Window renovations & sealants - Tips from the expert

Renovating windows and ensuring they're sealed against drafts is essential. SIGA's expert Hendrik Schimmele shares valuable insights on sealants and the best methods for a perfect application.

Why is the renovation of old windows so important?

Many windows from the 1960s and 70s were not adequately sealed and likely did not have double-glazing. Thanks to double- or triple-glazed windows, a building's airtightness increases, saving energy. Today, it's crucial to minimise energy loss and prevent mould formation. Proper renovation is key, and as an installer, you can make a significant contribution here.

What types of sealants are there, and what are their differences?

There are different sealants for window renovation, each with different properties. Hendrik explains that acrylic is a sealant specifically suitable for indoor use and can be painted over later. However, it's not particularly moisture-resistant and less flexible, making it an older sealing standard. Outdoors, silicones are commonly used, offering better resistance to driving rain and greater flexibility.

An interesting advancement is hybrid sealants, combining the best of acrylic and silicone. These can be used both indoors and outdoors, are paintable, and offer high flexibility. Hendrik recommends products like SIGA Meltell, which can even be used at temperatures down to -10 degrees Celsius and are ideal for joint widths up to 35 millimeters.

How do I effectively seal a window against drafts?

Effective draft sealing is a crucial factor in window renovation. The degree of renovation plays a role here. Hendrik explains, "With a core renovation using a thermal insulation composite system, you can almost achieve the new construction standard. In this case, a joint sealing tape like Fentrim 20 can be used, which can later be completely plastered over." However, for a simple window replacement, different materials are needed. Here, a liquid sealant is the best choice to ensure technical sealing. You seal the joint as follows:

1. Insulate the joint

2. Insert a backer-rod. This can be a PE or PU round cord. Important: Consider the width-depth ratio between the joint and cord.

3. Apply Meltell

Tip: You can use Meltell for wider joints up to 35mm. This can be very helpful, especially in renovations of older buildings.

Conclusion

Renovating old windows is important to increase airtightness and energy efficiency. Proper renovation can help minimise energy loss and prevent mould formation. Choosing the right sealant is crucial, and modern hybrid sealants like Meltell can offer an optimal solution. 

We thank Hendrik for his tips and hope that this article assists you in your window renovation projects. For specific inquiries, feel free to contact us on 0800 434 287.