condensation on sash double glazing windows in Glasgow

4 Causes of Condensation Inside Double Glazing Windows

condensation on sash double glazing windows in Glasgow

Having your view outside obstructed by condensation in your double glazing windows in Glasgow is a headache too many homeowners deal with here in Glasgow. That foggy moisture stuck inside the insulated glass unit is always a nuisance and can even cause mould growth. But what’s behind this bothersome condensation materialising inside your double glazing in the first place? In this blog, I’ll break down the typical causes of internal glazing condensation as it relates to our climate here in western Scotland. I’ll provide an overview of double glazed window construction, examine issues like failed seals, high indoor humidity from our rainy weather, and insufficient ventilation that can lead to condensation build-up between the glass panes. By getting to the bottom of what factors trigger that hazy film inside your double glazed windows, you can find solutions to clear it up for good. With the proper fixes and preventative steps recommended in this post, you can keep your outlook clear while avoiding permanent damage to your window units. If persistent condensation between your double panes has been a problem, read on for Glasgow-based expertise on tackling this common issue once and for all. condensation on double glazing windows in Glasgow

If condensation or moisture has collected between your windows, it is likely due to the seal between panes breaking. This allows heat from which you are paying out to escape, effectively leaving money unclaimed by you and being wasted away as lost heat escapes through another route.

Water vapour is produced by all living creatures in your home, such as humans, pets, and guinea pigs, before condensing when coming into contact with cold surfaces such as glass.

1. Humidity in Double Glazing Windows in Glasgow

Due to the attraction between their weight and cold surfaces like glass, condensation tends to happen more frequently at night or early morning when temperatures are lower and air humidity levels are higher. When hot air meets cool surfaces (like windows), moisture in the air may condense into visible water droplets on them. This process often happens more quickly during these low-temperature and high-humidity hours, when temperatures tend to be low but humidity is high enough.

Condensation on the outside of double-glazing windows is normal during the winter months when temperatures drop and air becomes more likely to condense, yet this does not signal a failure with their performance or insulation capabilities; in fact, it indicates their ability to keep heat inside while stopping it from escaping to the outdoors. This shows your windows are providing effective insulation against heat loss from the inside out as well as keeping heat loss under control within your house.

Condensation on the interior of windows can also be caused by high levels of humidity in your home and poor air circulation, particularly where steam or hot pots and pans are often being used. Although this natural phenomenon can easily be wiped away with soapy water, you should try keeping humidity levels as low as possible to minimise condensation issues in your home.

Failure of the spacer placed between your two panes of glass is another common source of condensation inside double glazing systems. The spacer contains desiccant, an absorbent material intended to absorb any moisture entering through air gaps between them; any imperfection in the window seal could see this moisture enter and be soaked up by this highly absorptive material, leading to excess moisture appearing on the inside as condensation or fog on windows, and this problem could have been present for some time before becoming evident when its capacity for absorption was exceeded and could no longer hold any more.

2. External Temperature Change

Condensation can occur at any time of the day or night, though it’s more likely to appear when it is cooler outside and warmer inside. As the air cools and becomes more humid, water vapour condenses on cold surfaces, including your double-glazing windows, which causes water vapour to stick to them and form drops on glass surfaces, leading to visible condensation when temperatures outside are lower and darker.

If this occurs on both panes of glass in an IGU unit, this could be caused by a problem with its “spacer” bar containing desiccant, which soaks up any excess moisture in the “air gap”. Unfortunately, if any imperfection exists in the window seal or it has worn down over time, desiccant can quickly become saturated with moisture and become ineffective at holding back excess humidity, resulting in condensation on windows and visible fogging on them.

Modern double-glazed windows can accomplish their task more efficiently than older versions, but they still need proper ventilation to function effectively. If condensation begins accumulating between panes when installing new double glazing, it could be an indication that they’re not fulfilling their role properly.

Your old windows were likely allowing drafts in and out, as well as hot air being drawn in to warm the glass surface, meaning it was always warmer than indoor temperatures, leading to moisture formation on contact between the colder outdoor air and your window pane. New double glazing eliminates drafts while keeping interior temperatures much warmer, thus decreasing condensation risk significantly.

3. Poor Double Glazing Air Circulation

Reducing condensation inside double-glazed windows may be troubling, but that does not indicate they’re defective. If they were recently installed and are still under guarantee, contact the company that sold and installed them to report any problems as soon as possible.

If your windows are new, air circulation could simply be inadequate, leading to moisture and water vapour condensing on cold surfaces. This phenomenon is particularly prevalent in older houses built before insulation and ventilation systems became popular.

