Is insulation worth it?

Press, Volume CXV, Issue 33819, 16 April 1975, Page 14

Is insulation worth it?

(By

H. A. TRETHOWEN,

I, an engineer)

| Over the last 10 or 20 l years there has been somei thing of a. controversy over whether the thermal in sulation of houses is worth | while in New Zealand, h Many of the protagonists I on both sides of this argu- ' ment have a profit motive L in the outcome, and this h ordinary citizen may rightly question whether the advice he receives is unprejudiced. Two local bodies (Christ- | church City and Waimairi County) have enacted byI laws which require that I some minimum standard of I insulation must be met in ! all new houses. Other local i bodies are considering I similar action, and the |l Standards Association of

New Zealand is considering changes to its model-build-ing by-law to include the thermal insulation requirements. "None of these bodies has any commerical gain to make over the issue. Two years ago a comprehensive independent study of the thermal insulation of buildings was made by the Building Research Association of New Zealand (8.R.A.N.Z.). its detailed technical repo-t dealt with many factors including for instance, the effect on dampness and mildew in houses, but concentrated on the costs of heating and on when there is a cost advantage in insulation. The report gave one simple rule on the latter question •— that in any New Zealand building which is to be kept at a

(i.e. heaters not necessarily on all this time) for more than about five hours daily during winter, it will pay to insulate. In the colder towns the figure is even less than five hours, as the costs of fuels go up it will drop even further.

comfortable temperature Studies like the B.R.A.N.Z. one are usually based on the supposition that a similar heating standard applies whether or not a house is insulated. It is quite possible that people would simply take advantage of their insulation by heating more rooms for longer, and, if taken too far, this might negate the cost advantage of insulation. It is therefore reassuring to find that the New Zealand Electricity Department (with help from other government departments and many electricity boards) has carried out a comprehensive survey of the actual conditions and electricity consumptiin in houses. In a statement late in 1974 the Minsiter of Electricity announced that eh final outcome of this survey had confirmed that ceiling insulation had achieved savings of about

30 per cent on space heating, in real houses in actual living conditions. This is very much the percentage saving forecast in the B.R.A.N.Z. study for ceiling-only insulation, so presumably the more than 60 per cent saving forecast for all over insulation (walls and floors too) will also be realised. New Zealanders can therefore expect that in the near future all or most new houses will probably be required to be built to standards requiring some stated thermal insulation performance. The reasons will be first that this will, in the over-all sense, save them money on their total heating service, and in the bargain will give a more comfortable house, and second that it will bolster our national energybudget by slowing the growth in oil imports and capital generating equipment.