How To Make A Window Reveal

If you are converting or refurbishing a building, knowing when to insulate reveals and what's acceptable is key to ensuring defects don't occur. Because let'due south face it the final thing yous want is a build-upwards of condensation leading to potential mould growth.

We have put together some guidance to help you determine the necessary standards when insulating window reveals in refurbished buildings.

What is an acceptable level of insulation to a reveal?

Building Regulations Approved Document Part L1B recommends that the minimum performance of whatever insulated element should accept a U value no worse than 0.7 W/m2K. This U value should be used as the minimum standard for a window reveal.

So what does that equate to in insulation thickness?

This depends on the thermal performance of the existing structure and and the quality of the insulation product.

Equally an example if insulating a 225mm solid brick wall using phenolic or polyisocyanurate (PIR) insulation, then a typical insulation thickness would be 20-25mm.

What other considerations should be taken into account?

Provision of vapour control - should be continuous throughout the insulation layer.
Width of window frame jamb - needs to exist wide plenty to support the reveal.
Plaster dabs should exist avoided - particularly where the damp proof course (DPC) effectually the window is not axiomatic.
Applying insulation directly to the wall - some insulation products can be applied this way. If non the independent lining should be continued around the reveal.

What if the existing windows are to be retained and the jambs are as well narrow?

There are a number of products on the market place which are thinner for utilise with narrow reveals, including some multi foils. However before considering whatever of these products make sure they have tertiary party certification.

If this is not possible, you should carry out a condensation risk analysis to support the proposed solution.

What if the walls are to be thermally upgraded but not the windows?

This poses a greater risk every bit the high performance of the upgraded walls could further exacerbate the problem so it is important to obtain a specialist written report.

In the case where the walls are to exist upgraded externally, the internal reveal doesn't need to be insulated, but the external wall insulation must be continuous and finish at the junction with the window or door to prevent a cold bridge.

What about cavity walls that have been insulated using blown insulation?

You will withal demand to insulate the reveal unless the reveal incorporates an insulated cavity closer.

Can a robust detail exist acceptable for this construction?

No, the robust details scheme simply applies to new structure work and is non suitable for internal solid wall insulation.

If you lot have whatever questions about insulating reveals we'd love to hear from you.

References

BRE 262 Thermal Insulation: Fugitive the risks
Building Regulations Canonical Document L1B

By Frzana Ferguson

Please Note: Every care was taken to ensure the information in this article was right at the fourth dimension of publication. Any written guidance provided does not supplant the reader's professional sentence and any construction project should comply with the relevant Building Regulations or applicable technical standards. However, for the most upwardly to date LABC Warranty technical guidance please refer to your Take a chance Management Surveyor and the latest version of the LABC Warranty technical transmission .

Source: https://www.labcwarranty.co.uk/blog/dont-be-exposed-know-how-to-insulate-your-window-reveals/

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