Does anybody else remember waking up as a child on a cold morning only to pull back the curtains and find a layer of frost on the window on the INSIDE!
Thankfully, for most, those days are long gone but this is a useful reminder to show how far we have come in improving the thermal efficiency of our homes in the past forty years. Central heating, double glazing and deep loft insulation are all now the norm and really contribute to a more comfortable living environment and lower fuel bills.
Modern double glazing often has PVCu frames incorporating sealed glazing units. These units are two panes of glass held apart by beading and often filled with an inert gas to further keep the heat in. They are sealed around the edges and then fitted into the PVCu frames.
Over time, the edge seals can fail and this allows water vapour in the air to enter the gap between the panes. When this water vapour condenses as the air cools, such as at night, then misting up of the windows occurs between the panes. The window also loses much of its thermal efficiency.
This can begin to happen after the units are about 10 years old although it is often possible to replace just the sealed glazed unit and keep the existing PVCu frames.
On one memorable occasion I was surveying a detached bungalow for a RICS Homebuyer report. The bungalow had been empty and unoccupied for some time and was somewhat neglected. From a distance the bottom edge of the PVCu windows just didn’t look right and on closer inspection the gap between the two panes of glass was found to be holding a good six centimetres of water. Repeated water vapour entry and condensation had built up to this level over time. Not quite enough for a goldfish but getting close. Needless to say the sealed units needed replacing. If the water in the gap froze during a cold period then there would be a risk that the windows could break. Even worse than a single glazed window pane with frost on the inside.
Blog provided by Peter Russell (MRICS)