grills are normally out-of-the-way at floor level on the ground floor, so it's not difficult to sit where there's little or no draught.

No doubt, but if the system leaks you're into a world of pain which doesn't occur with warm air.