Reduce humidity in your home and prevent condensation by running a dehumidifier, opening windows occasionally, or installing trickle vents in door and window frames, but this is only a temporary solution as it does not address excess moisture in the air.

Temperature differences are another cause of condensation on windows. Heat can escape out through the glass and reach colder surfaces like sills and frames where it condenses, so insulation must be maintained and frames should not touch walls to minimise this problem.

If you have recently undertaken building or renovation work on your property, condensation may form on the inside of window panes due to wet plaster, concrete, or paint that builds up and causes moisture to form in the air. Any such condensation must be eliminated promptly as soon as it appears in order to avoid rot, mould growth, and the eventual degradation of double glazing units.

Condensation may form between the panes of a double-glazed window if its gasket fails to seal properly, usually caused by poor-quality seals or incorrect installation. A leak or failing seal allows warm air into the cavity, leading to the dispersion of moisture through glass into air pockets and condensation forming on its interior surface—something that may be difficult to identify without an infrared camera measuring the thermal performance of the glazing unit.

4. Faulty Seals

Modern double-glazed windows feature two or more panes separated by an air layer that is sealed around their edges, known as an Insulated Glass Unit (IGU). Modern IGUs typically also contain inert gases like argon or krypton that help minimise heat transfer through their window panes.

Fogging or hazing between the glass panes of your double glazing indicates that its seal has failed, typically when air temperatures in your home drop below that of the outer pane and moisture is forced through by changes in humidity or temperature changes into an ‘air gap’ void in an IGU. Desiccant strips inside these units should absorb this moisture to prevent condensation but over time, this desiccant may become saturated, leading to even more moisture entering and fogging.

If your double-glazed windows have experienced significant condensation, it may be wise to contact the company that installed them and discuss replacing their IGUs. They will be able to advise you on the best course of action.

Repairing a double-glazed window that has a broken seal is possible, though not always beneficial in terms of energy costs. A damaged seal means warm air escapes while cold air gets in through gaps, raising energy costs.

Enhance ventilation in your home and reduce condensation on double-glazed windows by using indoor hangers for drying clothing or linen, properly venting tumble dryers, keeping internal doors open, using ceiling fans to circulate air and opening trickle vents when cooking or showering. By doing so, proper ventilation will also ensure excess moisture does not build up in furniture, carpets, and walls, which could be detrimental to both health and property if left to accumulate over time. Use dehumidifiers if necessary to help eliminate excess moisture!

Quick Guide to Double Glazing Windows in Glasgow Condensation: 

Check out this table outlining potential causes + solutions for condensation inside double glazing windows in Glasgow:

Cause Description Solutions
Failed or faulty seals The seals around the window glass panes have deteriorated, allowing moisture infiltration. This is very common in Glasgow’s wet climate. Have a professional assess and replace the damaged seals. Ensure seals are rated for Glasgow weather.
High indoor humidity With Glasgow’s damp climate, excess indoor moisture from cooking, bathing, etc. can condense on windows. Use exhaust fans, avoid drying laundry inside, and use dehumidifiers to reduce indoor moisture.
Inadequate ventilation Lack of fresh air circulation causes moisture buildup. Common in tightly sealed modern flats. Open windows regularly, install ventilation fans, and consider replacing windows that promote airflow.
Temperature differences Warm indoor air meets cold outdoor glass, causing condensation. Worse on poorly insulated windows. Improve window insulation. Open curtains to allow air circulation and a warm glass surface.
Damaged glass Minor cracks or breaks in the window glass disturb the air seal, enabling moisture. Have a professional assess and replace any cracked glass panes.
Window alignment Misaligned window frames cause gaps, allowing moist air to penetrate the glazing. Have a professional realign and seal the windows correctly in the frame.


Condensation building up between your double glazing panes can be incredibly frustrating, but identifying the root causes is the first step toward finding an effective solution. With Glasgow’s damp climate, issues like failed seals, indoor moisture, and inadequate ventilation often lead to bothersome condensation and foggy window views.

The good news is that once you pinpoint the culprit, there are fixes you can put in place to clear up the condensation for good. Whether it’s replacing damaged seals, installing proper ventilation, or making simple adjustments like opening curtains and windows regularly, you can tackle the problem through proper maintenance and preventative measures.

While minor condensation may come and go with changes in weather and seasons, persistent build-up indicates it’s time to take action. Don’t tolerate lacklustre visibility or potential mould growth – address the issue before it can damage your double glazing windows in Glasgow permanently. With some diligent troubleshooting and the solutions outlined here, you can restore crystal clear views and enjoy fog-free glazing once again.

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