Same blind, same window, same fabric — and a completely different result, simply because one window faces south and the other faces west. That is the most common reason an investor says "something is wrong" at the end of a project, even though every product is individually correct. The product is not wrong; it has been distributed across the façades wrongly.
This guide is written for specifiers, contractors and blind retailers who specify sun protection for a whole building. We do not measure or install — we manufacture to the dimensions the partner sends — but that is exactly why we see, every day, which combinations work and which come back as a complaint that is not really a complaint.
Why the same blind does not do the same job on every façade
The sun does not strike every side of a building at the same angle, nor at the same time of day. Three things change from façade to façade, and each of them calls for a different answer:
- Sun altitude. On the south the sun is high — in summer at midday it falls almost from directly above. On the east and west it is low, because it arrives at sunrise and sunset. Low sun reaches deep into the room and cannot be stopped by anything mounted above the window.
- Duration. The south façade is sunlit longest, but most evenly. East and west receive a shorter but more intense hit — east in the morning, west in the afternoon, when the air is already warm.
- What the actual problem is. On the south the problem is heat. On the east and west it is glare. On the north there is neither, so what remains is privacy and appearance.
A simple rule follows: the system is chosen for the problem the façade creates, not from the catalogue. Skip that rule and you get a building with the same blind everywhere — overheated on one side, dark on another, and on the third nobody can see their screen at three in the afternoon.
A note on orientation: everything in this article applies to the northern hemisphere. If the project is for a market south of the equator, south and north swap roles, while east and west stay the same.
South — the most heat, external shading comes first
The south façade receives the largest amount of solar energy over the year. In summer that is a problem measured in kilowatts of air conditioning; in winter — paradoxically — an advantage, because the low winter sun heats the rooms for free. A good system for the south has to do both: block the heat in summer and let it through in winter.
The key question is where the heat is stopped. An internal blind stops light, but the heat has already passed through the glass and stays in the room. An external blind stops the sun before the glass, so the room never heats up in the first place. The difference is not cosmetic — in practice it decides whether the air conditioning runs or not.
ZIP screen system
The first choice for the south on commercial and residential buildings. Screen fabric in side guides stops most of the solar energy before the glass while keeping the view out. Thanks to the guides it copes with wind, which on the outside of a building is mandatory, not optional. The savings on air conditioning are covered in a separate article.
Pergola over a terrace or garden
For south-facing terraces, restaurant gardens and hotel outdoor areas. A bioclimatic pergola with rotating louvres closes the roof in summer and opens it in the shoulder seasons — doing exactly what a south side asks for: variable protection.
Internal roller blind with screen fabric
When external mounting is not possible (a listed façade, leased premises, upper floors without access), an internal roller blind with sun screen fabric is a sensible substitute. It stops glare and part of the heat, but be honest with the investor: it cannot replace external shading when it comes to overheating.
East and west — low sun and glare
The east and west façades share the same problem at different times of day: the sun is low, enters horizontally and lands directly on screens, desks and faces. Nothing mounted above the window — a canopy, a brise-soleil, a pergola — helps, because the sun is not coming from above but from the side.
Of the two, west is harder. Afternoon sun hits a façade that is already warm and a room whose air has been collecting heat all day. West-facing offices are where the complaint "I can't see my monitor after three" is most common — and that is a complaint about glare, not about temperature.
Zebra (day-night) blinds
The most flexible internal answer for east and west. The alternating bands shift so that the space can be closed at three in the afternoon and opened again at half past four — without total darkness. For offices and meeting rooms on the west side this is the type that comes back least often.
Roller blind with sun screen fabric
When the priority is keeping the view and daylight. Screen fabric lets outlines through from outside but cuts glare to a level that allows computer work. The degree of shading is chosen for the room's use — we have written separately about fabric types.
External ZIP system
When a west façade has a heat problem as well as glare — large glazed areas, glazed halls, offices under a flat roof. The guides let it stay down even when the wind picks up, which is common on open sites in the afternoon.
A mistake that keeps recurring: blackout fabric in west-facing offices. It solves the glare, but creates darkness in the middle of the working day, so people switch the lights on and raise the blind — and are back where they started. Blackout belongs in bedrooms and hotel rooms, not in workspaces.
North — no direct sun, privacy and appearance remain
For most of the year the north façade receives no direct sun, only diffuse light. That is the best light to work in — even, without shadows and without glare — and it would be a shame to close it off with a heavy fabric.
