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Window Installation Guide

Airtightness and preventing drafts makes the biggest difference to the comfort and energy performance of buildings and air sealing around windows is a critical part of airtightness strategy. Using the latest Ampacoll Fenax airtightness tapes from Ampack it is quick and easy to make your windows airtight and your openings weather tight.

The guide goes through how to detail around windows which are externally mounted, flush mounted, centrally mounted or internally mounted in both timber frames or in masonry. There is step by step guidance on which tapes and components to use, how to apply them as well as particular guidance on awkward corners and junctions.

The expansion of the Ampacoll Fenax range to include many variations of split backing and also double sided versions is a huge bonus. This allows application of the tape either before installation (using Ampacoll Fenax 30/70 DS) or after installation (using Ampacoll Fenax 12/63, 12/88 or 40/60, depending on the gap around the perimeter of the frame).

The Fenax tape generally requires no primer on timber or masonry surfaces unless they are really friable. Smooth finished plasters and renders are a suitable substrate, as are bare concrete blocks, bare timber and all sorts of timber boards, including wood fibre. Only in the lower density wood fibre boards and sandy surfaces is a primer required. This means window and door openings can be sealed there and then, without waiting for primers to dry which can take many hours in cold, damp winter conditions.

The Ampacoll Fenax tapes are also plaster-able and UV stable meaning they can be used to make external and internal surfaces air and weather tight prior to application of plasters and renders.

When applying tapes to windows prior to installation, the tape is bonded to the frame starting at the top, in the middle. At each corner a 10-15mm ‘pinch’ is put into the tape to allow it to be pressed into the corners once the frame is installed. Once the tape has gone all the way round the frame, a 50mm overlap ensures a full airtight perimeter is achieved.

When applying tapes to the perimeter of a previously installed window, the tape is applied to the opening first by removing one of the split backing release papers. Weather and air tight corners are achieved by creating and inverted pleat. On rough masonry, such as concrete blocks or stonework, full airtightness is achieved by applying plasters and renders.

To see the full Ampack Window Installation Guide guide please click here. If you have any questions about how best to seal around your windows, please feel free to contact us to discuss it.

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