Blog
The necessity of insulating even in milder climates.
Talking to friends, I often find people do not see why proper insulation or double glazing matters here. Our winters are mild and short — but they are damp, and the summers get hot.
Damp cold feels far colder than the thermometer says, and you are never quite comfortable. Unheated damp rooms stream with condensation. Then summer arrives and the heat pump goes on to cool the place down again.
Insulation
Proper insulation deals with both problems. The Building Code asks for an R value of 1.9 in the walls, for climate zones 1 and 2. Countries with similar winters ask for close to double that, R 3.5 — which means at least 140mm of insulation. A low-energy or passive house needs around 270mm, but that is another article.
Aluminium windows
Around 95 percent of new buildings in New Zealand use aluminium windows with no thermal break. They are strong and the frames are pleasingly narrow, but heat passes straight through them. The inside face of the frame sits at close to the outdoor temperature, so it runs with condensation in winter and heats up in summer. In other countries these frames are only permitted in internal office partitions.
The fix is thermally broken aluminium, or timber or uPVC frames. Timber insulates best of the three.
Double glazing
Standard double glazing sounds like it must be enough. It is an improvement, but it can be much better: specify Low-E glass, argon filled, with a low-E coating, and you are down to a U value of 1.1 or lower.
For comparison, single glazing is 5.6 and plain double glazing 2.8. Low-E glass in thermally broken frames gives you a comfortable house with no condensation and much less cold radiation. Getting rid of cold radiation altogether takes triple glazing, and the cost of that is still hard to justify here.
U value or R value?
U values measure windows; R values cover everything else — walls, floors and roofs. Confusingly, they run in opposite directions: the higher the R value the better, the lower the U value the better.
Home Concept can work out the R value of any building material, or any combination of them.