Insulation and Airtightness: Second Retrofit Solution Agreement

The second Agreement from Procurement for Housing & Fusion21's Retrofit Solution encompasses Insulation and Airtightness. The framework will cover the supply and/or installation of the energy efficiency products in the following categories:

Internal wall insulation
External wall insulation
Loft insulation for 'more advanced applications'
Air tightness and draught-proofing products

These products are all installed as part of a low carbon refurbishment package for existing housing stock helping to make them energy-efficient and reduce carbon emissions.

Internal Solid Wall Insulation (IWI) is cheaper than its external counterpart and will not alter the external appearance of the property. Its installation is, however, more disruptive to occupants and will minimally reduce the available floor space. The two typical types of internal wall insulation are:

Stud walls
Rigid Insulation Boards

External Solid Wall Insulation (EWI) is installed as a combined package of insulation material and the render, or external cladding, which is referred to as an EWI system. The three typical types of External Wall Insulation Systems are:

Wet render systems
Dry cladding systems
Bespoke systems

In an EWI system, the insulation layer is secured to the existing wall. Then, either a wire mesh or plastic scrim, is fixed to that which the wet render system is applied, or a dry cladding system is applied. Dry cladding systems allow for greater flexibility of external appearances which can be particularly beneficial if planning constraints apply to the finish of certain buildings.

Loft Insulation: lofts are notoriously cold spaces generally used for storage. To insulate, typically, layers of mineral wool (fibre glass) are laid between and perpendicular to the joists. Using insulation in this manner dictates that the loft cannot be accessed further but very low U-values can be achieved (the lower the U-value, the less heat is escaping).

If a loft needs to be kept accessible, there are two approaches: if it is purely to be used as a storage space, the joists can be built up so that sufficient insulation can be laid down. If the loft is to be used as a room then the insulation is to be installed on the level of the rafters.

Air Tightness: up to a third of heat losses from modern buildings can be attributed to air leakage. The 2006 Building Regulations in England and Wales have a required air tightness of 10m3/m2/h at 50 Pa for all new buildings, but no such standards exist for retrofitting existing housing stock.

Increasing air tightness can also cause problems if not carefully regulated: improving air tightness without enhancing background ventilation can lead to condensation, mould growth and eventual structural degradation - as well as potential health problems for residents.

Therefore advanced air tightness measures must be supplemented with criteria such as trickle vents or mechanical ventilation systems.

The PfH/Fusion 21 Insulation and Air Tightness Agreement has used extensive research and set exacting standards for suppliers to fulfil in order to ensure effectiveness, safety and low U-values. The Agreement will be launched in July and further information will be available to Members next month.