Is damp and humidity the same thing?

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Humidity is the word used to describe the amount of water vapour in air. It is something that can be quite noticeable in the weather. For example, in summer when weather is warmer, you can feel when it is a hot and humid day. People will often describe it as sticky, close, or muggy.

Humidity can also be an issue inside the home, especially if there is poor ventilation and water vapour is not being able to circulate out.

Damp on the other hand, is when surfaces in your property become saturated with water. This can happen for a variety of reasons. These include:

is damp and humidity the same thing
  • moisture penetrating through defects in the building from outside, through areas like the walls and roof.
  • Water rising from the ground below your home. This is known as rising damp
  • And condensation causing damp inside your home.

Damp and humidity are not the same thing. However, humidity does cause internal condensation damp.

When the moisture content in air is high and reaches saturation, it has a dew point temperature. When the moist air meets a surface that is below that dew point temperature, it will condense into liquid water on the surface. This is commonly known as condensation.

A good example of this, that we are all familiar with is condensation on windows.

Windows tend to be colder than other surfaces in your home. As a result, it acts as a dew point and water will form on its surface.

Another common way to see this in action, is to take a cold drink from the fridge. This could be a can, bottle, or a glass of liquid that has been placed in the fridge to chill.

If you place the drink down and leave it for a short while, you will start to see condensation forming on the surface. This is the cold drink acting as a dew point. This condensation will increase, appearing faster in more humid conditions.

How does condensation form when it is humid?

As relative humidity reduces, the dew point temperature also reduces.

This means that if there is less water vapour in the air, surfaces need to be colder for vapour to condense and form liquid water.

It is also worth noting, that temperature effects the maximum water content in air. Warm air can hold more moisture than cold air.

For example, at 30°C water can hold approximately 30g of water per cubic meter. As the temperature drops, so does the maximum water content, before the air reaches its saturation point.

As air temperature drops to 20°C, it can only hold approximately 17g of water per cubic meter. At 10°C, this goes down to roughly 9g.

This is one of the main reason’s condensation on windows is such a big problem during very cold weather.

When it is cold outside, the heating tends to go up in our homes. This is obviously the natural response, its cold, so turning the central heating on will warm up our home and make it more comfortable.

However, this is also a time when more moisture is created in the home and ventilation is poorer. Below are a few reasons humidity rises in these conditions.

  • Windows are left shut due to cold weather. This means moist humid air cannot circulate out and be replaced with fresh air.
  • People tend to leave the house less. As it is cold, people are more likely to spend time in the home, where it is nice and warm. Breathing and perspiration will add to water vapour in the air.
  • Drying clothes outside is usually not possible in cold weather, so this activity is often brought indoors. This produces huge amounts of moisture in the air.
  • Steam doesn’t escape during activities such as showers, baths, and cooking. Again, this is due to windows remaining shut resulting in poor ventilation.

All these activities mean, that relative humidity in your home will be higher. Also, because the weather is so cold outside, surfaces like windows are well below the due point temperature. This results in the ideal situation for condensation to form.

How can you lower humidity to stop condensation damp?

The key to reducing condensation is lowering humidity in your home. As we have mentioned previously, this can be harder to achieve in winter due to poor ventilation. However, there are a few things you can do to try and improve it. These include:

  • Open windows. If it is cold outside, then try just opening them slightly. Most UPVC windows can be opened a small amount, then the handle can be closed. This locks the window in place and allows a small gap for air to circulate, whilst leaving the window secure.
  • If possible, try to avoid drying clothes indoors. If this is not possible, then consider isolating this activity to one room. This room should be shut off from the rest of your home. Also, make sure this area is well ventilated.
  • Consider installing extractor fans in rooms that produce high amounts of moisture. This will usually be your bathroom and kitchen.
  • Use a dehumidifier. This can be an extremely low-cost, effective way of removing moisture in the air. You can read more about how dehumidifiers can reduce damp by clicking here


In summary, damp and humidity are not the same thing. However, they often go hand in hand. When humidity is high, damp caused by condensation is not far away.

The good news is it can easily be reduced by just being mindful of it.

Make a conscious effort to improve the ventilation and air circulation throughout your property.

If you do this, the relative humidity will be much lower. This will result in lower levels of condensation and damp will be far less likely to occur as a result.