Compact Building Forms

Compact form is the most basic strategy for conserving heat. This is because heat loss increases with surface area. This shows up in the Q = UA (Delta T) equation, but we all know it instinctively – it is why mittens are warmer that gloves;  why cold fingers close into fists; and why dogs and cats curl up on cold nights, or sprawl loosely on hot afternoons.

A cube is a compact form – if  a slice is removed, its volume goes down, but it surface area can go up. This is not to suggest that buildings need to be blocky – there are good reasons for them not to be – but it does emphasize that form effects energy  use, and choices about form should be made with this in mind.

It is also true that larger forms enclose space more efficiently than smaller ones. In the example below, the eight cubes represent standalone houses. If eight row houses were built instead, the same amount of space could be enclosed with 29% less surface area; and, if apartments were built, the same space might require 50% less surface area. This means that the apartment would have 50% less  heat loss while using the same wall, roof, and floor assemblies. This also means that, if saving energy is a priority, attached housing should be considered.