Anchoring external blinds into thermal insulation: is it a problem?

When retrofitting external blinds, the holders and guide profiles are anchored to the window frame or thermal insulation. If everything is done correctly, this intervention will not affect the insulation function of the window or the façade. For 100% certainty, you can also arrange with the contractor to use special anchors to break thermal bridges during anchoring.

Ideally, anchor everything to the window frame

In the case of retrofitted and visible blinds, it is usually best to have the installer anchor all the elements and holders to the window frame. This is because the window is always straight, strong and stable, so you can be sure that the blind and the cover sheet or box will hold without any problems.

“We can anchor into plastic, wooden or aluminium windows, depending on whether we use galvanised or stainless steel anchors. Some clients are afraid to drill into windows, but this is unwarranted — the window is already factory-drilled for the fittings, so our intervention will not damage it,” says the managing director of RENESUN Žaluzie, René Býma, who has been installing external blinds for 20 years and has not yet encountered any problems with insulation caused by anchoring into the window. Just count on the fact that the window frame surface will be disturbed and if you want to remove the blinds in the future, for example, you will be left with holes in the frame that are harder to fix than holes in the façade.

The cover plate and the blinds are always placed inside the window openingwhen anchored to the window. You should therefore expect to reduce the window clearance from the top by approx. 20 – 30 cm.

View of the guide rail, which is anchored to the window frame via holders.

If you would like to anchor the holders to the reveals (jambs), this is also possible. In this case, for example special anchors called “TURBOLET“are used, which also hold well in softer material. However, in the case of poorly made façades, it may occur that the holders do not hold firmly enough, so anchoring into the windows should be considered. “In any case, the insulating properties of the façade will not be compromised by this, it’s a minimal intervention that has no effect,” says Býma.

Another option is to place the external blinds above the reveal (and not inside the window opening). This is particularly useful if the window opening is shallow — less than 13 cm deep — and the sheet metal cover and the blind would not fit inside, or would protrude in front of the façade. In this case, the cover and holders are anchored from the front side into the façade.

Front installation on the façade

In this case, the cover box or sheet and the guide profiles are placed in front of the window opening and all elements are anchored to the façade from the front. According to Býma, this is again not a problem and the insulation function of the façade is not compromised. What is more important is that everything holds well, so it is advisable to drill through the façade to the underlying masonry or lintel.

“If the customer is worried about drilling through the façade, we can choose special anchors and wall plugs to break thermal bridges — for example, TherMax,” adds Býma.

If you can, opt for flush mounting

For new buildings or when completely renovating a house including the façade, it is best to install external blinds under the plaster, where no anchoring into the thermal insulation is needed at all. At NEVA we offer the ISO-KASTL Purenit box for these cases, which is anchored on the rough construction (without the façade) into the masonry above the window and then the façade builders cover it with at least 2cm of insulation. Purenit itself insulates well. Similarly, for the side guide profiles, we manufacture ISO-PANEL — an insulating board that you anchor into the masonry with an L‑profile, the façade builders fix it and then the company just pushes the guide rails into it when installing the blinds.

In any case, anchoring external blinds into the façade is not a major problem from an insulation point of view. What is more critical in this respect is the strength of the façade — how well the anchors hold in it. Therefore, in the case of a visible installation, ideally have everything anchored into the window frame or the front of the façade so that the anchors reach the underlying masonry with a margin.

For more information on how to anchor external blinds, please contact our sales and installation partners.


Lukáš Musil

Lukáš Musil has worked in NEVA as a business representative for the Czech Republic since 2017. He studied building construction at the Secondary Technical School in Prostějov and still uses the knowledge acquired in this field. He is in charge of customer care and communication.

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