Having house renovated and extended; need advice on heating

We'll be soon having our 1931 house renovated and extended. This renovation will include EWI, underfloor heating, solar panels and heat pump. The idea will be to bring the BER up to an A-rating. We currently have a gas-powered combi boiler; so we get our hot water on demand. With this we've got a pump that engages any time a hot water tap is turned on.

With the addition of the heat pump I'm assuming we'll get rid of the combi boiler. I don't know what our best options are for hot water. I really like the on-demand nature of the combi-boiler, although I'm not a fan of the loud pump. In terms of our usage patterns, I have a 5 min shower in the morning and my partner has a significantly longer shower - this could be 20 mins. We then use the on-demand water for washing dishes. We'd also use the hot water for hand-washing but it takes too long that we just use cold water.

So in summary, when i've got a heat pump, what options are available for hot water supply to sinks/showers?

The heat pump will heat the hot water, I'm not sure what the qn is?

You could also have an eddi from the solar, great in summer.

You’ll have a hot water tank installed which the heatpump will heat on a schedule or it can be configured to heat it up any time it drops in temperature a bit, your showers etc will draw from this. You’ll want it pumped but there are very quiet pumps out there, just make sure to ask for that at the planning phase.

For reference our heatpump runs for about 2 hours at 1am to heat hot water at the moment, using 1.2kW so about €0.20 a day. We have a 300L tank although the temperature sensor is over half way up so the whole tank is not being heated. It heats to 50 degrees and we get two 10-12 minute adult showers in the morning then two baths for the kids around 7pm and there is still hot water left at that stage. Modern factory insulated tanks are pretty incredible, you have nothing to worry about once the tank is sized correctly.

Similar system to yourself (and Zenith63). Recently had solar fitted with an Eddi. Have had a heatpump for over a year.
Our heatpump is scheduled to heat the 250ltr tank to 50degrees at 5am (night rate). That gives us enough hot water for the day, including two showers. Now with the Eddie, I have that set to heat the water with excess solar. So the water is getting up to 70 degrees at the moment.
There will be a bit of an adjustment to what you're used to . Initially, the water only coming out of the hot tap at not-scalding (when we only had the heatpump) was a bit of a learning curve. Now it's coming out much hotter due to the Eddie and great sun we've been having.

I highly recommend underfloor, a heatpump,and solar. It really makes the home so much cheaper and more comfortable.

Is it an air-to-water heat pump or air-to-air. The former would be able to heat a hot water cylinder, the latter would not (I believe there is only one specific recently released model capable of doing so). But do you have space for a cylinder, has it been designed into your renovation project?

Zenith63 said:

You’ll have a hot water tank installed which the heatpump will heat on a schedule or it can be configured to heat it up any time it drops in temperature a bit, your showers etc will draw from this. For reference our heatpump runs for about 2 hours at 1am to heat hot water at the moment, using 1.2kW so about €0.20 a day...It heats to 50 degrees and we get two 10-12 minute adult showers in the morning then two baths for the kids around 7pm and there is still hot water left at that stage.

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Thanks Zenith - that's helped to fill in a blank in my knowledge about the capabilities of the heat pump. I was under the impression that the heatpump might only be used for central heating; thinking that it would be heating the water to ~40C for central heating which probably wouldn't be enough for showering.

Can the heatpump heat water for the central heating at the same time as heating water for the tank? Or is it a case that once it's heating water for the tank it won't be supplying water to the central heating?

conor_mc said:

Is it an air-to-water heat pump or air-to-air...But do you have space for a cylinder, has it been designed into your renovation project?

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Although the specific unit hasn't been chosen yet it will almost definitely be air-to-water. The position of the tank hasn't been chosen yet, but now that I know we'll need it I'll be able to accommodate it.

Buddyboy said:

I highly recommend underfloor, a heatpump,and solar. It really makes the home so much cheaper and more comfortable.

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Good to know, thanks!

gdn888 said:

Or is it a case that once it's heating water for the tank it won't be supplying water to the central heating?

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Exactly. It will stop sending hot water to your radiators and send it to the hot water tank at a higher temperature for a couple of hours, then flip back automatically.

Yes with the normal Heat Pump setup, you have to add a hot water cylinder and the heat pump heats it as Zenith outlines.
However there are alternatives. You can forego the hot water cylinder and use point of use heaters for your hot water.
This video does a great job of explaining them
For your hot water taps, I think this is probably the most efficient and cheapest to run option (even versus the higher HP COP or lower Gas cost).
Then for your shower you can use an electric shower (although this will definitely be more expensive to run than HP or Gas).

The advantage of using point of use heaters is you don't need a hot water cylinder (so cheaper install and you get some space back). They can also be paired with Air to Air Heat pumps (so very inexpensive install). And then there are the other benefits listed in the video.