A thermal bridge is any strip of material that conducts heat faster than the insulation around it — a hidden shortcut for warmth to escape from inside to outside. In stud-frame garden rooms, the biggest thermal bridge is timber itself: every stud in the wall is roughly 3× more conductive than the mineral wool packed between them.
Why this matters in the real world
In a typical timber-frame wall, roughly 12-15% of the wall area is solid timber (studs, top and bottom plates, headers). That means 12-15% of the wall is losing heat at 3× the rate of the rest. The overall U-value of the wall — the number engineers use to compare thermal performance — is 20-30% worse than the insulation alone would suggest.
How insulated timber-frame builds fix this
- No studs — the panel is continuous PIR core with no vertical timber to conduct heat
- Spline joints — where panels meet, the joint is filled with insulating foam, not solid timber
- Corner details — engineered to keep the insulation continuous around every corner