Monitoring energy data
Energy Data Monitoring: results from a Passivhaus using no heat energy whatsoever, compared with results from a London Terraced House using occasional heating
Passivhaus and the Muse
The Muse, my home and also my office, was started on site in 2002 before I knew about Passivhaus techniques emerging in Germany; but together with Max Fordham we discovered an approach, unique in the UK at that time, that is almost identical to the Passivhaus approach. Wolfgang Feist, the founder of the Passivhaus Institute, has visited the Muse and announced at the AECB conference this year that he is keen to provide certification subject to satisfactory energy monitoring and careful checking of our PHPP analysis. So until our various other Passivhaus projects are complete, energy and temperature monitoring of my own house provides the best possible comparison of energy use with traditional housing in the UK.
Energy monitoring at the Muse
At present, temperature recording is done using a number of i-button sensors which are rigorously programmed by Sarah Sandison in my office to take temperature readings every 10 minutes, 24 hours a day for 12 days. After 12 days the sensors are swapped for new ones and the data is downloaded into Excel graphs. Temperature data is collected from several different locations inside the house and simultaneously an external air temperature sensor takes the air temperature outside in the shade and another sensor measures insolation, to indicate hours of sunlight. Shortly flow metres will be located on the solar water heating circuit and the gas water heating circuit in order to determine how much of the hot water is provided by the solar panels. Also heat flow sensors will be located on the underfloor heating circuits as proof that space heating has been found to be unnecessary in this house apart from in an extreme weather event and to record the amount of heat energy used in that event.
Meter readings are also rigorously recorded every Monday morning.
CO2 monitoring has also commenced and will compare fresh air levels in a Passivhaus and a traditional house. In the Summer the Passivhaus is ventilated by opening the windows but in winter, to save energy, ventilation is normally achieved by a heat recovery ventilation system. Monitoring in Germany shows that this results in excellent quality winter air, without wasting heat through winter ventilation losses. We will also compare winter air quality with and without using heat recovery ventilation. We will also compare winter air temperatures when using heat recovery ventilation and when using opening windows to maintain an acceptable and constant level of air quality. The acceptable level, according to EU advice, is at all times below 1500parts per million of CO2. Conventional UK schools, places of work and bedrooms often have CO2 levels exceeding 3000 parts per million, which is more than 10 times what our ancestors have breathed for tens of thousands of years, so we believe such levels are unhealthy. We prefer to keep internal CO2 levels below 1000ppm wherever possible, and below 1500ppm even if the house is full of people. In a domestic house this can be done at the cost of about 30 watts of energy going into the latest German heat recovery ventilation units during the winter months. (My own Dutch unit uses about 45 watts in normal domestic mode but is a few years old and was not Passivhaus certified).
Energy monitoring at a local terraced house
Simultaneously to energy monitoring the Muse, Sarah has been monitoring her own flat in a terraced house nearby that has occasional heating, supplemented by heat rising from a flat on the ground and lower ground floor. Daniel Hayes has also started monitoring his own flat nearby, a recent developer conversion of a former warehouse building. His intention also is to use the minimal amount of heating and to record the amount of time heating is used.
Results so far
We have initially provided one example for the period 19th October 2009 to 2nd November 2009. During this period house has, apart from momentary temperature drops beside an open front door, maintained internal temperatures between approx 20 degrees and 26 degrees celcius without any need for supplementary heating. By comparison, the traditional house has been consistently 5 – 10 degrees celcius lower than the Passivhaus in spite of receiving some supplementary heating.
Occupancy levels and rates of air exchange also have a bearing on the results and a careful analysis of these factors is underway.
In due course we plan to publish the results in detail. We also plan to upgrade the monitoring to allow live readings to be published on our website. The techniques used will exactly match the standards set by the Technology Strategy Board and the Energy Savings Trust for our Government funded Retrofit for the Future research projects underway for four social housing projects. The same techniques will be adopted on all our Passivhaus projects.