Cavity Wall Insulation (CWI)
Expanding foam insulation to pack the whole cavity
In the early days of grant-assisted cavity wall insulation, when a whole house could be insulated for a couple of hundred pounds in just a few hours, the products used were naturally the cheapest available, either loose beads or blown fibres. Now 5 or 10 years on those cheap products are starting to become expensive problems.
Loose beads settle over time leaving uninsulated gaps, particularly around the top corners of the walls and below window frames. If you drill into the wall to fit a new pipe or cable, it's like drilling into an egg timer. Beads trickle out until large sections of the wall are empty. Blown fibres tend to pack the area around the drill holes rather than spreading to give a uniform fill throughout the wall. Fibres have a habit of slumping over time inside the cavity too, meaning you end up with a cold spot along the top of the wall. As the fibres become densely packed at the bottom of the cavity the soggy mush becomes a cold bridge to let even more heat out. If you've a path or flowerbed touching the bottom of the wall or there are any flaws in the damp proof membrane moisture tracks through the packed fibre insulation causing mould issues inside the property.
In short, cheap cavity wall insulation is cheap for a reason. What may have started as reasonable protection from the cold can gradually become a problem that's difficult to rectify. Fortunately there is a solution.
Expanding foam insulation
To achieve the best performance the cavity wall needs to be packed fully with a high grade insulation product, ideally a product that expands when injected into the cavity to fill every nook and cranny. Expanding foam not only seals tightly around window and door frames, it also bonds the inner and outer wall together to improve structural integrity. The airtight vapour barrier solves insulation and settlement problems permanently.
Solarcrest recommend the BASF Walltite CV100 cavity wall insulation system for all cavities from 40-200mm, hard-to-treat cavities, or for properties looking for maximum airtightness and minimum U-value. Our theory is that a cavity wall can or should only be filled once; you only have a limited space available; and Walltite offers higher thermal resistance than any other cavity product. BASF Walltite is BBA approved both the roof and cavity walls.