Whole‑House Renovation: Need Real‑World Advice on ASHP + Fan Coils + MVHR Integration

[NetTechie]

Hi all,

I’m in the middle of a full‑scale renovation of a very tired property — original 40‑year‑old fan boiler, vented cylinder, single‑glazed metal windows, the lot. The house is being stripped back to brick with new floors, ceilings, EWI, cavity insulation, new roof, the works.

I’ve been doing the rounds at the homebuilding/renovation shows, but I’m really struggling to find installers who actually understand integrated systems. I’m an engineer, so I like to get into the detail — but the moment I mention fan coil units, I get blank stares or “we’ll have to ask someone else”. Not reassuring.

My end goal for the refurbished house:

• ~16 kW reversible ASHP for heating and cooling - with UFH throughout + towel rads in bathrooms
• Fan coils for bedrooms, large open‑plan areas and south‑facing rooms
• MVHR with heating/cooling module (going with Zehnder Q600 + CW12, designed by Paul; armaflex radial ducting planned)
• DHW storage — Mixergy looks promising, but installers keep telling me I won’t see any benefit for the outlay
• ~7 kW solar + battery storage

Where I’m stuck is tying together the ASHP, DHW cylinder, fan coils, solar and batteries into a coherent system.

Heat pump thoughts

The LG Therma V R290 monobloc looks excellent on paper — strong COP, good flow rates — but I cannot find a single installer who actually works with LG. I keep getting pushed toward Samsung, Vaillant or Mitsubishi. Two installers have specified Joule cylinders. I’m personally not keen on Samsung due to reliability and integration quirks.

What I’d really appreciate advice on:

1. LG ASHP installers - Has anyone found a company that actually installs LG heat pumps in the UK?
2. Real‑world views on the LG Therma V R290 - Specs look great, but I’d love to hear from anyone who has one running.
3. Fan coil units - This is the big one for me. I don’t want split AC with another condenser outside and messy wall units — I want everything integrated off the ASHP with concealed units in the ceilings / walls. - Anyone used Megawave Energy or other brands? How well do fan coils actually cool during those 30–35°C heatwaves?
4. DHW cylinder choices - Is Mixergy X worth it in a heat‑pump‑led system, or should I be looking at something like Joule?
5. Solar + battery recommendations - I’m being quoted for panels I’ve never heard of at 5× their retail cost. Most installers push Fox batteries — any real‑world experiences?

If anyone has gone down a similar route — integrated ASHP + fan coils + MVHR + solar — I’d really value your insights. I’m trying to design a system that actually works as a whole rather than bolting together whatever each installer happens to sell. Oh and to throw so more complexity, control is important, I had my home automation company years ago, so can design this but the kit needs to integrate into HomeAssistant and Control4, Heatmiser is easy enough for the CH, DHW and FC's but more invested in the solar, battery / energy side of things. And how do I still get get hot water in summer when I'm running the ASHP in cooling mode?

Thanks in advance.

 

[drives]

Can’t advise on all of the above but if it helps….

Why the LG in particular? SCOP figures would be largely the same Id expect for other units.

Is 16kW required- that is very high heat loss if that is what has been specified.

With your last question surely the ashp would simply prioritise DHW so when scheduled it would just stop heating (or cooling) and reheat the tank.

I’d probably steer you towards the renewable heating hub forum with is a bit more specialised for ashp queries. We have a midea which I’ve integrated with home assistant. Works well. There’s some very knowledgeable and techy people on the above forum who have helped me out with our system.

 

[StephenStephen]

You might find this forum useful: https://www.speakev.com/forums/power/