Hello,
 
	 
 
	I started a project hastily and it has somewhat escalated. The information here has been amazing.
 
	 
 
	We have a 5 bed detached farmhouse (half/half previous extension, half solid 50cm stone walls, half insulated cavity). Very exposed to winds and rain.
 
	 
 
	We made the decision to put ufh downstairs and upstairs, but admittedly I really should have had a proper heat loss done and spent the extra on a heating engineer. Lack of knowledge and poor advice at the time... but here I am.
 
	 
 
	Build up is 70mm hardcore/blinding, DPM, 150mm concrete slab in mesh, 150mm PIR, 16mm ufh pipes at 150mm centres clipped to insulation with 75mm sand/cement dry screed to SR2.
 
	 
 
	Upstairs, removed old floorboards, leveled the joists, extra reinforced those that needed it, noggins etc... 5cm PIR between joists, soundproofing tape, routed floorboard for 16mm pipes at 150mm spacing. Primer, Perimeter 6mm expansion strip tape and then 1 to 3cm flow screed over the top to level, fill in boards.
 
	 
 
	Upstairs is 6 valves for 5 bedroom zones. The bathrooms are on electric ufh mats.
 
	Downstairs is on 7 valves doing 4 zones.
 
	I am likely going to add another 5 valves for 3 zones for an extension in the future.
 
	All runs are below 100m, 16mm at 150 centres. My thought was this way I can reduce flows and wouldn't be left with a cold house (cant insulate internal or externals of the old part of the house).
 
	 
 
	The 3 manifolds have a manual mixing valve and each with its own pump.
 
	Each manifold has a heatmeiser control that I am told connects to actuators that go on the valves. Then each room will have a thermostat that switches the actuators on and off when the rooms hit the set temperatures.
 
	 
 
	I had assumed that my current boiler/cylinder would have been enough to supply the system.
 
	But my builder's plumber says that it is a very old boiler 10+ years and they would recommend an upgrade.
 
	 
 
	Finally to my question and thanks for reading so far:
 
	My heatloss is around 15 to 18kw. I have ruled out ASHP due to only having access to cost/space and single phase electricity.
 
	If I am going to upgrade my heating system, I would like to have weather comp option and hot water priority.
 
	 
 
	I have had lots of mixed messages and designs about this from different plumbers, with huge varying cost.
 
	So here I am asking for option on what people have done with wet underfloor only set ups. Current recommendation has been a heat only system with a low loss header that supplies ufh and the cylinder...
 
	 
 
	In my head I was thinking a 4 pipe system boilder that has inbuilt domestic hotwater priority. 
 
	Some kind of communication centre that means the heatmeisers can call for hotwater at a different temperature to the hot water cylinder.
 
	Do I need a low loss header for the 3 manifolds to connect to and blend from?
 
	 
 
	Have I shot myself in the foot with the kit I already have (manual mixing valves and heatmeiser) to have weather comp? I am happy to invest time tweaking flow rates etc... to get a more stable heatoutput to stop the actuators constantly opening and closing.
 
	 
 
	Sorry if you think this is better suited to the the ufh forum
 
	 
 
	Thanks again