New installation, same problems — the uncomfortable truth about Modern Heating Systems

Modern heating systems promise comfort on autopilot: heat pumps, smart thermostats, weather compensation, zoning, apps. Yet the part nobody puts on the brochure is system complexity-because the more “clever” the install, the more ways it can quietly underperform in a real UK home with draughts, odd pipework, and habits that don’t match the algorithm.

I realised this standing in a newly refurbished hallway, listening to a homeowner describe the same old morning: cold toes, a boiler that “seems to run all the time”, and one bedroom that never quite catches up. The kit was brand new. The problems were vintage.

The uncomfortable truth: new hardware doesn’t fix old behaviour (or old buildings)

A modern system is only as good as the building and the decisions wrapped around it. If your house leaks heat, the best control strategy in the world is still chasing a moving target. If your radiators are undersized, a low-temperature heat pump will feel “weak” even when it’s working exactly as designed.

Then there’s the human bit. People change one setting, forget another, and the system adapts in ways that look like failure: long run times (normal for heat pumps), lower flow temperatures (the whole point), or a schedule that fights your actual routine. You don’t get “set and forget”. You get “set, learn, adjust”.

The cruel irony is that modern heating systems can hide problems better than old ones. A simple on/off boiler made its flaws obvious: either it heated the house or it didn’t. With smart controls and modulation, you can get almost warm, most of the time, while your bills and frustration rise in tandem.

Where things go wrong: the three layers people underestimate

Think of it like a stack. If the lower layers are shaky, the fancy layer on top just amplifies the wobble.

1) Design reality (heat loss, emitters, pipework)

A proper heat loss calculation isn’t paperwork; it’s the map. Without it, installers guess radiator sizes, flow temperatures, and target outputs, then “tune” later with your comfort as the test bench.

Common design mismatches look boring on paper and brutal in January:

• Heat pump sized for an average day, not a cold snap, with no clear strategy for peak demand
  
• Radiators sized for high-temperature boiler water, then asked to perform at 35–45°C
  
• Long microbore runs or restrictive valves that throttle flow and create cold spots
  
• Hot water cylinder recovery that’s slow because coil size doesn’t match the heat source

If you’re swapping a boiler for a heat pump, low-temperature heat is the headline change. That one shift makes the rest non-negotiable: emitters, insulation, and flow rates suddenly matter.

2) Controls logic (smart isn’t the same as simple)

Controls are where system complexity becomes personal. A weather-compensated system wants to run gently for longer. A homeowner wants quick bursts of heat before the school run. Both are reasonable. They’re just not the same strategy.

The traps are predictable:

• Too many “brains”: app schedules + thermostat schedules + boiler/heat pump control schedules
  
• Zoning that looks efficient but starves the system of flow (especially with heat pumps)
  
• Setbacks that are too deep, so the system spends hours recovering rather than cruising
  
• Conflicting sensors: a sunny living room dictates the whole house while bedrooms freeze

If you’ve ever said, “It’s warm in here but cold everywhere else,” you’ve met the politics of sensors.

3) Commissioning and handover (the missing hour that costs you a winter)

Most performance issues aren’t dramatic faults. They’re defaults that never got tailored: flow temperature left too high “to be safe”, balancing skipped because it’s fiddly, or hot water priority set in a way that steals heat from rooms at the worst time.

A proper handover should leave you with three things: a clear control strategy, a simple explanation you can repeat, and a baseline setup that fits your home. What people often get is an app login and a hope.

“The install isn’t finished when the system turns on,” a commissioning engineer once told me. “It’s finished when it turns on predictably.”

Fixes you can steal this weekend (without becoming an engineer)

You don’t need to re-plumb the house to reduce friction. You need to remove conflicts and make the system’s intent obvious.

Start with a reset that’s more boring than clever:

• Pick one place to control scheduling (thermostat or app or controller) and disable the rest
  
• Set a realistic comfort target and leave it for a week; stop “chasing” with constant tweaks
  
• If you have a heat pump, avoid deep night setbacks; aim for a small drop, not a crash
  
• Check TRVs: open the ones in key rooms so the system has somewhere to dump heat consistently
  
• Identify the cold room and treat it as a diagnostic: radiator size, air in the system, balancing, or door undercuts

Then do the low-drama checks that are embarrassingly common:

• Bleed radiators (if you’re on a wet system) and check pressure afterwards
  
• Make sure the thermostat isn’t near a kitchen, sunny window, or a radiator
  
• If you have zoning, confirm each zone actually calls for heat when it should
  
• Note run times rather than panic: long, steady operation can be normal and efficient

Soyons honnêtes: nobody reads the manual cover to cover. So write your own “house rules” on a sticky note: target temperature, schedule, and what you don’t touch.

The simplest metric that tells you if the system is healthy

Forget the app graphs for a moment. Ask two questions over three cold days:

1. Do rooms reach a stable, comfortable temperature without heroic intervention?
   
2. Is the system predictable-same weather, same outcome?

If the answer is no, don’t start by blaming the brand. The usual culprits are configuration and hydraulics: balancing, flow temperature, zoning conflicts, or an emitter mismatch. These are solvable, but they need a method, not more settings.

A small, repeatable improvement beats a perfect setup you abandon. Modern heating systems reward consistency, not constant tinkering.

Point clé	Ce que ça change	Pourquoi ça compte
Reduce control conflicts	One schedule, one “brain”	Stops the system fighting itself
Prioritise low-temp comfort	Steady heat, fewer spikes	Better efficiency and fewer cold rooms
Commissioning matters	Correct flow temps + balancing	Most “faults” are setup, not hardware

FAQ:

• Why does my new system run for hours? Many modern heating systems (especially heat pumps) are designed to run steadily at lower temperatures. Long run time isn’t automatically bad; poor comfort and unpredictability are the red flags.
• Should I turn TRVs down in unused rooms to save money? Sometimes, but be careful. Closing too many radiators can reduce flow and make heat pumps and modulating boilers behave badly. Keep a few key emitters open and avoid extreme shut-downs.
• Is a smart thermostat worth it if my house is draughty? It can help with scheduling and consistency, but it won’t fix heat loss. Insulation, draught-proofing, and correct radiator sizing usually deliver bigger comfort gains.
• What’s the biggest sign of a commissioning problem? A house that never feels evenly warm: one room roasting, another cold, frequent cycling, or constant “tweaking” to get through the day.
• Do I need weather compensation? It’s often beneficial, particularly with heat pumps. The key is setup: correct curve, sensible setbacks, and controls that aren’t being overridden by competing schedules.