Insulation is arguably the most important factor in making a garden room comfortable year-round. Poor insulation means uncomfortable summers, cold winters, and higher running costs once you're heating the space.
Why Insulation Matters
Good insulation contributes to:
- More stable, comfortable temperatures across the seasons
- Lower heating costs once the room is in regular use
- Better sound dampening from outside
- Reduced risk of condensation and moisture issues
Types of Insulation
PIR Insulation (Polyisocyanurate)
A common choice for garden buildings, PIR boards offer strong thermal performance for their thickness, along with good fire and moisture resistance.
Rockwool / Mineral Wool
Good for acoustic insulation, though it typically needs a thicker wall build-up to achieve the same thermal performance as PIR.
Spray Foam
Creates an airtight seal, but can make future alterations to the building more difficult.
Understanding U-Values
The U-value measures how effective a wall, roof or floor is as an insulator — lower numbers mean better performance. Current Building Regulations set minimum U-value standards for habitable spaces, and a well-specified garden room will generally aim to beat the minimum rather than just meet it. Exact figures depend on the wall build-up and materials used, so ask for the specification in writing rather than relying on a general claim.
Insulation & Plastering: A Selectable Option, Not a Given
It's worth being clear about how this works at LouMil. Every build starts from a base specification — structure, external cladding, EPDM roof, French doors, two full-height windows, delivery and installation — and insulation & plastering is a specification option you choose and price separately through the calculator, giving you insulated walls and ceiling with a plastered internal finish. It isn't fitted as standard on every room by default, because not every garden room needs it: a room used occasionally in summer has different requirements to one used as a year-round office or annexe. If year-round comfort matters to you, make sure insulation & plastering (and, usually, electrics with a heating solution) are included in the specification you're pricing. See our insulated garden rooms page for more on this option.
Don't Forget the Floor
Floor insulation is often overlooked but matters a great deal — a cold floor makes the whole room feel uncomfortable regardless of the air temperature, so it's worth including as part of any insulation specification rather than treating it as an afterthought.
