What is cold bridging and how does it happen?

Cold bridging happens when a warm surface or structure meets a colder one. Put simply it’s a weak spot in the insulation surrounding a house, known as the thermal envelope.

Cold bridges (also known as thermal bridges) occur whenever there is a break in the continuity of the insulation. The break can be caused by elements interrupting or penetrating the insulation like:

• Pipes and cables
  
  
• Windows and doors
  
  
• Balconies
  
  
• Studwork in timber frame walls
  
  
• Junctions between roof and wall, or wall and floor

The moisture in the air clings to the coldest surface and often the first sign is the formation of black mould around skirting boards and window openings.

Good design and workmanship should prevent cold bridging and it’s something that your building control surveyor will be looking out for on their site visits.

Further information

What are the key issues in design and construction?