There is a tendency among builders to skimp on the insulation that they should be installing in every new house, but you can remedy this in your own home at a cost of a few pounds. Proper heat insulation is a ‘must’ in any climate from the Arctic to the tropics-in cold weather it keeps the interior of the house warm, and in hot weather it keeps it cool. If you live in an average British semidetached house with central heating you may be wasting as much as three-quarters of your fuel in heating the air outside your house. It has been estimated that in a house of this type, only 25 % of the heat produced goes to heat the rooms. Of the rest of the heat, 25% goes through the outside walls, 20& through the roof, 20% through windows, doors and chimneys, and 10% through the ground floor. In a terrace house, slightly less heat is wasted than this, and in a detached one, slightly more. In a modern house with large windows, even more heat may be lost.
In any case the annual waste of money is enormous. In a hot climate, of course, the problem is quite the reverse -to stop the sun that beats down on the roof from making the house interior too hot. In some countries. there has been a trend since the Second World War to make roof pitches (slopes) lower and lower sometimes as little as l6 degrees. This reduces the volume of air available as ‘insulation’ between roof and ceiling, and helps make the running of an air conditioning system more expensive than it would otherwise be. The answer to both problems is efficient insulation. Insulating a house properly can reduce heating bills by 35% while keeping the rooms at the same temperature, or can make the house much warmer without using more fuel. Similarly, insulation can reduce substantially the power consumption of an air conditioning system,or, in a moderately warm climate, even make one unnecessary. The greatest fuel savings made by insulation are in houses with central heating. Provided the insulation is done economically, it should pay for it self in two years’ saving on fuel bills. In houses with local heating, such as electric fireplaces or gas fires, people tend to heat only the rooms they use most, and the saving is not so great. But insulation will still make the house more comfortable. Many postwar British houses have a certain amount of insulating material already installed. But standards are not very high as a rule, and adding more insulation is generally worthwhile.
Value for money
An important factor in deciding whether insulation is worthwhile or not is, of course, the cost of installing it. For example, salesmen of double glazing windows and doors often clainr that their glazing halves the heat loss through windows. This sounds impressive until you realise what a small proportion of the total area of a house the windows occupy. Halving the heat loss through them might reduce heating bills by cornparatively little. If this is the case, then obviously it would be better to spend the money elsewhere. Before installing one type ol insulation rather than another, it is a good idea to find out the relative costs ol various n-rethods of insulation, and how ellcient they are. The efficiency of an insulating material is expressed as a’U value’, and the brochures put out by insulating-material manufacturers generally state the improvement in U value obtained by using their material.
U value measures the amount of heat that passes through a material in a given time, so a high U value is undesirable and a low U value is desirable. For example, a properly-insulated lolt floor may have a U value as low as 0.08. If it is not insulated at all, the U value averages 0.43 in post-war houses. The U values quoted by manufacturers for their products are average figures for houses in normal positions. If your house is in a very exposed position, such as on a hill or overlooking the sea, the U value of even the best insulation will be raised, and therefore worsened, by the winds whistling around your roof and walls. You will need more and better insulation. Similarly, if your house is in a sheltered valley and surrounded by trees, you will not need so much insulation to keep it warm-though in fact the more insulation you have, the more heat you save.