Do Blackout Thermal Blinds Cause Window Condensation? Here’s What You Need to Know

Blackout thermal blinds are a brilliant way to improve insulation, block light, and keep rooms comfortable all year round. However, some homeowners notice an increase in condensation on their windows after installing them. So what’s really happening — and should you be concerned?

Why Condensation Happens

Condensation forms when warm, moist indoor air meets a cold surface, such as window glass. This is a normal occurrence in many homes, especially in colder months or in rooms with higher humidity levels.

How Thermal Blackout Blinds Affect Condensation

Thermal blinds are designed to insulate, which means they create a barrier between the warm room and the window. When they fit snugly:

• The glass can become colder because less warm air is circulating against it.
• A small amount of warm, moist air can get trapped behind the blind, forming a pocket of humidity.  When this warm air hits the now-colder window surface, condensation is more likely to appear.

It’s important to note that blackout thermal blinds don’t cause condensation — they simply highlight moisture that already exists in the room.

Common Situations Where Condensation Increases

You might see more moisture if:

• The blinds sit very close to the window frame
• The room has naturally higher humidity (e.g. bedrooms, kitchens, bathrooms)
• Windows are older or single-glazed
• Ventilation is limited or trickle vents are closed

How to Reduce Condensation While Using Blackout Blinds

A few simple adjustments can make a big difference:

• Leave a small gap at the bottom of the blind to allow airflow behind it
• Ensure trickle vents are open, or crack a window slightly for ventilation
• Use a dehumidifier in moisture-prone rooms
• Avoid drying clothes indoors without adequate ventilation
• Consider upgrading to double or triple glazing if your windows are older

The Bottom Line

Blackout thermal blinds offer great energy-saving benefits, but they can change how air circulates around your windows. If there’s existing moisture in a room, that change can make condensation more noticeable. The good news is that with proper ventilation and simple habit changes, most homeowners can keep condensation to a minimum while still enjoying the comfort of thermal blinds. If you have any questions about your blinds or need tailored advice for your home, we’re always here to help, contact us on 01908 502141.