Heating, Hot Water & Cooling System Guides
How each type of heating, hot water and cooling system actually works, what suits which home, and what installing or upgrading one involves.
These pages cover the systems themselves rather than the faults: how each one works, the homes it suits, the practical limits, and what changing to it involves.
Combi Boilers: How They Work and Who They Suit
A combi heats water on demand from the mains, so there is no cylinder and no cold water tank in the loft. That makes it the simplest system to live with in a flat or a smaller house, and the one most sensitive to how good your incoming mains supply is.
hotwaterSystem Boilers and Stored Hot Water
A system boiler heats a cylinder rather than heating water on demand. It suits homes where more than one outlet gets used at the same time, and it keeps mains-pressure showers strong because the cylinder is fed from the mains.
heatingRegular (Heat-Only) Boilers in Older Homes
A regular boiler is the traditional open-vented arrangement: a feed and expansion tank in the loft, a cold water storage tank, and a hot water cylinder below. Plenty of period homes still run one, and there are honest reasons to keep the layout rather than force a combi in.
hotwaterUnvented Hot Water Cylinders
An unvented cylinder is fed straight from the mains, so every hot outlet in the house runs at roughly mains pressure. It removes the loft tanks entirely, but it is a pressurised vessel and carries its own regulatory requirements.
hotwaterVented Copper Cylinders and Gravity Hot Water
A vented cylinder is the older copper unit fed from a cold tank in the loft, open to the atmosphere through a vent pipe. It is a forgiving arrangement with genuinely low running risks, and its weakness is pressure rather than safety.
hotwaterThermal Stores: Heat Kept Rather Than Water Stored
A thermal store keeps a body of hot heating water and passes heat to your tap water as it flows through a coil. Because the stored water is never drunk, the store itself sits outside some of the rules that apply to unvented cylinders.
heatingReplacing a Back Boiler Behind a Fire
Back boilers sit in the chimney breast behind a gas fire and were fitted in enormous numbers up to the 1990s. Replacing one is more building work than a straight boiler swap, because the appliance has to come out of the fireplace and the chimney has to be dealt with.
fuelLPG Boiler Systems Off the Gas Grid
Where there is no mains gas, LPG runs a very similar boiler with different burner components, a bulk tank or cylinders outside, and its own regulator and pipework rules. The heating side of the house behaves the same; the supply side does not.
fuelConverting from Oil to Mains Gas
If a gas main has reached your road, moving off oil removes the tank, the deliveries and the sludge problems that come with an ageing oil system. The heating circuit usually stays; the fuel side is rebuilt from scratch.
heatingAir Source Heat Pumps and What They Ask of a House
A heat pump moves heat rather than making it, which is why it can deliver more energy than it consumes. It also runs at much lower flow temperatures than a boiler, so the house has to be able to heat itself with cooler water.
heatingHybrid Systems: Heat Pump Plus Existing Boiler
A hybrid keeps the gas boiler and adds a smaller heat pump, letting the controls choose whichever suits the conditions. It suits homes that cannot economically be brought down to heat-pump flow temperatures across the whole year.
fuelElectric Boilers: Where They Genuinely Fit
An electric boiler has no flue, no gas and very few moving parts, which makes it attractive in flats and in buildings where a flue is impossible. The catch is electrical capacity and the unit cost of electricity against gas.
heatingWet Underfloor Heating Systems
Wet underfloor heating circulates warm water through loops in the floor, giving even heat at a much lower flow temperature than radiators. It rewards good insulation underneath and punishes rushed floor build-ups.
heatingElectric Underfloor Heating in Bathrooms and Kitchens
Electric mats warm a tiled floor quickly and are usually a comfort upgrade rather than a whole-room heat source. In bathrooms they solve the cold-tile problem without disturbing the heating system at all.
heatingRadiator Central Heating Systems
The radiator circuit is the part of a heating system people think about least and complain about most. Balance, sizing and water quality decide whether a house feels evenly warm or has one room nobody sits in.
controlsTwo-Zone Heating for Upstairs and Downstairs
Zoning splits the house so upstairs and downstairs can be heated to different temperatures at different times. In a two-storey home it is one of the few control upgrades that changes how the house actually feels.
controlsS-Plan Systems: Two Motorised Valves
S-Plan uses two separate two-port valves — one for heating, one for hot water — so each service is controlled independently. It is the layout we most often install because faults are easy to isolate.
controlsY-Plan Systems and the Mid-Position Valve
Y-Plan uses one three-port mid-position valve to serve both heating and hot water. It was the standard for decades and is still very common in local homes with a cylinder in the airing cupboard.
controlsSmart Heating Controls That Are Worth Fitting
Smart controls are only as good as the system underneath them. Fitted to a balanced, well-zoned system they genuinely help; fitted to a system with a stuck valve and cold radiators they just give you an app that shows the problem.
controlsWeather Compensation Control
Weather compensation adds an outside sensor and varies the boiler's flow temperature with the weather. On a mild day the system runs cooler, which is exactly the condition in which a condensing boiler is at its most efficient.
