Envelope Area Calculations – Perimeters
I have seen people do a very long winded approach to calculating the wall areas of a building and by far the quickest method is to calculate the wall area of a building based perimeters present in the building. An example to this is below with a simple building which has 2 different perimeters.
The shapes of the perimeters with dimensions are shown below:
The trick to using perimeters is to use the total width and depth of the building to calculate the perimeter as these, in most instances, are the same. An example of this is shown below.
Although all sides of the building have differing dimensions for the walls the total width and total depth are identical at 14m and 11m. The perimeter of this building is therefore (14 + 11) x 2 = 25 x 2 = 50m. This can then be multiplied by the height of the storey to calculate the wall area and it is significantly quicker than calculating each individual wall.
Things to be aware of when using perimeters
There is a potential error that can occur when using perimeters, which relates to when you have returns in the building. If you use just the total width and depth of the building you may miss the dimensions for the returns in your perimeter calculation. Consider the example below:
The perimeter of this building is (14.776 + 8.798 + 2.15) x 2 = 25.724 x 2 = 51.448m. This includes the top and bottom width, the left and right depth and the left and right return depths. The mistake here could be to not include the return depths which means the perimeter would be 4.3m shorter than it should be, which would result as a significant error in the envelope calculation.
