Left in the cold

The importance of insulation

Local architect and insulation specialist, Ken Davis, introduces us to the importance of good insulation when embarking on refurbishment, renovation and building projects – and when considering energy efficiency and saving money on heating bills. This is the first in a series of articles about the necessity for good insulation.

Imagine if you will, on a freezing cold winter’s day, going outside with just some shorts and a T shirt on! Now, if you had any sense you would of course rush back inside and put on some more clothes, even several layers, to keep yourself warm. You would know instinctively that to stay alive, you must keep up your core body temperature. And yet, knowing this, many of us live in buildings which leak heat just like poorly clothed bodies and, in so doing, cost us a great deal in terms of poor health and unnecessarily high extra living costs, let alone the wider negative effects on our environment.

Many of the buildings in Hastings are old and many are of some historic significance, but they were largely built in ignorance of the need to keep warm in order to function well and to stay healthy; our economy was poor and people simply died young.

In order to keep to a simple model, let us consider what is probably the most common building type in the town – and to look at the outside walls, which are probably made of a single brick with some internal plaster. There are, of course, many variations on this.

In a similar way to water always searching out a lower point to move to, heat will always move towards a lower temperature area in order to even out temperature variation. There must now be some technical explanation if the true value of insulation can be appreciated. I think it is fairly obvious – common sense if you like – that high density materials such as steel, concrete and brick will have what is called ‘high thermal conductivity’, meaning that heat will pass through them quickly, while lighter and less dense materials such as wool, woodfibre and polystyrene will have low thermal conductivity, that is heat will pass through them more slowly.

The thermal conductivity of brick is 24 times worse than mineral wool! Heat whizzes through a solid brick wall! And we have many such houses in Hastings that have not much more than a brick wall from inside to outside.

However, walls need to have structural and weatherproofing properties as well as thermal insulation properties, and this is why most modern wall constructions are therefore composed of a number of layers. The thermal resistance of those different layers must be added together to give an appropriate overall thermal resistance.

So what makes these lighter materials such good insulants? Very simply it is the presence of air within them and that is obvious enough if you pick up wool or some of the man-made foamed materials such as polystyrene. And the reason air, within a matrix of other materials, can slow down heat flow so effectively is that it has to change its method of movement each time is goes from air to wool fibre or air to the thin plastic skin of one of the bubbles in polystyrene.

But that perhaps is enough of the technicalities of this explanation for now, not least because we will also have to deal with the way air moving across a temperature gradient in a wall (or roof or floor) also changes the way it holds water – and also because heat likes to find direct ways of balancing itself out, simply by searching out air gaps in buildings. Both of these have implications for the health of the people inside and the building itself.

Contact Ken Davis via kgdavis129@gmail.com

Also in: Energy Wise