Monday, 9 April 2012

Temperature Data

Here's another data graph for you, covering the period from the winter solstice to the end of March.

The green bars correspond to the amount of energy being generated by the PV and thus the amount of sunshine. The purple bars show the external temperature and the brown the hours the heating has been boosted inside when the temperature has dropped. These are plotted against the lines for the house temperature on the top (red), first (yellow) and ground (blue) floors.

I should point out now that this is a domestic record of what's happening in the house: the energy records are accurate but they aren't always taken at the same point each day and the temperature readings come from a normal thermometer rather than a more scientific instrument. Nonetheless this records what's been happening in this particular Passivhaus over the past three months.

The house has been good at maintaining its base temperature but although that has been 20 degrees on the top floor it was too cool to sit in the rooms on the ground floor for several months without adding an extra heater. The ground floor temperature is closely linked to the external temperature, but it takes about 24 hours for changes outside to be felt on this floor. It was only once we had the high temperatures and sunshine at the end of March that the temperatures on all three floors reached much the same level. The house's heating doesn't have much impact on the ground floor and only slightly more on the first floor, but it has a direct (and immediate) effect on the temperature of the top floor, presumably because the warm air rises to the top of the building and, despite the coanda effect, doesn't hang around to heat the rooms on the lower floors. Is it supposed to work like that? Perhaps one of you Passivhaus engineers can let me know...

The graphs suggest the first floor is the most responsive to sunshine and it certainly receives more than the floor below where the wall and house of a neighbouring property shadow the windows for more of the day. On the other hand, it's also the floor containing the kitchen so the extra warmth from cooking may be what's keeping it warmer than the ground floor.

The top floor is the most responsive to the internal temperature of the house and less affected by sunshine. The temperature on this floor climbed at the end of March as the lower floors became warmer and the warm air rose but we got into the habit of opening the rooflights to cool the rooms and kept the blinds closed to exclude direct sunlight during the day. The question, of course, is will this be enough to keep the house comfortable in the event of a heatwave in the summer?

PS: Do note how little we've actually had to have heating on this past three months - a bit different to a 'normal' house

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