Controlling condensation

Most modern homes are warmer and less well ventilated than in the past, creating the perfect conditions for condensation explains John Lannen of L+L.


Today, many of us are fortunate to live in homes that are warm, dry and comfortable. Through a combination of modern building methods and retrospective home improvement schemes, most houses are almost completely sealed by double glazing, draught proofing, loft and cavity wall insulation. This makes for a cosy home in winter, improving our quality of life, but it also means that our house may be less well ventilated than in days gone by. Excessive moisture can lead to problems with condensation and mould that can damage your décor and cause potential health issues for asthma and allergy sufferers.


Internal condensation

The most common place to find condensation is on the inside face of a windows. It’s the result of excess moisture trapped in the house, created by everyday activities such as boiling a kettle, cooking, washing up, drying laundry, bathing, keeping houseplants and even breathing. In the past, this water vapour would have escaped up the chimney or through door jambs, window joints and other outlets. Whilst we can’t stop many of these activities we can take steps to ensure that the moisture content in our homes stays at a comfortable level.


To minimise condensation you need to remove excess moisture from your home by ventilating it. You can achieve this without causing draughts or making it cold by:


• opening a window in each room just a fraction for some part of every day

• draught proofing internal doors and keeping them closed to prevent moisture migrating from one part of the house to another

• retro fitting inexpensive trickle vents to your window frames especially in problem areas such as bathrooms and kitchens

• installing wall vents and/or extractor fans especially in high humidity areas

• slightly increasing the air temperature inside the house

• keeping some form of low level background heating on in cold weather

• ensuring permanent ventilation of all rooms where gas or oil heaters are used

• fixing a hood over your cooker to remove steam when cooking

• situating radiators under windows wherever possible

• positioning heavy curtains 15- 20cm away from windowpanes and ensuring adequate circulation around the fabric top and bottom

• using an air conditioning unit or dehumidifier.


Condensation between sealed units

Sealed double glazing units are made with a spacer bar, glued and sealed to two panes of glass. The spacer itself is filled with desiccant to dry any moisture in the cavity at the time of manufacture. If the unit has been poorly made, the sealant was inadequate or the desiccant of low quality, moist air will be able to penetrate the seal and, under certain conditions, form misting inside the unit. It’s simply a product failure. A blown sealed unit is easy and inexpensive to replace.


External condensation

The evolution of highly efficient double glazed units that incorporate low emissivity glass and argon filled cavities has inadvertently created a third area where condensation can form. On cold, dewy mornings misting may be seen on the outer pane of your windows. It happens because modern sealed units allow hardly any heat to escape so the external pane of glass remains cold and moist air condensates. This means visibility is temporarily impaired first thing but it has no lasting effects. If the mist bothers you it can be removed using a wiper blade but most people leave it to evaporate as the day warms up. We appreciate it’s less than ideal and as an industry we’re working on the issue. In the meantime, try to view it as evidence that your double glazing is energy efficient - performing well to keep you warm and your heating bills low.


As a family company, L+L believes in delivering high quality products and impeccable service at an affordable price. For advice on condensation or any glazing issue please pop into our showroom at Red Lane, Tewkesbury GL20 5BQ, call 01684 295038 to book a free home survey or visit our website.




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