Tuesday, 10 January 2012

What does he know about? A lot of hot air!

The day after we moved in was instruction day. It was also Christmas Eve. From one-thirty a series of plumbers, heating engineers and electricians came to show us how everything worked. The site foreman had scheduled them at thirty-minute intervals, although a lot of things were going on and some of them were waiting among the boxes.

The insulation and airtightness boss came along. I was hoping to hear something about the airtightness tests, and perhaps some apologies for the mistakes they had made, putting the machine the wrong way around, and forgetting to add insulation to the outgoing duct. 

As it was, he took me and the architect to the machine room, and proceeded to open the manual in front of him and try to find how it worked. In spite of his confident words, it has previously struck me that he doesn't know much chemistry, and his physics is a bit shaky. Now it seemed he didn't know how the ventilation system he had supplied worked.

The machine room, directly above the boiler, and housing a couple of power conditioners, is already the hottest room in the house. But it was about to get hotter. It's not a good place to jump up and down as the ceiling is low. The architect, who was sat behind me, patted me on the shoulder to try to prevent an outburst. I got up and told him to give me a shout when he was ready to explain how it worked. I did have a lot of important things to do, and I can read manuals myself.

I went back later and heard the explanation, and saw how to change the air flow. While there are still some volatile building materials, he suggested setting it to 180 cubic metres per hour, but usually, with four of us in the house, 120 cubic metres per hour should be enough. As the flow goes up, you can hear the water starting to gurgle as the air heading out of the house drops in temperature and sheds its humidity, because the capacity of air to hold moisture decreases with temperature.

A few days later, I finally got some time to sit down next to the machine with a manual, and I realised that it has no bypass on it. We had been talking about this for two years, and I had assumed it would be part of the system. I should have paid more attention to the model they installed. This may be bad news come summer.

Just as the heat exchanger works in the winter to maintain the inside temperature while taking fresh air from outside, it will also maintain the summer temperature. Matsumoto has a large difference between day and night temperature, averaging around 10 degrees. Almost every night, the temperature will drop below 25 degrees, but there's a possibility that the temperature inside the house is above 25 degrees. In this case, rather than exchange the heat from the house to warm up the incoming air, we want to expel the warmer air from inside the house, and take in the cooler outside air. 

Stiebel, and no doubt other manufacturers of ventilation systems, have already thought of this, and there is a bypass function, which will stop exchanging heat under those circumstances. Closer inspection reveals that this is not standard, but a slightly different model, with a plus on the end.