Condensation Season: When “Steamy” Windows Signal Something More
As the weather turns colder and we spend more time indoors, many homeowners start to notice an unwelcome guest on their windows and doors: condensation. A little misting on the glass or frames first thing in the morning might seem harmless, but in some cases it can be an early warning sign of deeper issues with the window or its installation.
At this time of year, RISA frequently sees an increase in inspection requests involving condensation. Understanding what type of condensation you’re seeing is the first step to working out whether you have a problem – and if so, what to do about it.
Not All Condensation Is Bad News
Condensation is simply moisture in the air turning back into water when it meets a cooler surface. Modern homes are often better insulated and more airtight than ever, which changes how and where moisture appears.
One of the most misunderstood forms is external condensation on modern insulating glass units (IGUs) – the mist that forms on the outside face of the glass.
Counter-intuitive as it sounds, this is usually a sign of a highly efficient unit, not a defect. Better insulated glass keeps more heat inside the property, so the outer pane can remain cooler than the surrounding air. Under the right conditions of temperature and humidity, that outer pane becomes the cold surface where moisture settles.
In most cases, this type of condensation is intermittent, disappears as the day warms up, and is not something that can or should be “fixed”.
When Condensation Signals a Problem
Condensation on the room-side (internal) face of your windows is a different story. This can be caused by:
- Occupant behaviour and environmental conditions – high moisture levels from cooking, bathing, drying clothes indoors, or inadequate ventilation will all increase internal condensation, even on well-performing windows.
- Windows and doors that are not performing as they should – design, specification or installation issues can create cold spots and encourage condensation and mould.
From a technical perspective, the most common defects we see associated with problematic condensation include:
1. Under-specification of glazing
If the glass in a window or door set has been under-specified for its location or exposure, the internal glass surface may be significantly cooler than it should be.
For example, failing to use an appropriate low-emissivity coating, warm edge spacer, or suitable IGU make-up can result in poor thermal performance at the glass edge, leading to regular condensation bands around the perimeter of the unit. Over time this can damage finishes and contribute to mould growth on surrounding materials.
2. Incorrect positioning and installation of frames
Even the best glass can be let down by poor frame design or installation. RISA inspectors often encounter issues such as:
- Frames installed too close to cold structural elements
- Inadequate or incorrectly positioned thermal breaks in aluminium frames
- Poor interface detailing between frame and surrounding construction
- Gaps, voids or inappropriate materials in the cavity around the frame
These issues can create cold bridging – pathways where heat escapes and cold is conducted into the building fabric. The internal surface temperature around the frame drops, and condensation forms preferentially at those points. In aluminium systems, where conductivity is naturally higher, incorrect positioning or lack of effective thermal breaks can make the problem particularly acute.
Why a Professional Inspection Matters
Because condensation has multiple potential causes – from lifestyle and ventilation, through to glazing specification and frame installation – it’s not always obvious what’s to blame in any given property.
This is where an independent, technical inspection makes a real difference.
A RISA expert inspection will:
- Review the design, specification and positioning of the glazing and frames
- Assess installation quality and look for evidence of cold bridging or poor detailing
- Consider the property’s overall condition, ventilation strategy and moisture sources
- Distinguish between issues that are the homeowner’s responsibility (such as ventilation and moisture management) and those that may lie with the product supplier or installer
Following the inspection, RISA provides a clear, evidence-based report setting out:
- The likely cause or causes of the condensation
- Whether the glazing and installation appear compliant and fit for purpose
- Practical recommendations to improve matters – which may range from changes to ventilation and heating patterns, through to remedial work on frames, glass or installation details where appropriate.
Concerned About Condensation?
If you are seeing persistent condensation on the inside of your windows, staining, mould growth around frames, or you’re simply unsure whether what you’re seeing is normal, it is worth getting a professional opinion.
RISA’s independent inspectors specialise in fenestration performance and installation standards. We can help you understand whether your condensation issues are an inevitable seasonal occurrence, a symptom of environmental conditions in the home, or a sign that your windows and doors are not performing as they should – and what can realistically be done to improve the situation.
If you’d like to know more about RISA inspections or arrange a visit, please get in touch with our team.