Advice for homeowners


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FENSA Advisor

This is Harry.

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Harry works for a FENSA Approved installation company. He's on a mission to help professionalise installers and protect homeowners across the UK, so he started this advice column.

Condensation advice

Many of us may find we have condensation in the house, at one time or another. We may find that in the winter, some rooms are dry while others have condensation on the windows. Well this post is here to give you some advice on combating that condensation problem.


The problem


Modern life means we now live in more comfort, we have rooms that keep us nice and warm and we have really changed the way in which we heat and keep heat in our homes. No longer do we have traditional open fires, nor do we have rather high ceilings. We now use sophisticated heating systems, we have loft insulation and lower ceilings and nice fitted carpets. All of which make our homes more cosy, but more prone to condensation. Why, you may be asking? Well it's simple; water vapour produced by normal living activities simply has nowhere to escape.


So how do you reduce condensation and the damage it can do to paintwork, curtains and wall coverings without sacrificing the benefits of modern day comforts?


The factors


There are 3 main factors governing condensation in our homes, these are:


  • Water vapour content
  • Inside room temperature
  • Outside temperature


Water vapour is produced by things like washing up, cooking, taking a shower etc. but can be controlled to some extent with the use of extractor fans and ventilation.


The inside room temperature can be controlled by replacing single glazing with double glazing. This maintains a higher surface temperature of the glass on the room side, which enables it to hold more water vapour without condensing. It also keeps more heat in your home, so can help reduce those nasty heating bills&


You guessed it though, the outside temperature cannot be controlled, if it could, Im sure many of us would opt for far longer and warmers summers!


How to reduce condensation


There are a number of ways to help reduce condensation for each area in which condensation is appearing. Some of these tips you may do yourself, or some may require a professional window installer. Find a FENSA Approved Installer.


When formed on the room side surface of the glass


  • Provide natural ventilation, best through an opening / vent in the window or ventilating unit
  • Ensure wall vents are fitted and clear (if you dont have an open fire or existing open flu)
  • Open a window in each room to allow the air to change inside your home
  • If using gas or oil heaters, ensure ventilation of the room
  • Ventilate hoods above cookers to outside air if you can
  • Draught proof internal doors and keep them closed.
  • When formed on the cavity side surface of the outer glass
  • Make sure seals are as close to airtight as possible
  • Drill breather holes through the primary frame to connect the air cavity to the drier air outside the home


When formed in the cavity when the sun shines


You will probably want to get a professional to undertake this work for you.


  • Remove the secondary glass pane
  • Discard and remove any desiccant
  • Drill holes to connect the cavity to the outside drier air
  • Dry out the frame area.
  • Seal up any holes or cracks with compound or wood filler
  • Seal completely all wooden surfaces in the cavity with the proprietary wood sealer
  • Replace the secondary pane, taking care to make the seal and all joints as near airtight as possible


To sum up


Condensation is a ventilation problem. Though double glazing can help reduce condensation by acting as a heat barrier, condensation is often caused by the need for air circulation. Modern day living and efficient heat retention means we often find our home has many moisture traps. The best cure is therefore controlled ventilation.


If you feel you don't have sufficient ventilation in your home contact a FENSA registered window fitter and seek their advice.

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What to check before appointing an installer

Check that you use a FENSA Approved Installer but also check the following:

  • Ask family and friends who have used installers about their satisfaction and whether they got a FENSA certificate.
  • Check the installer's references by talking to their previous customers.
  • Get at least three quotes and check you are being quoted like for like.
  • Cheapest is not always best and good contractors are always in demand.
  • Get quotes, timeframes and the fact that you will get a FENSA certificate all in writing. A proper written contract with an agreed completion date will help prevent confusion later on
  • Check the warranty on the installer's work and ensure they have enough insurance to cover their warranty. Domestic glazing installers that are registered with a competent person scheme like FENSA are legally obliged to provide warranty insurance to cover your installation should the company cease to trade within the life of the warranty.
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