Sunday, 15 April 2012

The blind man came to see the house

With our triple-glazed argon-filled low-e windows we don't really need curtains. At least that's what the people selling the windows said. Actually when it's really cold outside, some blinds would help reducing heat loss through radiation, especially with the lack of emmissivity in the room. Also blinds give us a bit more privacy, and may help keep some of the summer solar radiation out, although I think geometry and the balcony will be more effective. Just because we don't really need them, doesn't mean we don't want them.

Anyway, for aesthetic purposes as well as mitigating the flow of heat, we want broad wooden venetian blinds along the ground floor on the south. From a privacy perspective, it's easy to angle such blinds so that it's possible to see out, down to our terrace and garden, without being seen into from the higher windows of the neighbouring buildings.

We also need a blind in the washitsu, the tatami room, for privacy when guests are staying in there. Personally I'm quite happy for anyone who gets to the front door to be able to peer into that room, but this is not a unanimous view among members of the household. I was originally hoping that we'd get a shoji paper door across that window, but at some point it was decided that this would not match the Germanness of the window. Perhaps sliding shoji doesn't go with swinging windows. Perhaps for this reason, perhaps for other reasons best known to the architect, there is very little clearance between the top of the window and the ceiling in this room. Around 40 mm from the ceiling to the top-sill, then 35 mm from the top-sill to the top of that window sash when it opens, inwards. That's only 75 mm, which is not a lot to fit a blind in when it rolls up to the top, as it inevitably will. And I have some memory of the ceiling having been raised, so there would have been much less space to put the blind in.

Perhaps this was in the architect's blind spot. Or perhaps he just turned a blind eye. 

The blind we were looking at for this room was kind of a double roll blind, that has alternating strips of transparent and opaque material doubling back on itself, so, as you let the blind down, it goes from being opaque to having strips you can see through. When I say opaque, it's not completely opaque like air-raid curtains, or the wall next to the window; more strictly speaking it's translucent. The critical part for our concerns is that the width of the roll, when rolled up, is 78 mm, a whole 3 mm wider than the gap between the wall and the open window. Not ideal. Because the blind is doubling back, it is actually twice as long as the height of the window, so a single roll-blind would probably be significantly thinner, and should fit in the space. It wouldn't give us this find level of transparency adjustment though. Another kind of these blinds has two different rolls, with different colours, and presumably each roll would be thinner, but that blind seems only to be attachable in a vertical orientation, with one roll on top of the other. You could say it's a case of the blind leading the blind. 

Onto the South side, the middle big window has a bit of ceiling sticking out on the left side, and a beam coming across on the right side, so we are limited for clearance there too. There is about 150 mm from the protruding ceiling to the window top-sill, then about 40 to the top of the window sash when it opens. The stark choice is either a narrow blind, where there is a few centimetres' gap on each side, or a shorter blind, but the shorter blind would need to be half a metre shorter to make a significant difference to the thickness of the slats when closed. 

One suggestion to get around this was to make the blinds wider than the box with the mechanism in it. It looks like the total height of mechanism plus slats was over 200 mm, but taking away the box width from this, the width of the slats seems to be less than the 150+40 gap we have between the protruding ceiling and the top of the beam. The blind man said he was going to find out from the manufacturers whether they could produce blinds like this, where the slats are wider than the box. He got back later saying that they could make blinds like that, but the whole thing actually needed about 300 mm, so there wouldn't be enough room for the slats. I don't completely believe this, as usual, and would like to see some numbers and actual clearances before a decision is made. I can appreciate their desire to leave wide clearances, and plenty of margin for error, but I also have a strong desire to have blinds that will cover the whole of the window reveal. 

And just in case you thought you'd seen the last of the blind puns, I'm going to blindside you with another one.