We have started to download the data from the temperature i-buttons at the Camden Passivhaus, and although it is too early to be able see the trends necessary to accurately report on how the house is operating, so far the results look really encouraging.

Please see the attached graph, the scale up the y-axis is temperature and the scale along the x-axis is time. The house is maintaining a very constant temperature and staying within a comfortable range. The second graph is from my old house over the same period last year, even with the heating on full in the evenings and morning I could not get the temperature over 20 degrees and it was even below 10 degrees at some points (low comfort and high bills)!

At the same time as monitoring the temperature we have taken the meter readings at the Camden Passivhaus, we took the meter readings on the 17th of Jan and on the 17th of Feb so we have a note of how much gas was used for this month. The gas used was 595kWh, the Passivhaus software assumes that every month 194kWh is required for your hot water, at this time of year the solar collectors will have covered about 44kWh of this. The total used for heating was therefore around 445kWh minus any inefficiency in the boiler.

Looking back to the Passivhaus (PHPP) software we used to design the house the projected amount of gas used for heating for this period was about 330 kWh at 20 degrees. The actual measured average temperature in the house from the data loggers was closer to 21 degrees; if we input this into the software it calculates that the gas usage for heating should have been 376kWh for this period of the year. So to summarise last month the house performed largely as expected, although it did consume about 69kWh more than calculated, some of this will be accounted for in the boiler efficiency and the rest in the assumptions we have had to make.

As we have not yet started all of the TSB monitoring we have had to make assumptions for how much energy was required for hot water and how much the solar panel contributed so these figures may not be very accurate. The software has a very conservative estimate for the hot water demand so it’s likely that more energy was used for hot water. We also are using standard London weather data which would need to be adjusted to the actual weather over this period. The last assumption is to do with the internal gains; these are set at 2.1W/m2 in the PHPP software but may vary from measured results.

Another reason for the slight increase will be that for the first year or so after a building has been constructed it is considered to be ‘drying out’, due to moisture drying out from the concrete slab and retaining walls and the internal plaster and other building materials. During this drying out period the house is expected to consume more energy than it’s designed to use.

We have asked the owners if they would like to try turning the thermostat down by 1 degree to see what affect this will have on the comfort and energy use. So next month we may have some more interesting results to report!

In light of all of this, it looks like the monitoring will provide some very interesting results. We will be starting a more involved monitoring programme in the next few weeks, so watch this space……

Temperature readings from the Camden Passivhaus, 17th - 31st January 2011

Temperature readings from top floor flat of traditional London townhouse, 21st January - 4th February 2010