PART 2: PART PRÀCTICA
E. Procés d’anàlisis de dades
The weather file used in IES<VE> has the “file name”.fwt which can be exported to Excel allowing manually input of recording climatic data, then can be imported back to run the simulation using the customised weather conditions. The selected periods of time for empirical calibration were when the building was unoccupied for more than one week. It is necessary to mention that the building is still in progress at the finishing stage that is slowed down by the owner. The unit is interfered at reasonably high frequency of three days stay a week, excluding annual vacation.
Because the construction is lightweight thus it could be back at the “normal” state after a reasonable amount of time, says 1- 2 days during summertime. Because the influence on room thermal conditions from the act of occupant’s opening/closing windows does not last too long. Figure 4-11 to 4-12 show the variation in hourly temperature data between the measured air ambient temperatures, room air temperatures and the simulated results. The study was conducted where the modellers had no knowledge of the measured building performance. The measured indoor air temperatures followed the changing pattern of outdoor temperatures, with the slightly delay of about two hours in
peak temperature. The simulated air and operative temperatures showed good agreement with measurements during the unoccupied period, the maximum difference is 0.7°C.
Additional validation work as shown in Figure 4-13 and 4-14 was required as there was some changes on the building envelope. The window blinds were added in the test building after summer 2010 to enhance privacy for the owner. The blinds also reduced heat gain from solar radiation and higher outdoor air temperatures that the differences between the peaks in indoor and outdoor air temperatures during the selected days were smaller, as shown in Figure 4-13, in comparing with those in Figure 4-11. Besides, the test building owner was doing the finishing work that affected the building envelope itself. For example, during August 2010, the cement board was built within the long sided external wall or the hole of 100mm diameter on bathroom floor was made for water excavation in October or mechanical ventilation heat recovery system was being built over November and December 2010. It was necessary to note that the first stage validation used the airtightness test result conducted by the researcher, the building test owner under support and supervision of Dr Colin Oram from the University of Warwick. An official airtightness test conducted by 3rd party (BSRIA Ltd) was undertaken after some interference within the building envelope as mentioned above.
These modifications were taken into account in the simulation work.
The following reasons are to be determined as resulting in errors:
- Inaccuracy of the simulation tool itself (not to be discussed in the project).
- Error from assumption and approach: It is very important to bear in mind that the simulation is an attempt to reflect the reality. For example, thermal transmittance for each building element was calculated by the assumption of one dimensional heat flow, constructional layers were planar and heat path forms as the perpendicular to the surface and internal/external surface temperature was uniform within the surface.
- Inaccuracy of measuring instruments: The equipments in use to measure indoor air temperature possessed a significant inaccuracy range of ±0.1°C.
- Error from location: The climatic data inputted into the simulation were collected from a place of 1.1 miles distance to the test site which has slightly difference in external conditions. For example, it was observed that the temperature difference varying within (-0.57°C to 1.32°C) between air temperature from the weather station and outside the test building over a period from 7th to 12th October 2010. And the instruments
measuring air temperature located opposing the wall instead of at the room centre because the readings had been affected by solar radiation.
Figure 4-15 illustrates the coldest period last winter (December 2010) when the outdoor dry-bulb temperature was within the range of (-12ºC to 5ºC). It was observed that the difference in hourly air temperatures between measurement and simulation that the simulation results follows the air ambient temperature whilst the reading deters with at nearly 8ºC difference at 00:00 on 15th December. It was because the occupant utilised a small fan heater in order to generate a warm space for working indoors hence the thermal conditions were affected. It accounted for the cool down of the building unit when the owner left the building at 20:00 on 14th December 2010. The indoor air temperature decreases slowly with the combined effect of remaining heat indoor and fluctuated outdoor air temperature as can be seen from day 1 to day 3. The validated model simulation ran through this period and illustrates that it takes around 5.5 days that the building lost totally the heat generated during the occupancy period. That might be a potential key performance of the ErgoHome in saving energy because the ability of maintaining the warmth can improve the use of heating device in term of intermittent operation. Also, on the right hand side of the graph, there was a sudden rise in temperature readings when the building started to be occupied at 10 am on 21st December 2010.
Figure 4-16 is the graph showing readings of outdoor and indoor air temperatures and the heating energy was used for the test building. However, there was not a comparison of whole house energy consumption between simulation results and measurement. It was due to the amount of work loads for simulation and field data work to validate the simulation model of heating system which could go beyond the timeframe of research work. Several studies: Lomas et al. (1997), Judkoff and Neymark (1995), Broomfield 1999) and Strachan (2005) showed significant amount of work and reasonably high uncertainties in errors between simulation and measurements. For instance, the case study: Lisses House collaborated between BRE and EDF reported that the comparison of whole-house energy consumption over the complete experimental period (more than two winter months) revealed errors ranging from -4% to +26% (Broomfield, 1999).
