Internal vs External Shading: Which is a better choice?
Unprotected glass is the greatest source of heat entering a building. As temperatures continue to rise, in part thanks to global warming, keeping your home cool and comfortable can seem challenging.
According to the Big Issue around 20 per cent of homes in England alone overheat in the summer and a drive to insulate homes against cold could make overheating even worse.
Roller blinds are a popular choice for anyone trying to reduce glare & overheating, provide privacy or create total blackout in their homes.
As the name suggests, internal roller blinds are fitted inside the home. They can be fixed within a window reveal or face fixed to the outside of the window, depending on the space available.
When it comes to the types of roller blinds available, there are two main categories to choose from: internal and external shading.
External roller blinds however are fitted to the outside wall or roof of the home and cover the window from the outside.
Choosing the right option for you will depend on what your priorities are. To help you decide, let’s discuss the benefits of both options.
Dynamic shading
The key thing to keep in mind about external shading is that it’s often fixed. This is because it’s much easier to install fixed shading to the outside of a building as it doesn’t need to be actuated by a person to open or close it.
What this means is that it’s only working to full effect when the sun is in the right position for the shading. As the sun moves throughout the day and the seasons, and hits the window at different angles, external shading might be less effective at blocking heat and glare.
It is possible to install dynamic shading externally, but it usually comes at a higher cost than fixed. Dynamic external shading i.e. shades that can move, will need to be motorised so they can be operated from inside the building, and will usually require extra components such as wind sensors to protect the shading from the elements.
Internal shading on the other hand is usually dynamic. This means it can be adjusted to be more open or closed throughout the day, depending on the angle of the sun, to give you more flexibility over the amount of light coming in. It’s much easier to control dynamic shading internally than it is externally because it’s much more accessible.
Internal shading can also be automated using a sunlight sensor to work even when you’re not home. These sensors are usually more affordable than the sensors you would use externally, and are often small, discreet and can be wirefree.
Sunlight sensors can detect when there is too much light coming in through the window that could raise internal temperatures or cause problems with glare. Once the sensors detect a temperature or light level that is outside your predetermined parameters, the system will send a message to activate the blinds.
Control options
Internal blinds can be operated in many ways depending on your goal. On roller blinds alone, the options for control type include;
- Chain
- Crank handle
- Hardwired switch
- Wireless switch
- Wireless remote control
- Smart Home system
- Sun sensor/timer
Even within the above categories, there are options from many different suppliers and manufacturers, all with their own unique benefits and features to suit your needs and preferences.
As we said earlier, external shading is either fixed (can’t be controlled) or it must be motorised so that you can control it from inside. A wind sensor is necessary because it prevents damage to your blind that can be caused if it’s left down during strong winds.
This isn’t ideal, though, because if you happen to have a day with strong wind and sunlight, which is not uncommon in Britain, your external shading won’t close to stop that light coming in because the wind sensor is preventing it from moving.
Maintenance
When it comes to maintenance, there are two factors to consider: the amount of maintenance you’ll need, and how difficult it is to maintain.
Internal roller blinds require very little maintenance. External shading is constantly exposed to the elements which can cause wear and tear over time, even if you’re careful not to use it during extreme weather. Just being installed outside, it’s going to be exposed to the elements 24/7. Especially during harsh British winters, this can lead to frequent maintenance issues.
Also, it might be difficult to access the windows to perform maintenance on external shading. On large buildings with high-level windows, accessing them to do maintenance on external blinds is going to involve the cost of access equipment and will need to be done by qualified professionals.
Performance
If you were to compare the shading performance of an external blind to an internal blind, at the same time of day and in the same window, the external blind will perform better. The reason for this is that an external shading system stops that heat and glare from hitting the window.
Here are some statistics from BBSA’s Solar Shading Impact Report (June 2016) comparing an external blind to an internal blind using a 10% openness screen fabric. The test was done on a standard double-glazed window and shows the percentage of heat transference through the glass.
| No shading | External Blind | Internal blind | |
| Double Clear (EN 14501) | 0.76 | 0.14 | 0.37 |
As you can see, the external blind only lets 14% of the heat through to the room, while the internal blind lets 37% through. This is because the external blind is stopping the heat before it gets to the glass.
Cost
Though external blinds will perform better, that comes at a price. External blinds tend to be more expensive than internal blinds as they’re manufactured to withstand the outside elements.
Installation also tends to cost more for external blinds as it takes longer, and if specialist access equipment is needed, that can add even more cost.
To get an idea of how much internal shading can cost, take a look at our latest RRP price list:
Conclusion
The decision between choosing internal or external blinds essentially comes down to this question: is the higher cost of external blinds justified by the performance?
In most cases, internal shading is more than adequate for the majority of property types. Even with the slightly less impressive performance, most people will find that the shades provide enough heat and glare control for their needs.