Condensation on Windows?

Most of New Zealanders have experienced condensation on their windows. This problem occurs especially in autumn – winter seasons, when the temperatures outside are significantly dropping, and inside heating becomes essential for homes to make people feel comfortable. In this article we will summarize some facts and explain the physical nature of condensation.

WHY CONDENSATION OCCURS

Firstly, it happens when the house heating system is running and there is a significant difference between the inside and outside temperatures. The warmer air is at higher pressure than cold air is, and this causes it to travel out through windows, walls and ceilings. When air collides with cold surfaces such us concrete, glass or aluminium, it causes it to cool down. Once the air temperature has decreased below dew point (the point at which air can no longer hold water molecules) water vapor changes state from gas to liquid. This process is called condensation.

WHAT PROBLEMS CAN CONDENSATION CAUSE

Condensation on windows can lead to various problems. Prolonged and recurrent window sweating may cause formation of mould around the windows and on the walls. Mould, can be an unsettling issue as it can cause health problems such as allergies, asthma, bronchitis and others. Condensation can also affect other house materials, e.g. plasterboard in the walls can experience susceptible moisture damage, joinery parts such as hinges, screws and mitres can corrode and consequently leak.

CONDENSATION ON ALUMINIUM WINDOWS

Metal’s nature is to be a very good thermal conductor, which results in both, heat and cold being transferred easily. When it comes to aluminium window frames, their very low thermal resistance can cause any indoor heat to escape through aluminium frames. Simultaneously, when warm air gets in contact with the cold window frames, the temperature drop results in the release of moisture and condensation.

There is no doubt that double glazed aluminium frames are very popular in New Zealand for improving window efficiency, however homeowners should take into consideration the fact that condensation will still occur on frames and quite often on glass around the frames too, so proper ventilation will need to be provided to prevent this from happening.

WHAT ABOUT TIMBER WINDOWS

Timber has a vary high thermal resistance, so heat loss is reduced remarkably. Old windows however, are often single glazed and condensation can occur on glass pane. It might be not easy or cost effective to try to double glaze old wooden joinery so insert thermally performing windows into existing timber frames is a great solution.

Find out more about Vtite uPVC insert windows.

Insert Windows

THERMALLY BROKEN FRAMES

Generally speaking, yes thermal break, a polyamide strip that divides aluminium frame into two pieces supposed to create a thermal barrier to reduce the heat transfer, in fact it does a very good job, however there is the trick.

Unfortunately, the most common installation detail for windows and doors in New Zealand is with the window frames exposed towards outside, which places thermal break into wrong position. The drawing below illustrates how the heat can still easily travel outside and cause condensation to occur.