From the beginning of February, when it started getting to around minus ten each night, we were putting down the shutters on the upstairs windows each night. They may have some insulation effect, but their cutting down on heat radiating from the house is probably more significant.
Joe, who is eight, correctly surmised that the best time in the morning to put the shutters up is when the light comes on to show that the solar panels are producing electricity, and the shutters should come down in the evening when the light goes out. According to the passive house software, the heat coming in through the south-facing windows is 790 kWh in February, which is over 20 kWh per day. This goes up to 927 kWh in January, over 30 kWh per day. It's 843 in December and 743 in March. Overall, the south facing windows bring in over three times more heat than they lose, so even if it's very cold outside, any solar radiation coming in is going to make up for the thermal losses, and certainly be more of a benefit than any increased insulation from the shutters.
Anyway, I got back one evening to find that one of the shutters had come down a few centimetres. I assumed this had been partially put down, so I switched it to come down properly. It didn't, but there were whirring noises. I switched it to go up. More whirring noises.
Now this shutter happens to be outside the window opening onto the balcony. Lucky, I thought, as I can just open the window and try to help it up or down. Actually I got Joe to help with the controls, while I stepped out onto the balcony to try pushing the shutter up while he was switching the shutter to close. I thought perhaps it was a little disengaged.
As it turns out, it was more than a little disengaged, and after some more whirring and a little clunking, the whole of the shutter came crashing down to the bottom, leaving me standing on the balcony in bare feet on a very cold afternoon. It was impossible to get the shutter up again, as it was not coiling properly inside its case. The shutter case uses some kind of six-pointed star screwdriver, so I couldn't open that to get the shutter up. I was stuck.
I considered climbing down from the balcony, but decided it was best to appeal to my better half's better nature and get her to bring a ladder out. The sharp tongue of a wife who is both angry and right, while certain to cause some injury, would be much less painful than potential injuries from sliding and landing on the hard tiles below.
Before fixing this, the suppliers, who also provided our windows, needed to get parts for the disengaged shutters, and there was a chance that they would not be able to fix it until we got back from our travels. They assumed that we would be leaving the shutters down while we were away, but I was looking at the thermal gain from these windows. Of a total almost 16 square metres of glazing on the south side of the house, the shutter in question was covering a double window, with 1.5 square metres of glazing. That's 10%, so a couple of kWh a day. The equivalent of a heater on for an hour. It can still be quite chilly at the end of March, so we didn't want to be turning heat away while we were away.
As it happened, the parts arrived and it was fixed in time. What had happened, apparently, was that the for the motor to stop when the shutter was going up had been set above the actual level of the shutter when fully wound up. The switch goes three ways: up, off and down. If the shutter is down, when the switch is switched to up, it will go up until you switch it to off again, or if you leave it it will go all the way to the top, then it should switch off inside, even if the switch is still set to up. So the first few times we used it, we had obviously been very careful and attentive, marvelling at the wonder of this technology, and staying to switch it off as soon it reached the top. After a week or so, we switched it to go up and left the switch, confident that it would automatically stop. However, it wasn't switching off and the motor was still working away on the shutters, presently rending them from the axle.
All is now well, and I'm beginning to wonder what temperature it is actually worth putting the shutters down at night, as the effects on radiation must be minimal.
