Unfortunately, there isn’t a relevant industry standard that we can use, but we always carefully analyse two basic points. This analysis quickly determines whether there’s a need to allow for thermal expansion in your design.
Have a facade or louvre design that needs analysis from an expert? Share your plans with us to receive advice from an Insol design engineer. Find out more here.
The points we look at are:
1. How much expansion would you expect?
AS/NZS1664 states that the coefficient of expansion shall be taken as 0.000023/°C.
So, the formula for calculating thermal movement in aluminium looks like this:
length (mm) x 0.000023 x temperature change °C = thermal movement (mm)
So for a 4m length with a temperature change of 40°C:
4000 x 0.000023 x 40 = 3.68mm
It pays to note that the °C of temperature change is metal temperature not air temperature. Metal temperature variations can differ widely from air temperature depending on colour, so this is important to consider.
So, if you’re designing an extruded kitchen drawer handle that is 100mm long and not likely to experience more than 10°C temperature change, then expansion won’t be an issue for you. However, if you’re designing an external vehicle component that could be painted black and used in areas with extreme temperature variations, start thinking about how you’re going to design around the movement.
2. What are the consequences of the movement?
Thermal movement is a hugely powerful force, which can damage your design if it is not accommodated for appropriately.
Consider some of the following:
Now, to apply these two points to aluminium louvres and other sunshade structures.
Louvres are not normally part of the weathertight envelope like roofing, cladding, or windows. They are normally wholly exterior elements with space to move and good airflow all round which helps reduce the temperature change. However, because louvres are external, could be dark in colour, and could be located in areas of extreme temperature variation; they still have the potential to experience high thermal movement and still need to be treated carefully.
Let’s take a look at some non-issue louvres before we look at some critical ones:
The two most critical points to look for are these:
In summary, louvres are typically low risk items and thermal expansion issues are negligible. But be careful! There are some situations that require good design allowances for thermal expansion, and it pays to understand first principles when designing these items.