What is the most efficient way in which you can darken your windows? External blinds and blackout roller blinds are the ones to go for
Some blinds, curtains or roller blinds have such great darkening ability that they will make your room almost absolutely dark even during the day. You will appreciate that if you want to catch up on your sleep during the day following night shifts or, for example, you use a projector instead a TV set. In addition to the darkening ability, however, also take account of further properties of shading including, among others, the possibility of controlling light because of indoor plants.
The most popular option of shading in Czech households is internal blinds (horizontal or vertical), textile screens, pleated blinds or curtains. Curtains may create slight gloom in the room when drawn, but that does not compare to absolute darkness. Various films intended for glass, which protect your privacy but cannot darken the room efficiently, have similar effects.
Internal blackout roller blinds and curtains darken the room very effectively but warm it up as well
In terms of darkening of windows, internal roller blinds, Roman roller blinds or curtains made of blackout fabric are much more efficient. Blackout fabric is extremely dark with zero light transmittance that forms an impenetrable barrier when drawn.
However, we are still talking about internal shading in which a bit of light shines through onto the sides or from the ceiling. You can minimise that by choosing curtains with a sufficient overlap on both sides so that you can cover the entire window opening with enough reserve. Similarly, you can buy roller blinds with side rails that minimise light shining through the sides.
The great weakness of internal blackout roller blinds or curtains is their thermal properties, though. Especially on hot summer days, when you have the sun beating down on the windows, the black fabric becomes a radiator that emits heat around the room. That is why we recommend buying an air-conditioning system in this case so that you do not fry in the room.
Unfortunately, you also do not have the option to control light with blackout curtains or roller blinds – you can only draw them down or up. That is not good for indoor plants. Based on our experience, similar shading is suitable, for example, for the bedroom where you only sleep, but, on the contrary, unsuitable for common rooms such as the kitchen or living room, where you spend time with your family and you simply need to occasionally have some shade.
Day and night roller blinds have been gaining popularity in recent years as well. They are composed of two layers of fabric, with each layer having alternately translucent and non-translucent stripes on it. By overlapping the stripes gradually, you can control light and you will darken the room more effectively than, for example, with classic internal blinds. On the other hand, day and night roller blinds do not darken the room so well as smooth blackout roller blinds because the layers do not fit to one another so much and some light penetrates between them.
External blinds: they darken the room well and work as an insulator
External blinds have very good darkening abilities, too. In particular, those with Z or S slats that completely close when drawn down, i.e. “lock” to form a smooth surface. Although there are slots in the slats for the lift tape and the blind do not completely fill in the guide profile, you will most probably be pleasantly surprised by their darkening ability. Once they are drawn down, there is almost complete darkness in the room.
In addition, there are special blackout external blinds in the market that have openings in the slats designed in such a way to prevent any light shining through them at all. Blackout blinds are more of a specialty item in both the Czech and global markets, though.
Compared to roller blinds or curtains, external blinds allow much more flexible control of light, when by tilting the slats you can create anything from complete light to nearly absolute darkness in the room. They also work as a thermal insulator that deflects most of the heat hitting the window and does not let it into the house at all. What’s more, we have tested them and found that they have very good sound insulation properties as well.
How external blinds can decrease the temperature in the room
For the reasons mentioned above, external blinds represent a reasonable compromise between the amount of darkening and the ability to control light. By contrast, the disadvantage of external blinds is their higher price and the necessity to pull them up in strong wind or heavy rain.
External roller shutters: great variability of darkening thanks to the fabrics
External roller shutters are divided into classic external roller shutters made of aluminium and external textile screens.
Aluminium roller shutters have very similar properties to the external blinds described above, with the only difference being that they do not allow such flexible light control. All you can do is pull them up or down. As they are made up of one smooth part, they provide an even better impression of darkness. Nevertheless, the difference when compared to external blinds (and, in particular, to Z or S slats) is minimal.
The darkening ability of screens is determined by the fabric from which they are made. There are translucent, slightly darkening or completely darkening fabrics. Fabrics that provide the most effective darkening and 0% light transmittance are called blackout fabrics, similarly as in the case of internal shading.
A screen made from blackout fabric is the most efficient solution in terms of darkening the room. A bit of light only shines through the sides in the construction opening; otherwise, you have absolute darkness in the room. However, we again draw your attention to the limited flexibility of light control, which is why we do not recommend this solution so much for common areas such as the living room. A slightly darkening roller blind or external blind are much more suitable for the living room.