Partial Cavity Fill Insulation on new cavity walls


I have just been over to a community project in Cardiff to have a look at their new building (and old building that is suffering from poor workmanship and maintenance). The new building looks great, but closer inspection revealed a load of issues, but the main one was with the insulation. It is a really common fault and one that drives me mad!

The insulation was, as commonly the case with new buildings, a partial fill in a block work wall using boards. This was designed to fulfil building regs (and no more – another bug bear!) and I am sure that the drawings do fulfil the regs, however the reality will be different. Why? Two main reasons:

1. The boards were not fitted snugly together, so in some areas that I could see there was at least a centimetre gap between the boards. This will create cold spots in building that could lead to damp via condensation. It also severely affects the costs of running the building as the actual build would not meet building regs if this poor workmanship were factored in.

2. The boards that were more snugly put together (not very many from my visual inspection, as most had a 5mm gap between them) were not taped. This allows air to get behind the insulation and again negates a lot of their effect.

If you are to build an extension with these insulation boards that you really need to ensure that:

A. All boards are butted up tight against each other

B. All joints are taped using high quality tape that will last a very long time

C. All insulation is clipped back to the internal wall (this had been done in the case I looked at this AM)

Would you pay to have a cut through of a wall looking like the picture below?? Project management and attention to detail is key and so important to get what you are paying for, otherwise your newly built structure may end up being a real disappointment with much higher energy bills than you were expecting. Be warned!