Please Note: This Article is 3 years old. This increases the likelihood that some or all of it's content is now outdated.

Condensation and mould:

This time of year, as the temperature drops, both new homes and old homes are susceptible to the formation of condensation and unsightly mould: new homes because they are effectively a sealed box, and old homes because they often lack effective wall insulation.

Internal moisture build-up is a particular problem for landlords because tenants often complain to the landlord when they see black mould, with little understanding of the cause – they blame the building (landlord) when more often than not they are not maintaining a living / moisture balance.

Moisture balance

Moisture is something that’s a part of living in a home, but it needs to be carefully controlled to achieve a balance which maintains comfort and good health.

A proper understanding of what causes moisture build-up and condensation goes a long way to minimising its harmful effects.

It’s almost impossible to elimination all signs of condensation however small, even in a new home. But there are certain things that are complete No Nos when it comes to condensation, and sometimes landlords must be prepared to educate their tenants about this.

There are three main causes of moisture build up inside a home:

  1. From construction / renovation work where plaster and screeds need time to dry out properly.
  2. From leaks and spills, where water enters the fabric of the building from bust pipes, flooding, overflowing baths and showers and leaking washing machines etc
  3. Moisture generated by the occupants from everyday living which can generate large amounts of moisture. The amount will vary depending on lifestyles, household size and time of year.

Points one and two are less common, but point three is prevalent in most homes, so householders need to be informed as to the best way to deal with this.

A New Moisture Guide

A New guide from the UK Centre for Moisture in Buildings (UKCMB), supported by the NHBC Foundation, explains where moisture comes from and identifies actions that can be taken by occupiers to maintain the right moisture balance in a home.

The guide explains why moisture balance is important, how to identify moisture generation and what to do to minimise excess moisture and its harmful effects.

This UKCMB guide highlights good practice to ensure that occupiers achieve a correct moisture balance in the home, including:

  • keeping the home adequately heated in cool or cold weather – a minimum of 18 degrees at all times should be maintained. This is one of the main reasons why tenanted properties often suffer from black mould build-up
  • keeping trickle vents open to create minimal ventilation
  • opening windows when and where excess moisture is generated
  • making sure that extractor fans and cooker hoods are working and used when showering and cooking – the two main sources of moisture generation – extract the moisture at source and it cannot affect the rest of the home
  • avoiding drying clothes on radiators and anywhere else internally, and make sure that tumble dryers have a proper extraction system
  • moist air is warm air, so it rises to the highest points in the property, where most condensation and mould will appear – bedrooms and bathrooms.
  • Keep rooms clutter free to allow air movement within and between rooms.

The guide includes a moisture calculator that enables one to estimate a level of moisture generation and a video from UKCMB: Moisture guidance all for existing homeowners, landlords and tenants.

Main moisture-generating activities in homes

A table compares 4 different types of household and their typical daily activities and shows average moisture amounts generated each year.

A flowchart helps the occupant identify any issues resulting from excess moisture in the home with an easy step-by-step process with guidance.

Richard Smith, Head of Standards, Innovation & Research at NHBC, say:

“This guide from UKCMB highlights the importance of moisture control in homes and of ensuring homeowners have all the knowledge and tools available to them to ensure a healthy home. NHBC Foundation are delighted to support UKCMB in the production of this publication.”

Moisture in new homes: a guide for occupants

Please Note: This Article is 3 years old. This increases the likelihood that some or all of it's content is now outdated.


  1. That really isn’t on and of course should be investigated + fixed by landlord.
    However, tenants should also be using extractor fans in kitchens + bathrooms + OPENING WINDOWS for proper ventilation often, and if course, not drying clothes directly on radiators, all omissions leading directly to mould.
    Also, especially with shower over bath, the wetted walls + silicone sealant around bath should be wiped with paper towels after showers. (I have experience of this!). Landlords should provide the means for such extraction too.

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