Heki Skylight Blinds

[Guest Mel E]

Our new van conversion has both a Seitz Heki Midi and a Mini. Both are fitted with concertina blinds which draw across (along the long side on the Midi) from one side to the other to darken the interior at night. Both have a huge problem: if the skylight is left even a little open (I like to breathe at night!), they rattle maddeningly in their draw-across slots in even the lightest of breezes, waking any lightish sleeper. This is, of course, because the slots have to be slightly wider than the concertina as it is obviously wider when closed than when fully open. The Mini Heki is especially noisy. When I specified Seitz, I had no idea of this design idiocy (it is quite clearly a design fault). Does anyone else have the same problem and, if so, have you worked out a fix?

[Guest bill h]

Hows about a large ring of say, wire or plastic like an oversize 'o'ring that is only just about flexible. Must be larger in diamater than the width of the opening. Spring it into place so it slots into the 'blind' channel for night use, remove at daylight. Works like a circlip. bill h

[Guest Derek Uzzell]

My Hobby has a 40cm x 40cm Remis roof-light and a 50cm x 50cm one, both with concertina blinds and 'permanent ventilation'. In very windy weather the drawn blind on the 40 x 40 rattles madly even when the roof-light is fully shut, but the blind on the bigger unit stays silent. The reason for the difference is undoubtedly because the former blind is loose in its guide slots, whereas the latter has 'guide strings' that run through the material and prevent it bouncing about. Not sure whether there's a certain solution, but you could try sticking some furry-backed, self-adhesive window draught-excluder strips in the guide channels. (Despite your criticism I still think the Seitz products are better designed than the Remis equivalents.)

[Guest Mel E]

I guess a wire like the Remis would help - if it is taught enough. The basic problem is Pythagoras! When the blind pleats are closed up, they need a space the width of the U-section channel. When open, each pleat is at an angle and hence the vertical component is less, allowing movement. Any permanent channel restrictor such as felt would stop the blinds drawing back. Any temporary restrictor such as Bill's suggestion, has to fit the whole length of the blind. The design solution is for the u-section to reduce in width as the blind engages at the drawn end - not a difficult thing to acvhieve. I am in contact with Seitz Germany's technical people and will let you know their response.

[Guest Derek Uzzell]

The Remis "strings" are literally that - pieces of man-made fibre string of the type used for bathroom-light pull-cords. They are under tension and presumably ensure the blind travels in a straight line and can't be accidentally pulled out of its guide slots. The fact that they discourage the blind from bouncing about within the slots is probably a handy bonus rather than a design feature. The Remis blind system on the interior side of the Hobby's living-area windows uses the same tensioned cord arrangement. I'm uncomfortably familiar with Pythagoras, having endured repeated school detentions as a result of persistent attempts by a mathematics master to force me to learn the proof of the famous Pythagorean Theory. Sadly all in vain, as, having grasped the practicalities of the 'square-of-the-hypotenuse' principle and realised that it had been used practically for several hundred years, I couldn't see why I should be bothered to prove the Theory was true because it clearly was. Surprisingly, mathematics was another of the many subjects I was destined never to excel at! I accept what you say about the possibility of the 'felt' inhibiting the retraction of a concertina blind. I had in mind that the draught-excluder stuff be stuck only along part of the length of the guide-slot (say from the middle to the 'fully closed' end) where the vertical dimension of the concertina material will be at its lowest. An alternative to draught-excluder would be the fuzzy 'eye' component of sticky-backed Velcro tape. Dunno if it would work to stop your rattles or whether there would be eventual wear problems, but it's a cheap enough experiment. As you rightly say, the elegant solution would be for the design of the roof-light to have incorporated a guide-slot with a profile tapering to match exactly the blind's reducing height when drawn. Not sure how easy this would be to do though unless Heki roof-lights are different to the Remis products, as the latter are fabricated from chopped off, short lengths of standardised extruded plastic with a constant cross section. It will be interesting to learn what Seitz say.

[Guest Brian Kirby]

Have you considered fully closing the rooflight above the bed, and only opening the more remote one for ventilation? You can then leave the blind open a bit too (flyscerrn closed), so that the air pressure fluctuations equalise through the ventilation gap, rather than rattling the blind up and down. The extra bit of light that creeps through the gap in in the mornings hasn't proved sufficient to disturb us. You also get a bit more ventilation because of the gapped blind, since I suspect precious little air does, in fact, pass around the fully closed blind (hence the rattles?). Ours has Remis rooflights, but they close fully and permanent ventilation is elsewhere. Derek may be able to add the edge seals to his to convert them. That might make the rattles manageable. Hope this helps Brian

[Guest Derek Uzzell]

Brian: Our Hobby's only high-level permanent ventilation is via the roof-lights, so having them sealed when closed would be inadvisable. The rattling is only apparent during high winds and partially opening the blind stops it. As neither of us need a fully darkened bedroom to be able to sleep, occasionally having a slightly open blind is no hardship for us.

[Guest Mel E]

Derek, I'm afraid your problems understanding Pythagoras betray you. When drawn right across, the blind has the same vertical component of height throughout its length and hence a rattle-stop-system would need to cover the entire length. As a bit of trivial pursuit, did you know that the square of the hypotenuse, etc., was actually defined by early mathematicians in what is now Iraq many hundred years before Pythagoras - he was better at what we now call marketing! Bryan, I'm afraid both rooflights are equidistant from the pillow end of the bed and very close. Even closing the skyl;ights doesn't help, as they do not seal completely (they are designed not to do so). I have had an initial reply from Seitz. Apparently there are two different versions of each skylight - with and without built-in ventilation, something that is not mentioned in their English language technical brochure at all. I need to find out which I have and get beck to them!

[Guest Brian Kirby]

Ah well. I did think my suggestion was a bit on the obvious side - still, you never quite know when the obvious will escape notice. Kind regards Brian

[Guest Derek Uzzell]

Mel: OK, I accept that my draught-excluder wheeze is a non-starter. I don't think it was my ineptitude at geometry that betrayed me (this time!), just woolly thinking and, if I'd bothered to look at the roof-lights in my 'van, it would have been apparent the idea was doomed. Proves what I've known for a long time - that my thought processes aren't what they were in my systems analyst days. As you observed originally, the blind design has an innate potential for rattling when drawn shut and, short of an overnight-only temporary fix (like Bill suggests) to wedge the guide-slots somehow, I can't envisage an effective solution. I believe that Mini and Midi Heki are similar to Remis equivalents in that the only difference between 'permanent ventilation' and 'non vented' versions is that the latter have additional seals: also that these seals are available from Seitz for retro-fitting. The CAK brochure advertises both versions of Mini (or Midi) Heki at the same price, which suggests the seals aren't particularly expensive. I don't see why adding seals to your roof-lights should improve matters rattle-wise when the 'lids' are open, but you never know your luck. Occasionally I've wondered what, if any, rules applied to high-level permanent ventilation in motorhomes. Is there a specific formula that relates ventilator area to vehicle size or is it just rule of thumb? I recall meeting a couple with a new 'van that had two big Heki 2 roof-lights that rattled while the vehicle was being driven and were uncomfortably draughty when it was parked. They had discovered that seals were available but the motorhome manufacturer wouldn't authorise them being fitted without an extra skylight being installed in the roof to provide the 'obligatory' permanent ventilation. As there were already other, smaller roof-lights present, the owners of the 'van were less than keen on this notion and ended up fitting the seals themselves.