A relatively long set of bullets to allow me to collect my thoughts, mainly for my architect, but thought I would run by here to get some feedback. I hope there is enough context and questions. Sorry if I got anything major wrong I'm a noob at this...
- Current setup
- 5 bedroom, 4 bathroom, 3000 sq ft, semi-detached, Victorian 1890’s build
- Family of four, kids 10 and 7, will be busy times for showers in the morning before school / work and evenings before bed
- Heating: ~20 radiators, about 15 recently replaced on upper floors, attempted to oversize for T40-ish
- Current system: 37 kW system boiler, 250 litre unvented cylinder located in kitchen
- most external walls are already insulated (1 inch ish polystyrene), we will put in new double glazed windows everywhere, and I have been adding insulation to the loft with the goal to get 200mm
- Planned works / reason for change
- We are doing a side return extension which will open up the kitchen and force us to move the boiler & cylinder
- Adding underfloor heating to kitchen (about 50 sq m) and currently unheated basement (about 40 sq m)
- Goals
- Balanced cost to install / cost to run – economics need to make sense
- Reduce energy usage
- Future proof
- Re-use where possible, e.g. existing cylinder
- Options considered
- Heat pump – was excited about this but really could not find a way to make the economics work
- Electric boiler – currently on single phase, and even if we convert to three phase still not enough output, as I understand a ceiling of 100% efficiency would be v expensive at UK prices compared to gas
- Move to combi – feels like a step back
- Move to combi storage – I like the looks of the Viessman 111 or 222, but again seems like a step back
- What I’m thinking
- Re-use existing cylinder (but it’s giant, perhaps oversized??) but if no reason to change we will keep
- Replace boiler with Viessmann Vitodens 200W – seems like a good solution for tech, weather compensation, modulation, efficiency
- Move both to basement if the flue works, else keep the boiler in the kitchen and move the cylinder to basement
- Leverage all the tech in ‘advanced’ weather compensation, no room controls
- Hot water priority
- Two or three zones with different heating curves: 1) upper floor rads, 2) kitchen UFH, 3) basement UFH
- After doing a bunch of research I came across this excellent video from Urban Plumbers which seems to describe almost exactly what I was thinking:
- Questions
- What size boiler do I need – all the boiler companies are telling me the 32kW which I fear could be overkill, and also in this boiler I think would not modulate as low?
- Are there any other boilers other than the 200W I should consider?
- Should I split zones for kitchen UFH and basement UFH? Kitchen will be used many hours a day, and basement much less.
- Any downside to only using weather compensation?
- Any recommendations on who could do this work for me, I’m in London – SE14
- What else should I think of?
