EWI perimeter+sub-floor insulation with controlled ventilation

Detail for insulation to a ground floor and sub-floor, where the existing internal ground floor void is inaccessible, or it is not possible to lift the whole floor.

To allow the existing ground floor finish to be retained: a granular insulation infill is proposed to prevent heat loss through the floor, with perimeter insulation to footings, used to to prevent cold bridging through the external wall, and the ingress of damp and mould.

The sub-floor ventilation is used to ensure a reduced risk of condensation and humidity build up within the void, using a small humidity controlled fan. (This system can also be modified with temperature and humidity monitoring systems below the floor; as well as additional personal controls for the ventilation fan.)

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EWI Perimeter insulation to footings

Perimeter insulation detail for external wall insulation down to below ground level. Detail for junction between EWI and XPS perimeter insulation for below ground use, providing 600mm maximum insulation below the depth of the internal floor level.

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EWI Plinth Insulation to below ground

Detail for an external wall insulation plinth detail to just below ground level. Intended to ensure water-tightness and prevent thermal bridging to zones under an existing floor by providing continuous insulation down to ground level.

Woodfibre EWI to stop a minimum of 300mm from the external ground level, with XPS insulation fixed using adhesive bond to carry down to below ground level, a minimum 300mm below the internal floor level of the building.

Target Values: 0.2 W/m2K for whole construction.

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EWI to just below ground with plinth and ventilation detail

Detail for external wall insulation to below ground floor level, with a periscopic vent and air-brick installed through EWI to ventilate a basement or cellar. Required where existing air-bricks to a sub-floor space/void would be blocked by the installation of External or Internal wall insulation. Periscopic vents should ensure continued clear air-path to sub-floor, to ensure adequate ventilation.

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EWI Recessed Plinth to just below ground

Detail for external wall insulation plinth to ground, where the internal floor of the building to be retrofitted is solid beneath the internal finished floor level. EWI is carried down to 300mm minimum below internal floor level to prevent cold bridging, but stopped short of external ground level.

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EWI with Recessed Plinth and Periscopic Ventilation

Variation on an external wall insulation detail for periscopic ventilation to a below ground cellar; where the building's internal floor can be insulated to reduce cold bridging through the external wall and below ground. For this reason the EWI to the external wall need not extend below ground level.

A recessed plinth is to be formed with 180mm perimeter insulation below where the 200mm thick woodfibre EWI stops with a minimum of 300mm above ground level; in order to protect the woodfibre insulation from damp and water ingress. A 20mm step provides a feature course as the EWI carries around the perimeter of the building.

A ventilation air brick and sleeve is required where existing air-bricks to sub-floor void will be blocked by floor insulation works. Periscopic vent should ensure continued clear air-path to sub-floor, to ensure adequate ventilation. Insulation to suspended timber floor.

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EWI stop at ground for insulated timber floor

Detail for external wall insulation, with a stop a minimum of 300mm above external ground level. Designed to prevent thermal bridging to zones under an existing floor, in conjunction with an internal insulated suspended timber floor; accessible from above or below.

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