EWI from PD Rendering can be used to increase the thermal insulation performance and thermal resistance of external walls.
EWI is the best method to insulate a wall property. It can also be used to refurbish non-traditional housing, do external repairs, or improve buildings with severe heating problems. EWI should not be used on walls that aren’t suffering from rising damp.
An EWI “system” is an insulation layer that is attached to the exterior of the wall. It is then covered with protective and decorative renders, brick effects or cladding finishes.
You can use expanded polystyrene, phenolic foam, or polyurethane boards as insulation. Or you can use mineral wool (MW), batts. A render finish is a cement-based, mineral- or synthetic base coat reinforced by mesh and then over-coated using a primer. The top coat render is applied to the surface and left it smooth, textured, painted, or pebble-dashed. Dry cladding can include timber boards or aluminium panels. Brick effect finishes can include stone, clay tiles or brick slips.
EWI has many benefits, including improved protection of exterior walls from rain penetration, lower heat loss and lower heating/energy bills. It also reduces noise and improves appearance (i.e., greater “kerb appeal”).
Warm walls help reduce condensation and damp problems. They also increase property’s energy efficiency (EPC).
EWI can change the exterior appearance of a property. Most cases, EWI requires planning permission or approval from the local council planning authority before any work can be undertaken. EWI must comply with the national Building Regulations. EWI’s fire classification (largely determined by the materials used) can limit its use in terms both of height and location.
Each property that will be treated should be surveyed before installation. Incorrect treatment can cause damage to the building fabric over the long-term. A competent specialist must conduct a condensation risk assessment if necessary. A vapour barrier between insulation and wall must be installed if the ‘dewpoint’ is found between insulation and wall.
The type of existing walls determines the project-specific choice for EWI. Solid stone walls, for example, may be breathable and allow moisture in to the wall. The wall will breathe if it has a breathable MW insulation and a non-acrylic exterior render.
Brick walls can be resistant to moisture penetration and non-breathable. This wall can be insulated with rigid foam insulation.
To meet the room ventilation needs, extract fans and window trickle vents in high humidity areas must be installed.
Installation is a must for all property fabric work. Poor detailing e.g. Poor detailing, e.g. around the eaves, allows water behind the insulation to get trapped and cause hidden damage to property over the long-term.
