Many questions in 1!

[Col2021]

Doing a renovation/extension. Wet UFH in extension (living/dining/kitchen/utility). Electric ufh in bathroom and ensuite (to avoid running lots of pipe to there). Mains gas heating, plan at the moment is a new gas combi boiler. Total floor area 120m2, half is the extension. Other half is old stone cottage which is getting insulated. 2 bedrooms, office and bathrooms are in that end. As the ensuite will be c20m away from the boiler should we just go for electric showers in there and the bathroom? What brand would be best, I can't abide piddly showers so would need to give good pressure.

Then onto the source of heating! As I said plan at the moment is mains gas boiler. But what are the REAL economics of ASHP? This is in Perthshire. We would have south facing roofs for solar but wife doesn't like the look of panels, so they are out (for now).

Whats the general consensus? 

[JohnMo]

Our boiler to ensuite is around 18m with a combi, a little waiting for the hot to arrive, but by the time you have you clothes off, towel where you want it etc, the hot water is there.  Not much of an issue.  Hot water cylinder would be quicker though.

 

Would not bother with an electric shower.

 

ASHP, can do cooling if you need it, gas boiler cannot.

 

Heat pump economics £2+3k will get an ASHP, if you shop around.  UFH is same for gas boiler or ASHP.  The other parts with radiators, good chance they will need to increase in size, if micro-bore, this will need to be replaced, so this is a cost adder, a cylinder is required for DHW, with a heat pump coil.  You can get a grant, but there is a good chance you can do it way cheaper without it, if your hands on.

 

Energy wise, a well set up system will have CoP of 3 to 4, (1 unit of electric in 3 to 4 units of heat out).  A gas boiler will have a CoP of 0.8, 1 unit of gas in 0.8 units out.  You just need to look at the cost of gas/ electric.

 

There are plenty of poorly implemented heat pumps.  

 

Insulation is your friend, so is airtightness and good ventilation with heat recovery.

[SteamyTea]

17 hours ago, Col2021 said:

I can't abide piddly showers so would need to give good pressure.

Not just pressure, flow is important.

If your 'water heating device' cannot deliver enough power you have to reduce the flow rate, regardless of the water pressure.

One way around this is to use a store of water that is heated in advance.  Then you can have a smaller device heating the water that can be delivered to the shower at just about any rate you like.