The mechanics of a zip screen are the same in every application: the fabric edges lock into a zip strip running in the side tracks, so it cannot be whipped about by wind and no gaps remain at the sides. What distinguishes one system from another is not the mechanism but the fabric fitted into it. On the same cassette and tracks you can use screen, crystal PVC or blackout; the space that results is entirely different. In this article we compare the three fabric types on view, privacy, wind and heat.
Screen fabric is the most common choice in zip screen systems. It is woven from PVC-coated yarns over a glass fibre or polyester core and has a certain openness factor. That factor is the ratio of the gaps in the weave to the total surface, and it is the single number defining the fabric's character. Screen does not close; it filters. It cuts the sun's direct rays while letting a degree of view and air through.
As the openness factor drops the fabric tightens. A tight weave cuts more sun, increases privacy and lets less heat through; in return it blurs the view. As the factor rises you see out more clearly but sun control weakens. On a terrace with a Bosphorus view a factor preserving the view is right; on a west-facing café façade, a tighter factor cutting the afternoon sun.
The most commonly misunderstood property of screen fabric is that privacy is one-way and depends on daylight. During the day it is brighter outside than in; someone outside cannot see in, while you see out. When you turn lights on inside in the evening the relationship reverses: now it is brighter inside and the interior becomes visible from outside. For a terrace used heavily in the evening, screen alone is not a privacy solution.
Because screen lets air through, air is not trapped underneath. If you do not want the terrace turning into a fully closed box, that is a significant advantage. The same property limits protection from rain: screen lets water through. It largely blocks wind-driven rain but is not a surface that stops rain entirely. If full rain protection is expected, crystal PVC is required.
Crystal PVC is the transparent option in a zip screen. Rather than a weave, a single-piece transparent PVC film is used. The surface is non-porous; it passes neither water nor wind. On café and restaurant terraces this is the most practical way of continuing use through winter: view and light are preserved while cold air and rain stay outside. It is a seasonal solution at far lower cost than glass systems.
Crystal PVC also has limits worth knowing. The transparent film can yellow over time and is not as scratch-resistant as glass; hard cloths and abrasive products must not be used in cleaning. And because it is non-porous it does not breathe at all: moisture can build up inside and condensation forms on the surface on cold days. Ventilation needs must be planned for closed use.
Heat behaviour also differs with crystal PVC. The transparent surface admits most of the sun's radiation; in winter that is an advantage, as the interior warms on a sunny day. In summer the same property becomes a disadvantage, as a greenhouse effect builds under a closed transparent surface. Planning crystal PVC as a seasonal solution alongside screen is therefore the soundest setup.
Blackout fabric is the third option and its purpose is entirely different: to stop light. The fabric is produced with a light-blocking layer; lowered, it darkens the area and provides complete privacy. View is zero. Unlike screen and crystal PVC, this is a choice that deliberately cuts the relationship with outside.
Blackout's natural field of use is where darkening rather than view is wanted. A narrow terrace facing a neighbouring balcony, a garden corner at street level, an outdoor seating area using a projector, or a section meant for daytime rest. It also suits a section of a hotel terrace where darkening is wanted in the middle of the day.
Blackout is strong on heat control because it cuts all the sun's radiation; the surface behind it does not warm. Against that, the fabric itself warms and can radiate that heat inwards. A light-coloured blackout fabric reduces this effect because it reflects light back off the surface. Choosing a dark colour gives stronger darkening but the fabric surface warms more.
Against wind all three fabrics work on the same mechanical logic: because the zip system holds the edges in the tracks, the fabric cannot come out at the sides. The difference lies in the surface the fabric presents to the wind. Screen lets some of the wind through via the weave openness and the pressure on it stays lower. Crystal PVC and blackout are closed surfaces and meet the whole of the wind; across wide openings that affects cassette and track selection.
Maintenance requirements differ too. Screen fabric is cleaned with a soft brush and soapy water; low-pressure clean water is enough for dust lodged in the weave. Crystal PVC must be wiped only with a soft cloth and plenty of water, and never dry-wiped; dry wiping creates a web of scratches on the surface and dulls its transparency. On blackout fabric, hard brushes and solvents must be avoided so the light-blocking layer is not damaged.
In practice a single fabric type rarely suffices on a project. The common solution is to divide the façade by how it is used: screen on the main opening facing the view, crystal PVC on the side façade exposed to wind and rain, blackout on the narrow edge facing the neighbour. When different fabrics are used on the same system the cassette and track appearance stays identical; seen from outside, the coherence is not broken. We covered ceiling applications separately on our ceiling zip screen page.
In summary: if you want to cut sun while keeping the relationship with outside, screen; if you want to stop rain and wind entirely and continue use through winter, crystal PVC; if you want complete darkening and privacy, blackout is the right choice. The decision comes from assessing the façade's orientation, view expectation, which seasons see the heaviest use and the share of evening use together. We covered wind and sun control in this article, and fabric technology in our fabric selection article.
To determine the right fabric type for each part of your façade, request a free site survey.
Frequently Asked Questions
By day yes, in the evening no. During the day it is brighter outside so the interior cannot be seen from outside; when lights go on inside in the evening the relationship reverses and the interior becomes visible.
It can, but it is not recommended. A transparent closed surface admits the sun's radiation and builds a greenhouse effect. Planning crystal PVC as a seasonal solution alongside screen is sounder.
Yes, it is a common solution. Screen on the opening facing the view, crystal PVC on the wind-exposed edge and blackout on the section facing the neighbour; the cassette and track appearance stays the same.
