For best thermal performance, position frames near the centre of the insulation line. Optimisation of such details in thermal bridging software is worthwhile. However, deep external reveals increase the solar shading which may or may not be advantageous.

The frame dimensions and the way it opens (inward/outward) will determine how much insulation can be wrapped around the frame. For inward opening windows generally insulate externally; for outward opening windows insulate internally.

Thresholds also need careful consideration as they are a difficult area for achieving good thermal performance.

In addition, airtightness needs to be considered when detailing window installations.

Note that there is little or no benefit to wrapping aluminium-clad frames with insulation externally.

No votes yet