An unexpected problem emerged from the very high wind speeds last weekend. We paid a visit to the site on Sunday and noticed two large piles of polystyrene beads that had been used to top-up the old cavity wall insulation. (the smaller pile in the photo below)



We eventually managed to trace where the beads were escaping - from a small gap in the temporary tape seal around the MVHR Intake Duct. This was small enough for the very light beads to be moved by the pressure difference in the loft space into the main house. Over the course of two windy days the result was a depleted filled cavity though we were partially reassured that this was a small proportion of those added.

This posed a big problem because the beads were added to ensure the cavity was filled to at least the height of the Warmcell that had been blown in the now sealed loft the previous week. Without this cavity fill a potentially very nasty Thermal Bridge had been created at first floor ceiling level - the external air was potentially only around 100mm of brick away from the internal envelope!

So how do you get the beads back. Liam was clear that opening up the loft access and wading through the Warmcell would create many potential problems so he proposed sending the beads back into the cavity the way they escaped. After several frustrating attempts at finding a method that worked Liam thought of using the air leakage testing fan to increase the internal pressure in the house and thereby create a differential pressure between this and the attic space. It worked brilliantly - a tube placed above the container of beads worked like a vacuum and the beads were very rapidly send back to where they belonged.