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Heating

Advice on boilers, radiators, central heating systems and keeping your home warm and energy efficient.

Heating

Condensation, the Facts: What is Condensation?

Condensation causes about 70% of damp problems in the UK. In this series, we explore what is condensation, what causes it, and how to avoid it.

As temperatures outside drop and the heating starts to come on, many home-owners will be plagued by a mysterious black mould. Many people panic that the mould is the side-effect of a costly damp problem but the mostly likely cause is condensation, which causes about 70% of damp problems in the UK. In this series, we explore what condensation is, what causes it and how to avoid it.

What causes condensation?

Condensation is the result of moisture in the air turning into water; this happens when warm air hits cold surfaces, or your home is humid. During autumn and winter, particularly during cold mornings and evenings, condensation can be a problem: the warm, heated air in your house hits the cold windows and turns to water.

Aside from the difference between temperatures inside your home and outside, condensation can be caused by everyday activities in the home; showering, cooking, using the tumble dryer without proper ventilation, and drying wet clothes on warm radiators contribute to the build-up of warm, moist air and steam into your home. As soon as this air hits a cooler surface, it will release its moisture, like squeezing a sponge.

The day-to-day condensation-inducing activities, such as cooking and showering, are not usually a problem during the summer months, as the temperature is warmer and the home tends to be better ventilated, with windows and doors left open. However, in the cooler months, these things add up and could result in a condensation problem.

A bit of water may seem harmless, but if left untreated, condensation can lead to black mould which stains clothes, walls and furniture and is potentially damaging to your home and your health, leading to issues such as rashes, congestion and even bronchitis.

Signs of condensation

With regard to condensation, prevention is definitely better than cure. Keep an eye out for the signs of condensation: as soon as you notice water gathering on the inside of your windows, take preventative steps. Even if you are accustomed to water dripping on the inside of your windows on cold winter mornings, this can be the start of a much bigger problem. You may notice damp patches near the windows, or specks of mould beginning to bloom on your curtains, furniture or walls. This is a result of the moist air settling on soft furnishings and interiors, causing a perfect, damp environment in which mould will flourish.

Don’t hide away from the signs of condensation. If you notice any signs of damp or condensation, call a local trusted damp specialist, who will be able to advise you on the cause of your damp or mould and recommend an appropriate and affordable course of action.

Looking for more heating advice?

Find clear, practical answers to common heating questions, helping homeowners understand everyday issues, know what checks they can carry out safely, and when it is best to contact a qualified professional.

  • What is the difference between a combi boiler and a system boiler?

    A combi heats water straight from the mains on demand - no cylinder needed, which makes it compact and ideal for smaller homes or flats. A system boiler works with a hot water cylinder, storing a ready supply that can serve multiple taps or showers at once without the pressure dropping - better for larger homes with more bathrooms. There's also the conventional boiler, which needs both a cylinder and a cold water tank in the loft - common in older properties. A heating engineer can help you figure out which suits your home best.

  • Is an air source heat pump right for my home?

    Heat pumps pull warmth from the outside air (even when it's cold) and use it to heat your home and hot water. They work best in well-insulated homes, ideally with underfloor heating or larger radiators that work well at lower temperatures. In draughty or poorly insulated properties, the benefits are more limited. The Boiler Upgrade Scheme currently offers a grant of up to £7,500 towards installation, so it's worth getting a professional assessment to see whether your home is a good fit before committing.

  • How often should a boiler be serviced?

    Once a year, by a Gas Safe registered engineer. It keeps the boiler running safely, catches small issues before they become expensive, and is usually a condition of the manufacturer's warranty. Some home insurance policies require proof of regular servicing too. If you're not sure when yours was last done, book one before winter - better to find out before you're sitting in a cold house!

  • Why is my radiator cold at the top but warm at the bottom?

    This issue is almost always trapped air. Bleeding the radiator - using a radiator key to release the air - usually sorts it, and it's one of the few heating jobs you can safely do yourself. If bleeding it doesn't work, or if several radiators are having the same problem, it might be a pressure or pump issue. Worth getting a heating engineer in to have a look.

  • What are the signs my boiler needs replacing?

    Keep an eye out for: frequent breakdowns, energy bills going up without using more heat, unusual noises (banging, kettling, or whistling), a flame that's yellow or orange instead of blue, and any visible leaks or rust around the unit. If your boiler is over fifteen years old and ticking any of those boxes, replacing it is usually the more economical choice - modern boilers are significantly more efficient.

  • Is underfloor heating worth it and do I need a professional to install it?

    For a new build or a big renovation, underfloor heating is often a great investment - it heats rooms more evenly than radiators and can be more efficient, especially alongside a heat pump. Retrofitting in an existing home is more of a job, and how worthwhile it is depends on your floor types and how much disruption you're happy to deal with. Either way - wet or electric - it has to be installed by a qualified professional.

  • Why does my boiler keep losing pressure?

    Some pressure drop over time is normal, but if you're topping it up regularly there's usually a cause: a small leak in the system (which isn't always easy to spot), a pressure relief valve that's releasing water, or air in the system after bleeding radiators. Topping it up via the filling loop is fine as a short-term fix, but if you're doing it more than a couple of times a year, it's worth getting an engineer to look into why it keeps happening.

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