JohnMo

Reply may be a little late, but could help others. Are you trying to design around the slip or the durisol? When you are doing the lintels with durisol the blocks are on the end, so 500mm high and 250mm wide. The blocks either side of the window/door opening are modified to take the rebar. The window or door heights can be easily made to suit the slips, with too much additional work. The door opening, by the white box is 2100mm high, the open under the flattish roof, lined up with the blocks at 2000mm, both opening require blocks to be modified.

I chose an Atag A325ECX, it can take preheated water which increases the flow rate, have a thermal store upstream, cold water passes through the stores DHW Coil before going to combi. Store used as a buffer for UFH and has solar PV connected to immersion. So always sits at about 40 degrees. You can go open therm if you want, but have just removed and gone simple route, basic thermostats but with self balancing actuators on the UFH manifold and run UFH 24/7 at a low temp using a mixer and pump after the store.

It may be a bit late, but just commissioned a system similar to what you are looking at, here is what I have, after a few changes. Atag combi boiler, Telford thermal store (acting as a buffer with benefits) with boiler heating coil, DHW heating coil, mixing valve at outlet. Thermostat (middle of tank) set at 45 degrees, to reduce heat loss. UFH running at 30 degrees Solar PV Hook up, cold water to DHW coil, this passes through TS, and into combi, if it is hot or cold, the Atag boiler is designed to take pre heated water, so boiler doesn't care, the boiler only puts the energy it needs to the correct outlet temp. Upside, if preheated, you get great hot water flow. In the summer solar PV should do a lot of preheat. Have a secondary circuit, pump with simple timer at the out DHW outlet, so it can pick up hot water from TS coil or pass through the combi. Boiler was short cycling connected direct to UFH, so the UFH manifold now has mixer valve and pump added, this is connected direct to thermal store. Boiler connected direct to TS heating coil, boiler temp set at 50 degree. Advantages, boiler is always in condensing mode. Simple hook up, low standing losses as the tank is no hotter than 45 to 50 degrees.

That's good to know, we should get our first real prices this week.

Hi all Planning a new build in sunny Scotland, semi passivhaus, just wait for the warrant to be approved. There bed bungalow facing south west looking over a loch. House spec, floor, walls and roof U value of 0.1. Double glazed U value 1.2. UFH throughout. 3.2 kW solar PV, with immersion diverting. Thermal store heated by PV only to provide preheated water to Atag Combi boiler with full weather compensation. MVHR. Air tightness looking for around 1 m3/m2. Did the maths looking at payback for triple glazing and got pay back periods of around 40 years. Due to the low heat demand.