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Design Review: Volume 4, Issue 3 (June-July 1952)

Technical — Insulation in the Home

Technical
Insulation in the Home

In your last issue by limited correspondence I drew attention to the importance of insulation when considering the question of heating the home in winter. The use of insulating materials in original design is also necessary to ensure the maintenance of a cool summer atmosphere in temperate zones.

None the less, when considering the important and very much neglected question of equitable and pleasant temperature in the home in both summer and winter a number of other considerations must be borne in mind. These considerations are connected with original design—i.e., the orientation of the dwelling, its roof construction, the size of windows and construction of floors. These factors will not be investigated in this short note, as it is assumed that proper attention would be paid to these matters in construction. My object is to point the way to a summer-winter compromise within the home; to stabilise and so avoid extremities of both cold and heat; to conserve warmth produced during winter months, and to prevent its early escape and waste by lining ceilings and walls with, as it were, a skin of material designed to insulate.

Briefly the crux of home insulation is to prevent the inner linings of walls and ceilings becoming cold and winter and hot in summer. Hence the necessity for insulation between outer and inner walls. The effect of wall temperature versus air temperature in a room is amply demonstrated by reversing conditions thus:

The majority of building boards have a certain efficiency in thermal insulation, but the materials which I describe in this article are produced specifically for the job of insulation, and their satisfaction in use should therefore be much higher. Heating within a dwelling is generally intermittent. It is therefore as important to line heated
Wall TempAir Temp
70°56°Very comfortable.
56°70°Uncomfortable.
Heat loss by air to walls and body adjusting itself to lower air temperature.
rooms with lightweight sheets (fibre board, plaster board, etc.) to facilitate ‘warming-up’ as it is to provide rock wool for thermal insulation. Ceiling insulation is effective in heated rooms, and one or two inches of mineral wool laid on ceilings is adequate provision. The value of insulating walls varies with the conditions. If windows are relatively large the effect of insulating the remaining wall is likely to be small. Insulation of timber frame walls may be achieved by placing mineral wool in the cavity in the form of blanket batts or loose fill not less than 1in. thick.

There is available in New Zealand to-day an insulating material which consists of gossamer-fine filaments blasted from molten rock by high-pressure steam jets. These particular fibres entrap millions of tiny air cells that form over 90 per cent. of the mass of the material. This insulation is available in the form of handy-sized batts which fit quite easily between ceiling joists, and also in the form of loose and granulated wools to fill between ceiling joists or wall studs. The efficiency of this particular insulating material has been proved in use, and its thermal conductivity at a mean temperature of 100° F. is .3 B.Th.U. per hour per square foot per 1in. thickness per °F. In so far as costs of material are concerned, I understand that the price of the batt for ceiling work is in the region of 1s. 0½d. per square foot, whilst the price of a bag of loose insulation material for walls (one bag will cover approximately 70 square feet, 1in. thick) would be 46s. per bag. There is no doubt that the initial cost of insulation becomes an investment by ensuring an equitable temperature in the home and the saving of costly fuels. In these days of rationing, whether heating be with electric current or gas or coal, some provision for insulation should be made in the original design. The economy thus effected eventually proves of benefit not only to the individual but to the state.

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