controlsLoad Compensation and Modulating Controls
Load compensation varies the boiler output based on how far the room is from its target rather than on the outside temperature. It needs no external sensor, which makes it the easier retrofit of the two compensation methods.
heatingConverting an Open-Vented System to Sealed
Converting removes the feed and expansion tank from the loft and puts the heating circuit under pressure, with an expansion vessel and a filling loop instead. It is usually done alongside a boiler change and it tests every joint in the house.
hotwaterHot Water Recirculation and Long Pipe Runs
In a long or spread-out house the wait for hot water is a pipework problem, not a boiler problem. A recirculation loop keeps hot water moving so it is close to the outlet when you open the tap.
waterShower Pumps on Gravity Systems
A shower pump takes a weak gravity-fed supply and gives it real force. It only works on the right kind of system, and fitting one on the wrong system causes noise, cavitation and short pump life.
waterElectric Showers and Their Supply Requirements
An electric shower heats cold mains water as it passes through, so it works even when the boiler is off. Its performance is fixed by the kilowatt rating and the incoming cold flow, not by your hot water system.
waterMains-Pressure Showers Without a Pump
Mains-pressure showering comes from an unvented cylinder or a strong combi, with both hot and cold arriving at balanced pressure. Where the incoming supply is good, this beats pumping every time.
coolingWall-Mounted Split Air Conditioning
A single split system pairs one indoor wall unit with one outdoor condenser, connected by refrigerant pipework. It is the most common way to cool one room properly, and most modern units heat as well as cool.
coolingMulti-Split Air Conditioning for Several Rooms
A multi-split runs several indoor units from one outdoor condenser. It keeps the outside of the building tidy and suits houses where three or four rooms need cooling but there is only one sensible condenser position.
coolingDucted Air Conditioning and Concealed Units
Ducted systems hide the indoor unit in a loft, ceiling void or cupboard and deliver air through grilles. Nothing hangs on the wall, which is why it suits properties where appearance is the deciding factor.
coolingUsing Air Conditioning for Heating
A reverse-cycle air conditioner is a heat pump. In autumn and spring it can warm a room quickly at good efficiency, which makes it far more than a summer appliance.
waterBathroom Extract Ventilation Done Properly
Most bathroom damp complaints are ventilation problems wearing a disguise. An extract fan that is undersized, poorly ducted or terminated into a loft will produce mould however new the bathroom is.
waterWater Softeners in Hard Water Areas
Hampshire and Surrey supplies are generally hard, which is why kettles fur and shower screens spot. A softener removes hardness minerals by ion exchange and protects heat exchangers, elements and valves.
waterUpgrading a Weak Incoming Water Supply
Where showers are weak and taps starve each other, the fault is often the incoming supply rather than anything inside the house. Old lead or small-bore supply pipes throttle everything downstream.
waterOutside Taps and Garden Water Supplies
An outside tap looks trivial and has real rules behind it: backflow protection, frost protection and correct isolation inside the property. Done properly it lasts decades; done casually it freezes and splits the first hard winter.
fuelGas Supply Pipework and Why Sizing Matters
A boiler can only burn what the pipe delivers. If the gas pipe from the meter is undersized, the appliance drops pressure under load and behaves like it has a fault when the real problem is upstream.
heatingBoiler Flue Systems and Termination Rules
The flue is the part of a boiler installation most often got wrong and most often picked up at a service. Where it terminates, how it is supported and whether it can be inspected all matter legally as well as practically.
heatingCondensate Disposal from Condensing Boilers
Every condensing boiler produces mildly acidic condensate that has to reach a drain. How that short pipe is run decides whether your boiler keeps working through a cold snap or locks out on the first frosty morning.
controlsZoning Strategy for Larger Homes
In a big house a single thermostat in the hall is a blunt instrument. Zoning by use pattern rather than by floor is usually what makes a large property both comfortable and controllable.
heatingHeated Towel Rails and Bathroom Heating
A towel rail has to do two jobs — dry towels in summer and heat the room in winter — and most fail at one of them because output was never calculated for the room.
heatingLow Loss Headers and Hydraulic Separation
A low loss header separates the boiler's own flow requirement from the system's. On larger or heavily zoned systems it stops the boiler and the circuits fighting each other for flow.
hotwaterSolar Thermal Hot Water Alongside a Boiler
Solar thermal panels heat water directly rather than making electricity. Paired with a twin-coil cylinder they can carry a large share of summer hot water, with the boiler topping up when the sun does not deliver.
hotwaterImmersion Heaters as Hot Water Backup
An immersion heater is an electric element inside the cylinder that can heat water with no involvement from the boiler. As a backup it is genuinely valuable; as a primary heat source it is expensive to run.
waterCold Water Storage Tanks in the Loft
A loft tank feeds the cylinder and, in older homes, the bathroom cold taps. It is out of sight for decades, which is exactly why it turns up in water quality complaints and ceiling leaks.