Underfloor Heating & Hot Water
Wet underfloor heating with a mains-pressure cylinder and heat battery — gentle warmth and hot water, stored ready
Warm floors, every wall back, proper showers — and a heating system that runs at the cheap end of the thermostat. Installed and made good by the same team that builds the rooms.
See How It Works
Two drawings. How the system works, and what it does to your money.
*Illustrative guide figures while launch pricing is finalised — your exact numbers follow the free survey.
What We Do
Underfloor heating turns the whole floor into one large, gentle radiator, running at 35–45°C instead of a radiator's 70°C — the perfect partner for a heat pump, and a different kind of comfort in any home. OKPW designs and installs zoned wet systems together with a mains-pressure unvented cylinder and a compact heat battery, so hot water is stored ready and cheap-rate energy is banked for later. Because we build as well as design, floors are lifted, screeded and made good by the same team — not left for a second contractor.
What It Is For — and What It Is Not
Underfloor heating is a comfort and design upgrade: warm floors, every wall back, no visible emitters. It is not an energy-saving product on its own, and we would rather tell you that now than after you have paid for it.
Right for your house if…
- The floors are coming up anyway — an extension, a new screed, a whole-floor renovation. The disruption is the cost, not the pipework.
- You are putting in a heat pump. Low flow temperature is where the efficiency lives: measured UK field data shows 3.50 units of heat per unit of electricity at 35°C flow against 2.38 at 55°C.
- You want the walls back. No radiators means furniture where you want it and glass where you want it.
- The finish is tile, stone or engineered wood. Hard floors conduct; that is the whole point.
- You want proper showers at the same time — a mains-pressure cylinder is the other half of this job.
Not what you want if…
- You are buying it to cut bills on a gas boiler. It saves in the region of £90 a year against a retrofit that realistically runs £7,500 to £23,000. That is a payback measured in centuries.
- You want fast, on-demand control. A screed floor takes two to three hours to respond and as long to cool. Radiators genuinely suit that better.
- The floor is going under thick carpet. Above 2.5 tog for carpet and underlay combined, do not fit it — and under 1.5 tog is what you want on a heat pump.
- Ceiling heights, door thresholds or the staircase cannot take the build-up. Raising a hall floor by 100mm shortens the bottom stair riser by 100mm, and the regulations require a consistent rise through the flight.
- Your mains cannot support an unvented cylinder. Manufacturers typically want around 1.5 bar and 20 litres a minute — well above the 0.7 bar your water company is obliged to supply.
- There is no safe, visible discharge route for the cylinder. Flats above ground floor and internal cupboards end this job before it starts.
- The building is listed. Consent is needed for internal work, and refusals are common over original boards, flagstones and encaustic tiles.
Anyone quoting underfloor heating at 0% VAT as a general rule is wrong. Underfloor heating, cylinders and pipework are not on HMRC's qualifying list. It can be zero-rated as part of a heat pump installation where the heat pump is the principal element — not automatically, and we confirm the treatment for your job rather than promising a rate.
Our Process
Design Survey
We assess your layout, floor build-ups and insulation to design heating and hot water that suit the property.
System Design
Zoned loops, manifold position, cylinder and heat battery sizing — designed for low flow temperatures and quiet, even warmth.
First Fix & Loops
Manifolds, pipe loops and screed or overlay build-ups installed and pressure-tested during first fix.
Cylinder & Heat Battery
The unvented cylinder and heat battery are plumbed in and integrated with your heat source and controls.
Commissioning
Loops balanced, controls configured, and a handover covering zones, schedules and maintenance.
What's Included
- Heat & floor build-up design survey
- Zoned wet underfloor heating
- Manifolds, pipe loops & screed coordination
- Unvented mains-pressure cylinder
- Compact heat battery
- Smart zoned controls
- Integration with heat pump or boiler
- Pressure testing & balancing
- Flooring lifted and made good
- Building regulations sign-off
What You Need to Know Before You Buy
The parts that decide whether this is a good idea in your house.
It is an emitter, not a heat source
Fit underfloor heating, keep an 80°C boiler and change nothing else, and you will see almost nothing on the bill. The saving comes from running the water cooler, which is why it belongs with a heat pump or with a boiler properly set up for low flow temperatures.
Buy it for comfort and wall space
On a gas boiler the honest figure is around £90 a year, about 8%, modelled on 12,000 kWh a year. Against the cost of a retrofit that never pays back. The reasons to do it are the warm floor and the walls you get back — both real, neither financial.
How much height it adds
A full new build-up with insulation is 90–130mm. A low-profile overlay is 15–25mm plus the finish. Anyone quoting no height gain at all is selling you electric mat, which is a different product with very different running costs.
There is an output ceiling
Design for 50–70 W/m² with a real floor covering on it. Be very cautious about underfloor heating as the sole heat source in any room losing more than about 100 W/m² — a big glazed extension or a poorly insulated room may need a radiator as well, and we would rather design that in than have you cold.
Insulation underneath is not optional
Building Regulations require at least 1.25 m²K/W beneath the pipes and cap downward heat loss at 10 W/m². That is roughly 30mm of PIR. Overlaying an uninsulated slab breaches it, and from March 2027 the requirement widens to floors over the ground.
Every loop is one unbroken pipe
No joints buried in the screed, ever, and the manifold stays accessible, drained and powered. The pipe carries an oxygen barrier to a defined limit — without it the damage turns up years later in the boiler, not in the floor.
Electric mat has its place — a small one
A 4m² mat used two hours a day costs around £115 a year to run, which is fine for a bathroom floor. Whole-house electric underfloor heating costs roughly three times what the same heat costs from gas, and about three times a heat pump. We will tell you which one you are being quoted.
The cylinder is a performance upgrade, not an energy one
Mains pressure at every outlet, and hot water running cost goes up slightly — a compliant 200 litre cylinder is capped at about 2.06 kWh a day of standing loss, roughly £76 a year via a heat pump. A heat battery buys you the airing cupboard back rather than a lower bill; sell it to yourself on the space.
Ask for the reheat time in writing
An unvented cylinder is not a combi and it is not unlimited. Two independent safety devices are required beyond the thermostat, factory-fitted and not to be relocated, and the whole thing needs a competent-person certificate.
The rules tighten in March 2027
England's new Approved Document L applies from 24 March 2027, with transitionals to 2028: the 55°C flow temperature rule hardens, underfloor heating must be designed for the resistance of the actual floor covering, and floor insulation scope extends. We design to it now.
Figures correct at 10 August 2026, from Approved Documents G, K, L and P, BS EN 1264, Nesta and the DESNZ heat pump field trial. Prices are market guides, not a quote — yours follows the survey.
Why Choose OKPW
Even, Gentle Warmth
Low flow temperatures make the whole floor the radiator — the perfect partner for an efficient heat pump.
Mains-Pressure Hot Water
A properly sized cylinder means full-pressure showers, with cheap-rate heat banked in the battery for later.
Floors Made Good
We lift and reinstate floors ourselves — one team, no second contractor, no loose ends.
Make Your Home Worth More
A free, no-obligation survey by the people who do the work — covering Putney, Wandsworth, Richmond, Kingston, Streatham and Lewisham.
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