Category Archives: Product Choices

Roof Blinds for Skylight Windows

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With work on the Outbuildings progressing, it will only be a few months until those provide a large Workshop space which will replace the current use of Bedroom 5 on the Second Floor of the House, which has been temporarily acting as a workshop and ‘shed’. It’s therefore a good time to start preparing for that being used as a bedroom; up until recently little had been done since it was first built and the walls and ceiling were still bare plaster.

Natural lighting for Bedroom 5 comes from two fixed skylight windows deeply recessed into the ceiling which slopes at 11 degrees to the horizontal. They’re tilted towards the North but with them being so nearly horizontal they do receive direct sunlight in the summer months, which can tend to make this room a bit too warm. These windows therefore want ‘blackout’ blinds which exclude enough light for sleeping in this bedroom and which can also be used to block out the summer sun.

Many of the available skylight blinds are designed to be fitted to the wooden frame of opening roof windows from VELUX and similar window manufacturers, where the blind needs to move with the window when that opens and closes. Those are a good solution where the window opens and where they are relatively accessible – such as in a loft conversion. However, they’re not suitable for this installation.

As with all the other ‘windows’ in the House, these skylight locations were wired back to KNX-managed relay controls for 230V electric blind motors, using three-core-and-earth cabling. All but one of the other windows have electric roller blinds (the exception has an electric vertical blind) which rely on gravity and a metal hem bar to operate. With these windows being so close to horizontal, roller blinds need ‘help’ to close – and to stop them sagging.

Previous research to find suitable blinds had failed to identify a good solution. The closest match is blind systems used for genuinely-horizontal ‘roof lights’ or ‘roof lanterns’. Some roof light blinds use ‘honeycomb’ fabric and low-voltage motors and radio controls, which would complicate the automation compared with a simple 230V motor and relay control. Other systems designed for (much) larger roof lanterns had minimum sizes which were slightly too large for these relatively modest skylight openings.

In the end I settled on the Helios RL Wire-guided rooflight system from Umbra Shading for which there is a good range of technical resources explaining how they work. In broad terms, these use spring-loaded wire spools to apply tension to the blind fabric and to pull it down as the motor unwinds. Local installer Butterley Barn Interiors supplied and installed Helios RL blinds with enclosed top and bottom boxes to conceal the roller tube and spring boxes.

Umbra Shading Helios RL blind in sloping ceiling of Bedroom 5

There’s a bit of a gap at each side of the blind, where the guide wires are. For an even better blackout effect that could be covered with an angle-section trim strip

Dimmable LED Bulb Experiences

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LED lighting has definitely come of age and all of the lighting in the property uses LED technology. Where the lights are purely functional (e.g. the outdoor floodlights) or offer low-intensity feature lighting the fittings are simply switched with a relay but most of the internal lighting is controlled via dimmers.

In general, the dimmable light fittings have embedded LEDs for the actual light output and separate LED drivers (i.e. control electronics) – typically mounted remotely. These all work very well and offer great dimming performance using DALI control. DALI is a a great way to control lighting dimmers – a digital signal is transmitted over a dedicated control bus directly to the LED driver which then sends the appropriate low-voltage waveform to the LED itself.

There are a handful of exceptions:

  • The outdoor light on the balcony is a Nordlux Canto Maxi which takes 2 x GU10 bulbs. While this is installed on the balcony it’s close to the big sliding glass door into the main bedroom and hence it effectively counts as one of the bedroom lights and deserves to be dimmable.
  • Some of the bedrooms and living rooms are wired for dimmable bedside or table lamps, controlled together in sets. (These are connected via round-pin 5A sockets to prevent other appliances being connected by mistake.)

Dimming for these circuits is via Aurora AU-DATR400 dimmer units which take a DALI signal and generate a “dimmed” mains waveform. It should be a simple case of installing a dimmable LED bulb into the light fitting.

The only big disappointment with the lighting control on the whole project was with the GU10 bulbs for the balcony light. Recognising that dimmable LEDs are still problematic it seemed sensible to stick with the big brands so I opted for some Sylvania GU10 bulbs which appeared to be high-quality (made in Belgium) but which did not perform at all well. The main issue was that the light level would oscillate between the two bulbs a few times a second. They were OK at near full brightness but dimming was a disaster.

Lesson learned and with more caution I waited a few months before looking for dimmable bulbs for some bedside lights. These were going to be very visible within their light fittings and I settled on some golf-ball-style bulbs from Philips Lighting, with their “warm glow” feature (where they dim to a lower colour temperature):

These worked perfectly and look good. Dimming performance is excellent. I still can’t get used to the fact that they don’t even get warm.

I then decided to try swapping the GU10 bulbs in the balcony light for Philips units with equal success.

Conclusion: I’m going to be buying dimmable LED bulbs from Philips from now on.

Different brands and models of LED bulbs react in different ways and the control technology is still developing rapidly so where multiple dimmable LED bulbs are installed on the same circuit (e.g. several table lamps in a living room) it’s likely to be necessary to buy and replace bulbs in batches – same manufacturer, same model, bought at the same time.