Cavity wall insulation is method used to reduce heat loss through the walls filling the air space with material that inhibits heat transfer.
Heat loss by convection and conduction
Cavity walls are constructed in houses. It is an outside wall and an inside wall with a space between the two walls which is air. This is known to be an effective way preventing of the wall inside house from becoming damp however the air gap can transfer heat by convection making the house colder.
Heat loss through walls can be reduced using cavity wall insulation .Cavity wall insulation is filling the space in between the walls with polymer foam. This reduces the heat loss by conduction. The foam is a plastic material that causes air to be trapped inside it. The foam replaces the air in the gap between the bricks. Foam also prevents air from travelling inside the cavity, therefore causing it reduce heat loss by convection this involves blowing insulating material into the gap between the brick and the inside wall, which reduces the heat loss by conduction. The material also prevents air circulating inside the cavity, therefore reducing heat loss by convection .This causes Conduction heat transfer to be poor due to the polymer and the trapped air are good insulators. The room in the house stays warmer for longer.
Heat loss by radiation
Double glazing windows which have two layers of glass with a space between them are designed to reduce loss of heat and exclude noise. Glass layers together with a small air or gas filled gap between them are referred to as Double Glazing. The panes of glass are sealed at low pressure and the air is dried to avoid the misting up of the component.
The air trapped inside the window acts as insulator and does not stop heat loss being conducted from inner glass plane to the outer glass plane but reduces it by a significant percentage. As the air gap is very narrow, the air cannot circulate freely and thus reduces heat loss by convection as well. The radiation heat loss is merely reduced by efficient double glazing. It is found that almost 54 to 64 percent total heat loss can be reduced through Efficient Double Glazing.
Heat loss by conduction
The trapped air in the gap is an insulator – it does not stop heat being conducted from the inner pane to the outer pane – but it does slow heat transfer by conduction down a lot!
The air gap is too narrow to allow the air to circulate easily. This therefore reduces the rate of heat transfer by convection.
The trapped air reduces the rate of heat loss through the window by conduction and convection. The room in the house therefore stays warmer for longer reducing heating costs.
Heat radiates through air and glass – as it does so some of it is reflected (but this is virtually the same as for single glazing) and some of it is absorbed (mainly by the glass itself) this percentage increases as there is more glass. But overall heat transfer by radiation is hardly changed by double glazing a window – it is conduction and convection that change the most!
The space between the roof and the ceiling is called the loft. Glass fibre or other loft insulation materials are laid across the loft to reduce the rate of heat transfer out of the roof. Glass fibre works as an insulator by trapping air. The glass fibre with trapped air is a very poor conductor which reduces heat transfer from the ceiling to the loft. The room in the house stays warmer for longer
Loft insulation works by reducing the amount of heat lost from your roof – reducing the amount of fuel you need to burn for heating and saving you money.
When your home is heated, a lot of that heat escapes through your roof, both through conduction and convection. Laying loft insulation in your loft reduces the amount of heat that passes through your ceilings and reaches your loft space to escapes through your roof – it traps the heat inside the rooms below the loft.