Slats, materials and performance · Rolling Shutter Guide
Do rolling shutters black out a room completely?
Yes, when fully closed. On insulated slats, small vent slots let light and air through while the curtain hangs partway down, but once it reaches the bottom the slats close up on each other for total blackout. For darkness at every position, order the non-vented 38 mm slat; the perforated slat never blacks out.
Key facts
- Fully closed, Roll-A-Shield's vented insulated slats close up on each other and block all light and most rain. Roll-A-Shield data
- Venting is standard on both insulated slats; the 38 mm slat can be ordered non-vented, the 55 mm slat is made vented only, and the 63 mm single-wall slat cannot be vented. Roll-A-Shield data
- On a vented 38 mm shutter the top 3 slats are built without vent slots, so the top does not leak light if the curtain is not pressed all the way down. Roll-A-Shield data
- Spring-operated shutters come non-vented, because a spring can lift a closed curtain slightly and open small gaps. Roll-A-Shield data
- The perforated 63 mm slat lets light through at all times, even fully closed. Roll-A-Shield data
Applies to: Rolling shutters with Roll-A-Shield's 38 mm and 55 mm insulated slats (vented or non-vented) and 63 mm single-wall solid and perforated slats, any operator.
A fully closed rolling shutter gives total blackout: the aluminum curtain closes up outside the glass and lets no light in. The detail that surprises people is venting: Roll-A-Shield's insulated slats come vented as standard, so they let light through while the shutter is partway down. This page explains how that works, which slat to choose for a dark room, and what to check if light still gets in.
Will a rolling shutter make a room completely dark?
Yes, when it is fully closed. As the curtain reaches the bottom, gravity pulls the slats into each other and closes them up, which blocks the light and keeps most rain and weather out. The bottom slat carries a rubber weather seal that presses on the sill, floor or threshold, sealing the bottom edge against light and drafts.
Why does light come through when the shutter is partway down?
Because of the vent slots. On Roll-A-Shield's insulated slats, a dashed line of small slots is punched in the hinge of each slat. While the curtain hangs partway down, the hinges are open and the slots let light and a breeze through; you can stop the shutter at any height for partial light and visibility. Once it closes fully the slots are covered and the room goes dark.
| Slat | Venting | Dark when fully closed? | Dark when partway down? |
|---|---|---|---|
| 38 mm insulated, vented (standard) | Vent slots; top 3 slats solid | Yes | No, light through the slots |
| 38 mm insulated, non-vented | None | Yes | Yes, apart from the open space below the curtain |
| 55 mm insulated | Always vented | Yes | No, light through the slots |
| 63 mm single-wall, solid | Cannot be vented | Yes | Yes, apart from the open space below the curtain |
| 63 mm perforated | Holes stay open | No | No |
Two build details matter for a dark room. On a vented 38 mm shutter, the top 3 slats are built without vent slots by default, so the top of the curtain does not leak light if it is not pressed all the way down. And spring-operated shutters come non-vented, because a spring can lift a closed curtain slightly and open small gaps between the slats.
Which shutter is best for a bedroom, home theatre or day sleeper?
Any insulated-slat shutter gives blackout when it is fully closed. If you want the room dark at every position, order the non-vented 38 mm slat. Two more choices help:
- U-channel at the bottom. A U-channel is fitted where the curtain has no flat surface to land on, or for additional room darkening. See Do I need a U-channel?
- Avoid the perforated slat. It is made for seeing through a closed shutter and never goes dark.
Why does light still show around my closed shutter?
Check whether the curtain has closed fully, and whether it is too long for the opening. Work through this table:
| Symptom | Likely cause | What to do |
|---|---|---|
| Light through the slots across the curtain | The shutter stopped short of the bottom, so the vent slots are still open | Run it fully down; if a motor stops short every time, reset the lower limit: stops too high or too low |
| Thin lines of light at the top slats, sometimes with banging | Curtain too tall for the opening, so the top slats come down at an angle and do not settle | See light gaps at the top |
| Light along the bottom edge | No flat surface for the bottom slat to rest and seal on | Ask about a U-channel, which is fitted where there is no flat resting surface or for extra room darkening |
| Light through holes in every slat | Perforated slat, which is designed to let light through | Expected; a different slat would be needed for blackout |
Does blackout also block heat?
It helps: a fully closed shutter stops direct sun reaching the glass, and the insulated slats slow heat transfer. The tested insulation figures are on Do rolling shutters insulate?.
What next
If you are ordering for a dark room, say so on the quote and we will specify the slat and bottom detail. Call (480) 921-0200 or request a quote.
Watch it done
Vented and non-vented slats: light partway down, blackout when closed
The written steps on this page are the reference; the video shows the same job.
Frequently asked questions
Will a rolling shutter work for a day sleeper or night-shift worker?
Yes. A fully closed insulated-slat shutter blocks all light. If you also want the room dark with the shutter partly open, order the non-vented 38 mm slat.
Can I get light in during the day and full dark at night with one shutter?
Yes, that is what the standard vented slat does: stop it partway down for light and a breeze, close it fully for blackout.
Why is there a line of light at the top of my closed shutter?
One known cause is a curtain that is too tall for the opening: the top slats come down at an angle and do not settle, leaving thin lines of light. It has its own fix; see the page on light gaps at the top.
Can I see out through a closed rolling shutter?
Not through a solid or vented slat. If you want to see out while it is closed, the perforated 63 mm slat is made for that, and it does not black out.
Parts and next step
Need a part or a hand?
For a bedroom, home theatre or day sleeper, ask for a non-vented 38 mm slat and a U-channel at the bottom, and tell us how you want the room in daytime. Call (480) 921-0200; the factory answers technical questions for any rolling shutter, not only ours.