Cavity Walls and Energy

1. WHAT IS A CAVITY WALL?

Cavity walls began as a form of construction in the 1800s in Northern Europe, becoming common practice in the UK for building in the 1920s and 1930s. As a result, they are a great way to tell the age of a building. Cavity walls are built with two ‘skins’ (outer and inner) with a gap or cavity in between. The walls are held together with ties in regular places. A cavity can range in width from 15mm up to 200mm.

2. WHY INSULATE?

Cavity wall insulation is one of the most cost-effective ways to reduce heat loss from a building. Injecting insulation into the cavity can greatly reduce heat loss from the walls, meaning that homes can be warmed more quickly. This means using less fuel to get to the same temperature in the home.

3. CAVITY WALL INSULATION METHODS?

Cavity wall insulation (CWI) is injected into the cavity via drilled holes in the mortar between bricks on the external ‘skin’. This means no intrusion into the property, although CWI can be done from the inside. There are a handful of different materials used for cavity wall insulation: mineral wool, beads/granules or foam insulation. All materials used for CWI in the UK must be certified by the British Board of Agrément, in order to adhere to legal requirements and receive funding support.

At Avalon Sustainable Energy Solutions we use graphite-coated polystyrene beads (aka grey bead). Not only is this material the best choice for our method of access, being light and manoeuvrable – but it is also a superior insulation product than many other materials. This means even better performance – not just for insulation, but for water ingress and the lifetime of product in situ. Despite our material being an oil based material, we estimate the additional embodied energy of production will be offset through the savings made when used as an insulant.

We always take care trying to match the mortar with our own colours. With abseiling, it is our aim to make our presence as efficient and invisible as we can.

4. FUEL USAGE IN THE HOME – WHY REDUCE IT?

Along with providing a more comfortable living environment, CWI means less fuel - using less fuel can reduce bills and your home’s impact on the environment. Most grid electricity and the burning of gas produce carbon dioxide - CO2 – in production, transport and usage. CO2 is the most measured and famous greenhouse gas which cause climate change. The Energy Savings Trust estimate that a three-bedroom house can save around £140 per year (April 2014). Similarly, less fuel burnt means less production of CO2. Insulating your home can save about the same amount of CO2 as driving a thousand miles per year.

5. HOW MUCH ENERGY AM I USING? AM I PAYING TOO MUCH?

It is extremely useful to know how much you are using so you can see savings. A quick way to see electricity usage is to install an electricity monitor. These are available from many electronics outlets or sometimes via your utilities supplier. Another great source of information is to compare yourself with similar properties. Households use very different amounts of gas and modelling by the Department of Energy & Climate Change (DECC) has found that less than 40% of the variation in gas consumption can be explained by the size, age and type of property, as well as household income and tenure.

6. WANT TO REDUCE ENERGY USE BUT DON’T HAVE THE MONEY?

Beyond changing the fabric of the building, there are a host of low cost/low impact ways you can reduce your energy use without compromising your comfort. Different people lead different lives in the homes. Therefore, what works for one household might not work for another, see our  TOP 10 ENERGY SAVING TIPS.

National Insulation Association

CIGA

BBA Approved Installers

OFGEM Guidance

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