Low Energy House

Low Energy House - About Loft Insulation - New Build

The performance of a thermal insulation material relies on the amount of air trapped within it. If that air is kept dry and still, less heat can get into or past the material and the higher its insulation capacity will be

Glass Wool Loft Insulation - Image Provided by KnaufCold Roof - Loft Ventilation

Ventilated cold roofs usually have ventilators fitted at eaves level and in the rafter feet to allow the outside air to flow naturally across the loft space. The free passage of air helps remove condensation, prevents moisture entering the loft insulation material and stops mould growth and rot affecting the timbers.

Installation of Loft Insulation

In lofts, the insulation is typically installed in two layers. The first layer is laid between the timber joists at the loft floor level. Because heat can be lost through the joists themselves a second layer of loft insulation is laid across the top of the joists, at right angles to them.

Building Regulation Target Emissions Rates for Loft Insulation

Current Building Regulations require new dwellings to be compliant with an overall energy and carbon performance with the Target Emissions Rate (TER) based on the whole building envelope. Thermal U-values for individual elements are not, therefore, set for new houses. In order to achieve the overall standard, new dwellings will usually require the loft floor insulation to achieve a U-value of 0.16 W/m²K.

As an example, a typical specification for a loft, to comply with this target, would be a minimum total 270mm thickness of glass wool quilt.

Materials Commonly Used for Loft Insulation

Glass Wool Loft Insulation
Glass fibre quilt rolls laid in two layers over the loft floor
Loose glass wool fibre for hand filling or blown into place by specialist machine

Rock Wool Loft Insulation
Rock wool quilt rolls laid in two layers over the loft floor
Loose rock wool fibre for hand filling or blown into place by machine

Cellulose Loft Insulation - Recycled Newspaper
Dry cellulose supplied loose for hand filling or blown into place by machine

Sheep Wool Loft Insulation
Lightweight sheep's wool batts laid in two layers over the loft floor

Because of its nature, where loose fibre is used it will form one continuous layer of insulation.

Quilt or blanket loft insulation is supplied in rolls approximately 400mm and 600mm (16 inches and 24 inches) wide and in a variety of thicknesses. Loose fibre fill is supplied in bags for hand filling or can be blown into position, by a registered installer, using specialist equipment (Guarantees for this work are available from the registered loft insulation installer).

All loft insulation materials must be fitted in accordance with the manufacturer’s instructions

Loft Insulation - Best Practice

The thickness of the loft insulation may be increased to improve the thermal comfort of the dwelling and to save more energy. In the context of a loft insulation project, additional thicknesses of insulation can be installed at relatively little extra cost.

When an appropriate system has been chosen, it is important that the edges of the loft insulation are lapped with the wall insulation to ensure continuity of the insulated building envelope. It is important that the insulation does not block the air vents at the eaves

About Loft Insulation - House Insulation - Home Insulation