Midcoast Green Collaborative Forum

September 9, 2008

Sustainability Post #31 – Building Shape Efficiency.

Filed under: Conversation, Philosophy — Tags: , , — Topher @ 9:57 pm

While looking at a number of local houses, I noticed the degree to which they suffer from inefficient shapes.  Lots of corners, lots of wall surface area, not much enclosed volume.  Thus hard to heat.  I decided that I needed a numerical value for this concept.  Building Shape Efficiency is thus defined as Enclosed area / (Perimeter / 4) ^2.   A good house should have a Building Shape Efficiency of 93% or more.  Some I have done audits on are under 45%.

How does your house shape up?

p.s. I make no claim to being the first to invent this metric.



  1. Eeeeek. New ’round these bloggy parts.

    This measurement is making my head explode. Are these numbers — “enclosed area — supposed to be off the top of my head?

    Help, please.

    Comment by leolabeth — September 24, 2008 @ 1:22 pm

  2. Not really. The enclosed area, footprint, or floor area of the building can be measured. Divide the house up into rectangles and measure and multiply length by width for each, and add those all together (best if measured from the outside). Only one floor is measured. Often this is the figure they use in realty papers when you bought the house. The perimeter is just the length of the exterior wall. Start at one corner and keep adding up wall lengths until you get back where you started.

    Divide the perimeter by 4, and multiply that result by itself. Divide the floor area by that. That is you building shape efficiency.

    For example, my house is 26 by 38 feet on the outside. That is 988 (26 x 38) square feet of floor area. And a perimeter of 128 (26 + 38 + 26 + 38) feet. Divided by 4 is 32 feet. Times itself is 1024. 988 divided by 1024 is 96.5%

    Hope this helps.

    Comment by Topher — September 25, 2008 @ 10:55 am

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