Mistakes made regarding insulation

Mistakes made regarding insulation - how it can affect a garden room or garden office.

Nearly everyone wants to do their bit towards the environment and save on heating bills at the same time, so what should we look our for when talking about insulation? Particularly when you are building a garden office.

Well, first of all you need to bear in mind that no matter how good your insulation is, the effect of it will be cancelled out if you have too much glass.

Amazing claims are often made about double glazing, special coatings added within double glazing. Some people are hyping up treble glazing as the goal, (some even quadruple glazing).

This is all very well, and is certainly good for the people supplying glass and glazed units, but even quadruple glazing remains the coldest surface in a room, after all that!

So if glazing is the coldest surface, the heat in a room will be contained initially by the warmer surfaces and properly insulated walls and roof, but when the air circulating in the room moves over towards the glass surfaces, the heat begins to bleed away, it circulates back to the rest of the room, just a bit cooler than before, until it meets some glass again and loses a bit more heat and so on.

This is simple fact, so when reading the claims made by anyone regarding the insulation figures of their materials, bear in mind that they often choose what the non-glass surfaces are made of. This shows them in a good light, but it can be misleading, since the truth is actually the figure for the whole room or building, this is the real answer, and the one that determines what your heating bills will be.

This is for buildings that are draught free of course, otherwise the figures can get a lot worse. The more glass and draughts, the more irrelevant the insulation figures become, since they nearly always refer only to the warmer materials in the building/room. So it is often a false picture.

Here's a little test for you:

Which building/room will be warmer out of these two identical designs below?

• One with 20ft thick hyper-insulated walls over 25% of the area, with 75% glass surface area on all walls,
• Another with an ultra slim 2 inch thick wall with an inch of insulation over 75% of the area with 25% glass surface area?

You guessed it, the answer is the badly insulated wall with just 25% glass. The insulation keeps the heat in but the glass loses it all so there ends up being no heat for the insulation to keep.

Insulated roller blinds are one answer, they re-balance the room thermally, making the window areas many times warmer than even quadruple glazing. Trouble is, who wants to close the blinds and thereby black the windows out during the day?

Solar gain is another problem with large expanses of glass as you have a greenhouse effect and can 'fry' in the summer, especially if your studio faces south.

We use tinted glass more and more as the solar glass itself is so dear and a plastic film on the inside of the glass reduces solar gain a lot. Plus we can use heavier or lighter tints depending on which direction the glass is facing. This also has a slightly better effect in winter as the plastic film on the inside face of the glass is warmer to the touch than glass alone.

Never mind all the claims and the science - do a low-tech test, just put the back of your hand against any window in your house.

So it's worth remembering that the figures that tell the true story, are the ones for the whole room, based not just the warmest parts, but taking into consideration all the surfaces.

The moral of the story?

When specifying a garden building, don't forget to talk to us. We can help you get the balance right and unravel the claims and figures, so that when your building is finished it will be as economical as possible to heat in the winter and as cool as possible in the summer.

Author: David Fowler