Hot water system for two showers and space heating to a retrofit?

[Anonymous]

Any thoughts on the best system to install to heat our water: two showers and a small amount of underfloor heating?

We're carrying a Passivhaus/Enerphit retrofit to our 1930s mid-terrace house in Nth West London. It'll be about 110 m2 once we've added a ground floor extension and a loft conversion. There'll be a bathroom on the 1st floor and an en suite on the top floor, both with showers. We're getting water pressure measured but we'll be having a new 32 mm mains connection installed anyway. We don't need supercharged showers but we want to be able to have both showers going at once, preferably without any effect on the other.

What we'd love to do is put in a gas boiler along with a heat accumulator and solar thermal panels (and even a wood burning stove with back boiler) but having put most of our budget into improving the fabric of the budding (in the form of insulation and airtightness) we're thinking more along the lines of just a large combi boiler or a regular condensing boiler and hot water storage.

A large combi boiler is the most attractive to me because it's one piece of kit. But others I've talked to suggest putting in a regular condensing boiler along with hot water storage because a combi won't provide enough pressure. The other suggestion we've had is is to use a combi boiler but to use the normal DHW output of the combi for one shower and split the heating output with zone valves so it goes either to the underfloor heating or a smaller mains pressure hot water storage cylinder upstairs.

What do you think?

[Anonymous]

Thanks Peter.

[Author]

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