week 22: early results on cavity wall insulation

December (Pre- Cavity Wall Insulation)  January (Post Cavity Wall Insulation)

At the beginning of December, not long before the cavity wall insulation was injected, I took the opportunity to take some thermal images of the house. As the image above left shows, we had a significant amount of heat loss through the cavity. Warm air (shown yellow/ green) was entering the cavity and escaping at high level.

I carried out another survey earlier this week (cavity wall insulation has now been injected – see earlier post). The image above right shows the same north gable wall. There are no yellow/green areas at all, which suggests that the cavity fill has significantly reduced the air movement within the cavity. This is the primary purpose for the cavity fill, otherwise the external wall insulation (to be fitted shortly) will be less effective.

The area highlighted by a red arrow indicates an area of higher heat loss at the front of the house (you may need to click on the image to enlarge it). This area is a small solid wall section and again illustrates the the effectiveness of the cavity wall insulation elsewhere. More images to analyse and post later.

One final thing for now on cavity wall… we had the opportunity to look into the cavity again as we are changing the aperture of one of the windows. The ecobead insulation again beats my expectations and has completely filled the entire cavity:

Existing kitchen window

week 17: cavity wall insulation

CWI injection  CWI Injection at high level

The cavity wall insulation (CWI) has now gone in. Primarily, it will be the external wall insulation that will be providing the heat loss reduction and achieving our U-values of <0.14 W.m².K. However, in order for the external insulation to be effective, we need to fill the cavity as best as possible to minimise/eliminate air currents. Otherwise, warm air entering the cavity will rise out at the cavity head to atmosphere, bypassing the external wall insulation. The picture above right shows the insulation being injected above the ceiling line of the top floor (usually installations stop just above ceiling level). This is in order to reduce air currents all the way to the cavity head.

We have selected Platinum Ecobead as the CWI insulant. These are expanded polystyrene spheres that are injected at high pressure into the cavity – the manufacturer’s claim this totally fills the cavity, which is good. It is also blown with an adhesive, which means that the beads will stay in place, and not slump, when it dries. As we are replacing the windows and sills, a few days after the CWI installation, we get a unique opportunity to look inside the cavity to see how well the Ecobead has filled it. I am impressed!

viwew of cavity at window sill