What the north asks for is privacy (especially on the ground and lower floors), screening from view in the evening when the lights are on inside, and visual consistency with the rest of the building. Heat is not an issue, so external shading is rarely justified here.
- Roller blind with a lighter decorative or screen fabric — enough screening from view, minimal loss of light.
- Zebra blinds — when the room has a mixed use and occasionally needs closing.
- Venetian blinds — when the priority is the look of the interior rather than performance; on the north they do not risk fading or overheated slats.
The only exception is a north façade with large glazed areas in a cold climate, where the fabric serves at night as an extra thermal layer — there a denser fabric makes sense, but for the opposite reason than on the south.
Table: façade, problem, system
This is a starting point for the specification, not a finished answer. Every project has its exceptions — neighbouring buildings casting shade, trees, canopies — but as a first filter the table saves time.
| Façade | Main problem | First choice | Internal alternative |
|---|---|---|---|
| South | Heat, overheating | External ZIP screen; pergola over the terrace | Roller blind with sun screen fabric |
| East | Morning glare | Zebra or screen roller internally | External ZIP if heat is also an issue |
| West | Afternoon glare + heat | External ZIP on large glazing; zebra internally | Roller blind with a denser screen fabric |
| North | Privacy, appearance | Roller blind with a light fabric; venetians | Zebra for mixed use |
Combining external and internal protection
On more demanding buildings the best result comes not from one system but from two layers: external for heat and internal for light and privacy. An external ZIP screen cuts overheating, while a roller or zebra blind inside gives the user the control an external system cannot — closing off from view in the evening, or darkening a projection room.
Two layers do not mean double the cost across the whole building. The practical rule is: external shading only where heat is the problem (south, possibly west), internal everywhere. That way the more expensive system goes on a third of the façade, not all of it.
For the specifier this means the specification is written by façade, not by room type. Two identical offices, one on the south and one on the north, get different systems — and that is correct, not inconsistent.
A quotation by façade, not by catalogue
We work exclusively with businesses — specifiers, contractors and blind retailers. Send a measuring sheet with the orientation of each position and receive a proposal of systems by façade, with fabric samples.
Send an enquiry →What a partner sends us with an enquiry for a whole building
To propose systems by façade instead of one blind for everything, we need three more pieces of data per position alongside the measuring sheet. None of them requires an extra site visit — all of it can be read from the drawings:
- Orientation of each position — a simple S / E / W / N mark next to the dimension is enough.
- Floor and whether external mounting is possible — whether the façade allows guides and a cassette, and whether there is access for installation.
- Use of the room — office, meeting room, hotel room, restaurant. The same west façade needs a different fabric for a hall than for a bedroom.
With those three pieces of data we prepare a quotation by façade, with fabric samples for each group. Samples are sent to partners free of charge — the colour and openness of a screen fabric on a monitor and in the light of a south-facing window are not the same thing.
Frequently asked questions
Which sun protection system is best for a south façade?
An external ZIP screen system, because it stops solar heat before the glass. For south-facing terraces and gardens — a bioclimatic pergola. An internal roller blind with sun screen fabric is a substitute when external mounting is not possible, but it does not deal with overheating as well.
Why does a pergola or canopy not help on a west-facing window?
Because afternoon sun on the west comes in low, almost horizontally, not from above. Anything mounted above the window does not stop it. West needs protection in the plane of the window: zebra or screen roller blinds inside, ZIP outside.
Is blackout fabric a good choice for west-facing offices?
No. It solves the glare but creates total darkness during working hours, so artificial light goes on and the blind goes up. Workspaces take screen and zebra fabrics; blackout is for bedrooms and hotel rooms.
Is external shading needed on a north façade too?
Usually not. North has no direct sun and no heat problem, so an external system has nothing to stop. On the north, lighter fabrics are chosen for privacy and appearance, with as little loss of diffuse light as possible.
What should I send with the measuring sheet to get a quotation by façade?
With each position's dimensions: its orientation (S/E/W/N), the floor with a note on whether external mounting is possible, and the use of the room. All of it can be read from the drawings, without a site visit. On that basis we send a quotation by façade and fabric samples.
Conclusion
Sun protection is not one product but an answer to three different problems — heat, glare and privacy — which appear on different sides of the same building. South needs external shading, east and west need control of low sun, north needs only screening and appearance.
A building where that has been respected can be recognised by one thing: nobody notices the blinds. They do their job, the air conditioning does not struggle, the screens are readable. And for the specifier and the investor, that is the only result that counts.