Monday 14 November 2011

Not too late for the punctual thermal bridge - The North side revisited

One good thing about having a 12 month delay in a building project is that it gives you plenty of opportunities to reconsider previous decisions. You spend hours, days and weeks thinking about things, then come back to them months later with a fresh opinion. Then you try to remember why and how you came to the decision in the first place. 

There are always many ways of doing things, and often there is something radical that you've never seen in a house before. There is usually a good reason why it has never been seen, either that there is a flaw in the idea, or the conservative nature of builders and architects. Materials and science have moved a great deal in the past few decades, but building sensibility still goes back hundreds of years. A lot of dimensions can be calculated, rather than guessed by eye or by rules of thumb, and this could reveal extra possibilities, or if the architect doing the calculations is semi-numerate, it could further restrict the possibilities.

Let me digress into a couple of examples from aeronautics. In the 1940s when Howard Hughes made his eight-engined Spruce Goose, the largest flying boat ever, about the same length as a 747, but with twice the wing area, the science of aerodynamics was young and aircraft design was more of a craft. The wings, scaled up from smaller working designs, were so big you could walk down the inside. A little bit earlier, in the 1920s when airships seemed the only logical alternative to crossing the atlantic by sea, and R100 airship was being designed, they needed to calculate the stresses on each beam and wire of the massive frame that kept the balloon full of hydrogen. They used a computer for this, which at the time was a person with a slide rule and a pad of paper. If they found that any of the wires had negative tension, they would send it all back the designer. 

Back to our little world, at the end of the day, you just have to make a decision, and then stick with that decision, and convince yourself it is the correct one. Then move on, as there are plenty more decisions to make. 

Of course, when the house is built and you start living in it, and those decisions become solid objects, you find out whether you did the right thing or not, and if you want to find out whether it was the right decision, then keep reading. When we do move in, though, after the investment of time and money, there's a high chance that I'm going to consider the house to be close to perfect, and I'll look around, through or away from any problems that there are, and do my best to enjoy the good bits. Human beings are, after all, very flexible animals when it comes to living environments.

It has been very tempting, whenever part of the building comes up that we have not been entirely sure about, to take the full opportunity offered by the questions "are you sure?" or "do you really want to do this?" or "what, exactly, are we supposed to do here?" that the builder asks the architect, luckily in our presence.

I suspect that, had we not started to get heavily involved with the builder, insisting that we are involved in any meetings with architect, and if I hadn't been visiting the building site, with a camera, pretty much every day, things would have been very different. For a start, we probably would have moved in a few months ago. All the questions that we see being asked, as the builders scratch their heads over the architect's drawings, would have been worked out in some haphazard fashion, filled with builders guessing what the architect meant and hoping for the best, and the architect demanding constructions based on his own prejudices, either forbidding materials that he doesn't like, or using them indiscriminately because we had the nerve to ask him to use them. A lot of the time, I suspect the architect would have just presented it as a concept in pencil on paper, and left it to them to work out how to make it. Almost none of the time would he have been thinking about what we really want.

So, anyway, when it came to the roof over the front door, we were able to change the plan. 

The plan had been to have a sloping, transparent roof over the two doors on the north side of the house. The front door is to the west of the north wall, then there are seven steps up to the entrance to the este room. With the doors being at different heights and there being windows and glass doors, it seemed like a good idea to have a transparent roof, at an angle.

It seemed to me a very bad idea to puncture the thermal envelope, but according to the architect, this was just too difficult to do without puncturing the wall with beams, although in a couple of days the carpenter seems to have managed to remove the protruding beams, and construct a new roof. Evidently moving hammers, saws and three-metre lengths of wood is more difficult than moving pencils, erasers and the computer mouse.

It had always seemed to me a good idea to have a transparent roof, as this will let in more light, but when it came to it, the architect had no idea how this was going to be done, and the ideas he had all sounded like they would look terrible. One big issue with the roof is that it is likely, at some point, to be subjected to falling bits of ice from the roof above. These could actually be quite large and serious as the roof is highly insulated, so the heat escaping from the house is not going to have a very good melting effect. Also there is a bit of wall sticking up from the north roof to the higher south roof, so the top part of the roof will be in permanent shade for half the year. And the north roof has quite a shallow slope, so snow is likely to stay there for a while, going through a melting-freezing cycle and getting harder and harder. Anything transparent is not going to be as strong as a solid roof, and liable to be damaged by such falling ice. Then there are fire regulations, which need a whole new post to cover both their simplicity and the extent to which they are interpreted and ignored.