Kylee Joyce, at Stirling School, South Otago, asks :-

How do you prevent frost damaging houses?

Malcolm Cunningham, a physicist at the Building Research Association of New Zealand, Porirua, responded.

In order to prevent frost from damaging your house you must insulate all water pipes, keep the house warm and prevent condensation and ice forming on the inside of windows.

One of the most expensive ways for frost to damage a house is if water freezes in a pipe in the ceiling. In turning to ice, water expands and can rupture the pipe. When the pipe warms up, water flows into the house damaging all fittings. It is not enough to just insulate the pipe itself. If the pipe is in the roof space above the house's insulation and if there is a long cold spell for which the temperature is less than that at which water freezes (zero degrees Celsius) then the pipe will eventually ice up and burst.

The pipe's own insulation helps in this case only in that it slows the cooling process down. So the answer is to not only insulate the pipes but to keep them in warm places, such as underneath the roof insulation.

Another way to prevent such damage is to leave the water flowing slowly in the pipe so that the almost-freezing water in the pipe will be continually replaced by mains water which will generally be a little warmer.

Window glass is a very poor insulator so that on frosty days ice or moisture condenses on the inside of windows. This water accumulates on the window ledge and can rot the woodwork. This problem is solved be installing double glazing for windows. The air-gap between the two panes of glass slows the loss of heat and causes the inner pane of glass to be warmer - too warm to condense moisture out of the indoor air.