Scientific research underlines effectiveness of internal solar shading

In daily practice, external blinds are usually considered the best and most effective option, but does that statement still hold true in 2022? The answer to this is short and to the point: no. Various scientific studies have proven that internal blinds with smart control can be as effective. The latest BENG requirements also endorse the effectiveness of functional internal solar blinds.


  • 3 May 2022

"In the last decade there has been a huge development in the field of glass and interior blinds. A carefully selected combination of these can be just as efficient as outdoor shading." That statement is made by Max Tilberg, CEO of EQUA Solutions AB, a Swedish company that develops software for simulations in construction. ESBO is considered the number one tool for the first performance explorations by means of simulation of energy and the indoor climate and especially based on the building envelope, the facade. ESBO can also be used to simulate the use of dynamic shading (inside or outside) according to established standards.

Simulation software

According to Tilberg, the most efficient solution for an optimal indoor climate is to combine the use of highly selective, low-reflection glass coatings with highly reflective interior sunshades. In his view, the screen in question consists of an aluminiumized front which can reflect more than 70% of solar radiation more or less independently of the colour of the back. In the case of triple glazing, this combination of coatings and internal blinds can even reduce solar heat gain by more than 85%. He also notes that, in this case, more than 60% of daylight still passes through. Internal shading also acts as an excellent glare protection and can reduce heat loss/U-value by about 10%. Due to the aluminium coating, the internal blinds provide a good view of the outside. And finally: compared to outdoor sun protection, indoor sun protection does not need to contain PVC for its functional aspect. Using a simulation tool such as ESBO, the visual and thermal performance can be easily calculated.


The calculation model of Samuel de Vries, PhD student at the Technical University of Eindhoven, also shows that internal blinds can be a very good alternative to external blinds, provided that it is included in the building concept. In his own words, this is a break with the general thinking in architecture courses, where the focus is almost exclusively on external blinds. One of the conclusions even states that there are situations in which dynamically controlled indoor sun protection can be more effective than outdoor sun protection if you consider all aspects, such as insulation values and visual comfort. Indoor solar shading leaves room for better tuning, even making it possible to work with daylight all day long. Also Lindsay Hovenier

Verosol agrees and said: "In addition to outdoor sun protection, brightness protection is often needed, but with the right coordination in the indoor sun protection, one product is all you need."


The use of functional internal blinds as an alternative to external blinds offers nothing but benefits, especially in utilities and high-rise buildings, concludes Hovenier. "The facade can often be made cheaper and lighter, and you don't have to worry about the maintenance of the sun blinds. Metallised internal blinds combined with double glazing (instead of triple glazing) mean that in winter you can harvest the sun during the day, and keep the heat in longer by lowering the internal blinds after the sun goes down, thus reducing the need for heating. A win-win." Functional internal blinds that are an integral part of the building control system may be included for both insulation and solar control according to BENG requirements. Although the NTA 8800 as an underlay for the BENG will soon be amended to some extent, the section on sun blinds remains unaffected. "Indoor sun protection is therefore not only a scientifically proven alternative to outdoor sun protection, it is also endorsed by legislation and regulations."