Does insulation reduce summer overheating as well as winter heat loss?

Most people think of insulation as something that keeps buildings warm in winter. That's understandable, particularly in the UK and Ireland, and it's by far the most prominent benefit and the one most often cited in energy efficiency guidance. But insulation's relationship with heat isn't one-directional. The same properties that slow heat from escaping in winter also slow heat from entering in summer.

The question of whether insulation helps with overheating is one we're increasingly asked, particularly as UK and Irish summers become warmer and top-floor rooms become uncomfortably hot. The answer is: yes, insulation does help reduce overheating in summer. However, as with most questions of temperature control, the type of insulation and the method of installation matter enormously.