Figure 4-11: Comparison of hourly air temperature over a selected hot period in summer 2010 0
5 10 15 20 25 30
Fri, 11/Jun Sat, 12/Jun Sun, 13/Jun Mon, 14/Jun Tue, 15/Jun Wed, 16/Jun Thu, 17/Jun
Deg C
From 11th June to17thJune 2010
Outdoor air temperatures Air temperatures at the living space Simulation results
Figure 4-12: Comparison of hourly operative temperature at the living space during the selected hot week in summer 2010 0
5 10 15 20 25 30
Fri, 11/Jun Sat, 12/Jun Sun, 13/Jun Mon, 14/Jun Tue, 15/Jun Wed, 16/Jun Thu, 17/Jun
Deg C
From 11th June to17th June 2010
Outdoor air temperatures Operative temperatures at the living space Simulation results
Figure 4-13: Comparison of hourly air temperature at the living space in a selected period in summer 2011 0
5 10 15 20 25 30
Tue, 26/Jul Wed, 27/Jul Thu, 28/Jul Fri, 29/Jul Sat, 30/Jul Sun, 31/Jul Mon, 01/Aug Tue, 02/Aug Wed, 03/Aug
Deg C
Hot period from 26thJuly to 03rdAugust 2011
Outdoor air temperatures Air temperatures at the living space Simulation results
Start of occupancy
Figure 4-14: Comparison of operative temperature in the living space with installed internal blinds to prevent solar heat gain
0 5 10 15 20 25 30
Tue, 26/Jul Wed, 27/Jul Thu, 28/Jul Fri, 29/Jul Sat, 30/Jul Sun, 31/Jul Mon, 01/Aug Tue, 02/Aug Wed, 03/Aug
Deg C
Hot period from 26th July to 03rdAugust 2011
Outdoor air temperatures Operative temperatures at the living space Simulation results
Start of occupancy
Figure 4-15: Comparison of hourly air temperature at the living space in winter 2011 -15
-10 -5 0 5 10 15 20 25
Wed, 15/Dec Thu, 16/Dec Fri, 17/Dec Sat, 18/Dec Sun, 19/Dec Mon, 20/Dec Tue, 21/Dec
Deg C
From 15thto mid day 21st December 2011
Outdoor air temperature Air temperature at the living space Simulation results
Start of occupancy
Figure 4-16: Monitored air temperatures when the test unit is heated by immersion heater, winter 2012.
0 1 2 3 4 5
-5 0 5 10 15 20
27/01/2012 28/01/2012 29/01/2012 30/01/2012 31/01/2012 01/02/2012 02/02/2012
Energy load (kWh)
Deg C
LS air temperature Bedroom air temperature External air temperature Heating load
4.6 SUMMARY
The field data from monitoring process shows that the indoor temperature changes steadily, around one fifth compared to the fluctuation of air ambient. The capability of maintaining a consistent indoor air temperature/operative temperature of the SIPs unit can be understood as improved thermal comfort. This is achieved by high level of insulation and airtightness of the building envelope. During the warm period, a small amount of heat might be required to achieve desired comfort level because the unit loses heat very slowly during the night, it picks up heat quickly by solar gain through its glazing fenestration and trapped this useful heat to maintain the warmth indoors.
However, in summer 2010 overheating occurs inside the EH unit with the bedroom experienced the highest level amongst the rest due to the room volume and its high glazing areal facade facing the west. This issue was then solved by installation of internal shading devices of solar screen blind offered by Intelliglaze Ltd for summer 2011. It appears that the overheating risk is eliminated despite of the increase in the warmth this summer compared to last one (peak outdoor air temperature was up to 25ºC in end of July and last week in September 2011). Because it is shown in the field monitoring data that during the peak of external temperature the peak in internal temperature was delayed and equal or less than the outdoor level. However, during the daytime, the room remains gloomy that light bulbs are required if allowing working task taking place. With regards to ventilation performance that natural ventilation strategy is sought to apply in passive design strategy, it is shown that by opening the windows, the room temperature is cooled down to meet outdoor air temperature level very quickly, revealed by 10 minutes readings. Opening the French patio door will allow an effective and urge cool down if peak temperature indoors is undesired. During heating period, it was recorded of such severe condition in winter 2011, when outdoor air temperatures falls down to -12ºC, the indoor temperature varied amongst -5ºC. The two previous days of this coldest day, the outdoor temperature varies between -5 to 0 ºC and the indoor temperature varies between 0 and 5 ºC. The owner while occupying the EH unit used a fan heater to provide warmth during his working and it was recorded that it took 3 days air temperatures logging at the living space are closer to the simulation results. This can be interpreted as resulting in saving heating energy through shorter operation period and higher intermittent for the heater device, and in improved thermal comfort within the space.
Validation of simulation model includes analytical verification at the first stage to evaluate the accuracy of building model by empirical values or known calculated solutions. The simulation is then validated by empirical comparison that comparing hourly data or shorter interval between simulation results and monitoring of the unoccupied experimented building with the real weather data collected at the nearest to the construction site. The validated model simulation allows further development for integrated design solutions where passive design strategies are sought through and verified to be effective or not.