The quality of the air in our homes is currently a hot topic of discussion with a number of recent studies suggesting that controlling air quality in our homes can have many benefits for our health.  Though the purpose of this page is to set out how condensation forms in our homes (in which air quality plays its part), we also illustrate here how safeguarding your home from condensation, if done correctly, can bring other benefits for your health too.

Condensation is an ever-increasing problem in today’s homes.  Modern windows, doors and bricked-up fireplaces dramatically reduce the heat that is lost from our properties, which is a good thing in principle, but they also prevent air that has a high moisture content escaping the home and being replaced by new air.

The moisture content of air is measured in Relative Humidity (RH); this is given as a percentage which indicates to what degree the air is saturated at its current temperature.  The recommended RH value for internal air is 40-50% and maintaining this has a positive effect on both the condition of our homes and our health (the latter is addressed later on this page).

Dew Point Index

It is important to understand that RH is only one value which factors into whether condensation will form in the home.  The dew point temperature of a surface and the temperature of the room it is in must be measured to understand at what point the surface will be affected by condensation.  The dew point is the temperature that a surface must reach in order for condensation to form on it, given the state of the environment that the surface is in.

The dew point is never fixed and will increase or decrease depending on what the RH value of the air near the surface is.  The table on the right illustrates the relationship between RH, the room temperature and the dew point; the dew point temperatures can be seen in the grey section and are provided in Degrees Celsius.



The following basic example should help you to understand how these principles work in practice:

A four walled room is kept at a constant temperature of 23°C by a central heating system.  The room is used frequently and there is no ventilation in the room, which causes the RH of the air in the room to be 65% for extended periods of time.  Two of the walls in the room are internal walls and their normal surface temperatures are each 21°C.  Two of the walls are external walls; one was constructed as part of a recent renovation project and has the benefit of cavity wall insulation whereas the other is an older solid wall with no insulation. 

It has been a cold month and the normal surface temperature of the insulated wall has been 18°C, but the normal temperature of the solid wall has been 15°C and the inhabitants have noticed that this wall appears damp in several places. 

Identifying condensation is rarely a simple process as the traits of condensation can be remarkably similar to other problems such a rising damp and penetrating damp.  As such, we would always recommend that you contact us if such a problem is discovered.  Not only are we experts in diagnosing condensation, we are industry leaders in planning and installing measures which can reduce and resolve condensationproblems in the home.  Please refer to our Alleviating Condensation and Improving Air Quality (link) to find out more.

What our clients say about us

  • "Fast, effective and great price! Had Allerton Damp in to repair my damp course and replace some damp plaster in my living room. Quality service- the surveyor was friendly and explained everything clearly, then the rest of the staff were polite and friendly. Fantastic and clean result, I'd highly recommend them."

    Alex SWakefield
  • "Allerton tradesmen were very helpful and spent time inspecting the problem we had with damp and mould in a few places within one of our rental properties. There was no hard selling of any products and services, and advice was freely given. The work was completed to a very high standard and I am confident to recommend this company and will definitely use them again."

    Russel BBradford
  • "Very professional company, the job was very well executed and done thoroughly with great customer service. Would recommend to anyone!"

    Tony SLeeds
  • "Would thoroughly recommend Allerton Damp Proofing. Our surveyor was incredibly helpful and was able to clearly explain what was causing our kitchen dampness. Their quote was actually the cheapest and the resulting work was fantastic- 6 months on and still no return of the dampness!"

    Anneka TYork

Please note that, as a provider of essential services, we are still open for business, with some restrictions. As a new or existing customer, you can continue to call us to discuss new or existing projects.

Please note that we have had to restrict our work in occupied homes considerably, due to the risk that this might pose to our customers and workforce. However, our work in empty homes and properties continues largely as normal.

If you would like to speak to a member of our team about anything to do with our work during the COVID-19 crisis, please contact us, as normal, using any of the contact details on this site.