How to insulate windows against sun and heat

insulate windows against sun and heat

What are the best ways to insulate windows against sun and heat? Our guide outlines the 7 top ways and the pros and cons of each method.

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If it’s hot outside and you want to stay cool inside, you need sun protection for windows. But what works best?

Temperatures around 30 degrees, are a dream for every sun worshiper. If you can, you can enjoy the hot summer outdoors and cool off in the outdoor pool or at the lake. Unfortunately, the apartment or house heats up so much during the day that staying in it can become unbearable. The best thing to do is to ensure that the heat stays outside with the right sun protection, along with protection against ultraviolet (UV) rays.

Best ways to insulate windows against sun and heat

Thermal insulation and window glazing

If you are a future homeowner, you should already think about appropriate heat protection during the construction phase. Modern houses are now directly equipped with appropriate thermal insulation. This “insulating layer” ensures that the house does not heat up so quickly and stays pleasantly warm in winter.

The same applies to the window glazing, because the windows let through most of the sunlight and thus the heat. When it comes to a new building, it is best to seek advice, because there are many possibilities today to install energy-saving and heat-absorbing windows. 

Sun protection glass with a metal coating that lowers the temperatures in summer and provides better thermal insulation in winter has proven to be very effective. Don’t worry, the metal coating is invisible and does not impair the incidence of light.

Sliding panel curtains – individual heat protection

Curtains are the classic against too much heat in the house or apartment. Unfortunately, “normal” curtains only help to a limited extent in keeping the heat outside. The fabrics are usually intended as window decorations or privacy screens – these fabrics do not have any special anti-heat properties.

Sliding curtains, which consist of several narrow, smoothly falling lengths of fabric and which can be pushed in front of the window exactly where you would most like to have them, offer significantly more effective sun protection. Thanks to the simple suspension in the so-called panel trolley, several lengths of fabric can be pushed one on top of the other. Sliding curtains are made from different fabrics. The best results are offered by opaque sliding curtains as sun protection . If they are also coated with reflective aluminum on the back, they ensure that the apartment stays nice and cool.

Window film – quick DIY sun protection

insulate windows against sun and heat

You will probably be familiar with window film or sun protection film from many cars. The rear panels are more and more often provided with dark foil, on the one hand to protect the interior of the car from prying eyes, and on the other hand to keep the car cool in extreme heat.
This principle also applies to all types of windows. The foils are self-adhesive and can easily be attached by yourself. Sun protection film with reflections not only keeps out heat, but also provides good privacy. The disadvantage, however, is that the film also darkens the room in winter.

Darkening with external blinds

One or more external blinds can hold off up to 75 percent heat. It is best to let them down in the morning so that the sun has no chance to heat the rooms. Small disadvantage: If you stay in the house all day, you have to spend it in the dark. The blinds should only be raised once the sun has set and the air outside has cooled down a bit.

»Note: External blinds can be retrofitted, but never without the consent of the landlord.

Inner blind and pleated blind

insulate windows against sun and heat

Roller blinds and pleated blinds installed inside can also provide excellent protection against too much heat from solar radiation. But only if you rely on heat-resistant thermal blinds and pleated blinds (especially mother-of-pearl and honeycomb pleated blinds). These are provided with a so-called Perlex coating that can reflect thermal radiation and light. Honeycomb pleated blinds are made up of honeycomb-shaped tubes and thus contribute to insulation.

Conventional pleated blinds or roller blinds that are transparent, on the other hand, only protect rooms to a very limited extent against the effects of summer heat.

Awning – large area shade provider

insulate windows against sun and heat

First and foremost, sun protection for houses and apartments is of course about shading the windows. The less they are exposed to direct sunlight, the better. Awnings are not only ideal for this, the extendable lengths of fabric also protect balconies and terraces from the sun. In the case of single-glazed windows, however, it should be remembered that the heat can “pull” into the house even in the shade. The same applies here: Attaching an awning requires the consent of the landlord!