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Airtight Windows: Sealing Windows to Improve Airtightness


We are building an extension on our stone cottage and are getting triple glazed windows for the extension and existing building. We want to ensure good air tightness around the new windows. What measures do you recommend that our builder undertakes when fitting the windows?

Answer: How To Make Windows Airtight In An Extension

In the new extension I would suggest that you use an airtightness tape such as Contega Solido SL which will create an air tightness barrier between the window and the wall. The tape should be stuck to both the side of the window and the internal masonry wall, which can then be plastered over.

How To Make Windows Airtight In A Cottage

For the existing stone cottage, ideally you should remove the plaster around the window reveals and then use the Contega Solido SL tape in the same way, plastering over the tape afterwards. However, I realise that this is quite a messy/ costly process, which would work well if you are already hacking off the plaster/ adding internal wall insulation or doing other major changes.

Sealing Windows with Airtight Tape

We offer a range of sealing tapes that can be used for a variety of projects. Take a look at some of our most popular products below.

Compego: For Waterproof Surface Bonding

One of our top selling Pro Clima Tapes for sealing DPM or other high gauge polythene surfaces where only surface bonding is required ( Our other Pro Clima tapes chemically bond into the material). It can be used with plastics, plywood, metal, painted wood or smooth concrete and is completely waterproof.

Tescon Profil: For Sealing Window Corners and Joints

The two release paper strips on this tape are used for sealing the corners around windows, and angled joints. It has a high elasticity, which keeps it strong and protects against piercing corners. It can be used both internally and externally and is temperature resistant from -40°C to 90°C.

Tescon No. 1: For Awkward Turns and Uneven Surfaces

This airtight tape is a stretchy version of the Pro Clima Tescon Vana and Tescon Profil tapes – making them perfect for uneven surfaces and awkward joins. It can be used to form a secure seal between foil and fleece membranes, joins between these membranes, and non mineral surfaces. Because of its high elasticity, it offers high protection against piercing, though is easy to tear by hand when applying.

CONTEGA SOLIDO SL/ SL-D: For Sealing Between Walls and Windows

We’ve used this tape alongside others in our Farmhouse Retrofit case study. This is a great tape to use for a waterproof seal between the windows and the walls, and can be plastered over a fleece membrane for extra insulation.

More Of Our Airtight Products

Creating an airtight seal around cottage windows will typically take a few layers of our membranes and tapes. We offer a variety of products that can help to create airtight seals that will keep your home insulated. If you’re having trouble deciding between products, our experts are here to help!

Exterior Membranes

Our exterior membranes provide protection to buildings against harsh weather conditions. The membranes are breathable and diffusion permeable to help protect against condensation risk.

Interior Membranes

Interior membranes help to create an airtight seal within the building. Helping to maintain thermal performance of the building whilst also regulating humidity and providing protection against moisture build up.

Adhesive and Primers

These are used to connect membranes together around windows and provide a smooth surface for tapes and sprays. We offer adhesives that are elastic, offer high adhesion, are weatherproof, and overall help to create that airtight seal that Passivhouse is known for.


While these are not specially for windows, these airtight seals can be used with electrical wires, pipes, and ducts. Using airtight grommets and tapes helps to create a seal around openings so you can ensure your building maintains its airtightness.

Paints or Sprays

Our airtight sprays can be used as an initial airtight layer on areas with cracks to provide excellent vapour control before adding membranes and airtight tape.

All information is provided in good faith. However, any use of the information is entirely at your own risk, no guarantee is given as to its suitability and Green Building Store does not accept any liability whatsoever for building performance or safety, regulatory compliance, or any other outcome which may result from its use or implementation.

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