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Whilst External Wall Insulation (EWI) is known to provide added thermal insulation to reduce heating bills in winter it is lesser known fact that EWI can also improve comfort levels in summer by helping to keep the sun’s heat (solar gain) out of buildings and will also reduce the need for mechanical comfort cooling via air conditioning.

This is achieved by the following EWI advantages:

Thermal Mass and Heat Storage: One of the primary reasons External Wall Insulation is effective in reducing heat gain during the summer months is its ability to alter the thermal mass of a building. Thermal mass is the ability of a material to absorb, store and release heat. Materials such as concrete, bricks and tiles absorb and store heat. They have therefore said to have high thermal mass. Materials such as timber and cloth do not absorb and store heat, so are said to have low thermal mass.

When EWI is installed, it increases the overall thermal mass of a building. This helps slow down the transfer of heat from the outside of the building to the inside. This delay in heat transfer means that the peak indoor temperatures are reached later in the day, which subsequently reduces the amount of time spent in hot conditions that may prove to be uncomfortable.

Thermal Resistance: Another key factor in EWI’s ability to reduce heat gain during the summer is its thermal resistance. This is a measure of a material’s ability to resist the flow of heat, which is expressed as an R-value. The higher the R-value, the greater the insulation’s effectiveness in resisting heat flow.

By installing EWI with a high R-value, you can make significant inroads into reducing the rate at which heat enters your home or building from the outside. As a result of this, a cooler indoor temperature is established.

Air Leakage Reduction: In addition to providing a thermal barrier, the application of a quality External Wall Insulation can also help to reduce air leakage. Gaps and cracks in a building’s structure can allow hot air to enter during the summer months, thus making it harder to maintain a comfortable temperature.

When EWI is installed, it can effectively seal these gaps and cracks, which in turn then cuts down on any infiltration of hot air and helps maintain a more stable and comfortable internal situation.

Reflective Properties: The external layer of EWI systems can also have reflective properties that help to minimise heat and solar gain.

The protective render or cladding layer can be designed with what is known as a ‘high solar reflectance index’ (SRI). The SRI measures a material’s ability to reflect solar radiation.

By reflecting more sunlight away from your home or building, EWI systems with high SRI values can further reduce the amount of heat that is often absorbed by your walls and ultimately transferred to the interior.