Window Mounting Tapes: How to Properly Insulate Windows and Save on Heating Bills
Window mounting and insulation tapes are an essential part of any professional window installation process. Alenor offers a complete product range — from specialised internal and external window tapes to universal mounting tape solutions for façade and wall work.
Browse Alenor's full range of window tapes and mounting tapes to find the right solution for your project. Proper window insulation isn't complicated — with the right materials, it can be done even by yourself.
Installing new windows is a significant investment in your home's energy efficiency and comfort. But even the most advanced A+ energy-rated window cannot fully do its job if gaps remain in the joint or surrounding structure. That's where window mounting tapes come in — specially engineered materials that create an airtight seal around the window, both outside and inside.
In Latvia, where the annual temperature swings from -25°C to +35°C, proper window insulation isn't just a comfort issue — it's an economic decision. A poorly insulated window can increase heating costs by 15–30%, cause condensation, mould, and structural damage. In this article you'll learn which mounting and insulation tapes for windows are the right choice, and how to install them correctly.
Internal and external window tape — what's the difference?
Professional window installers always use two types of tape — internal and external. This principle comes from a basic law of building physics: a window joint must be more airtight on the inside than on the outside. That means the internal window insulation tape must block both air and vapour completely, while the external window tape must be vapour-permeable, so moisture from the structure can escape.
If this principle is ignored and only one tape is used (for example, only the external one) or ordinary film is used instead, moisture gradually builds up in the joint, mould forms, and wooden structures can start to rot. That's why a correct window mounting process always includes both an internal and an external tape. These two tapes are often also called window sealing tapes or diffusion tapes for window installation, depending on whether we're talking about the vapour-barrier (internal) or the vapour-permeable (external) solution. Whatever the name, the principle stays the same: tighter on the inside, more permeable on the outside.
Alenor window tapes: a professional solution for homes and commercial buildings
Alenor internal window tape — full-width adhesive vapour barrier
The most effective way to seal the inside of a window joint is with the Alenor internal window tape, which has adhesive across its full width. Unlike standard tapes where the adhesive is only along the edges, this tape's entire surface is coated with adhesive, ensuring a completely airtight bond with both the window frame and the wall structure. Alenor's internal vapour-barrier tape for windows is made from a flexible material that bonds well to wood, concrete, brick, and PVC surfaces.
Alenor external window tape — UV-resistant outdoor protection
For the outside, the Alenor external window tape with full-width adhesive is resistant to UV rays, rain, and temperature swings. It allows moisture from the joint to evaporate outward freely, while keeping water from getting in from outside. This window mounting tape meets European DIN standards and is suitable for use with PVC, wood, and aluminium window constructions.
Mounting tapes for windows: N-Flex, M-Band, and Duo-Band
Alongside the dedicated window tapes, Alenor offers several universal mounting tape solutions suitable for sealing windows, doors, and façade structures.
Alenor N-Flex is a synthetic rubber insulation tape specifically suited for preventing condensation and thermal bridging. Thanks to its flexible structure, it bonds well to uneven surfaces and resists moisture, temperature fluctuations, and chemical cleaning agents.
Alenor M-Band is a non-woven acrylic tape that serves as a reliable joining tape for diffusion membranes and finishing materials. It provides an airtight bond that's essential in window construction, where even the smallest gap significantly reduces energy efficiency.
Alenor Duo-Band double-sided acrylic tape is the solution when a strong bond on both sides is needed — for example, fixing a diffusion membrane to a frame or window sash. This double-sided adhesive tape is flexible and withstands the movement caused by thermal expansion.
How to properly install window mounting tapes
Installing window tape isn't complicated, but it requires care and the right sequence:
Prepare the surface. Before applying the tape, the wall and window frame surface must be clean, dry, and free of dust.
Start with the internal tape. Before the window is fitted, apply the vapour-barrier tape to the inside of the frame or opening.
After installation, apply the external tape. Once the window is fitted, seal the outer joint with the external diffusion tape.
Press firmly. Use a pressure roller to ensure full adhesion.
Avoid stretching. Apply the tape with a little slack so it can accommodate movement.
Benefits of proper window insulation
Using window mounting and insulation tapes correctly brings several benefits. First, a significant reduction in heating and cooling costs — an airtight window is just as effective as thicker wall insulation. Second, prevention of condensation and mould problems, which benefits both the building's durability and residents' health.
Third, better sound insulation — an improperly sealed window is a major path for outside noise. Using double-sided tape together with specialised window tapes can significantly improve sound insulation, even without replacing the window.
Read also: Why external window tape is just as important as the window itself — learn more about the technical structure and application of the external tape.
Summary: the right tape in the right place
The core rule is simple but easy to skip: seal tighter on the inside, and let moisture escape on the outside. Get that internal/external pairing right, and the window joint stays airtight and mould-free for the life of the window — not just for one heating season.
Browse Alenor's full range of window tapes and mounting accessories to find the right combination for your project — most homeowners can install them correctly with basic tools and a bit of care.