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Table of Contents
Energy use – measurement results
The heat requirement of a building is mathematically determined – the actual consumption depends on many other influences, e.g. user behaviour and the weather. Years of experience have provided statistically reliable measurements of actual consumption values. The reliability of the Passive House concept can be judged from these results.
With all building standards there are significant differences in consumption due to user behaviour, even in the case of identically constructed buildings. The consumption must therefore always be measured for a sufficiently large number of identically constructed homes so that utilisation-dependent influences can be averaged out, thereby enabling a comparison of the building quality. Fig. 1 provides an overview of measurement results from 41 low energy houses and a total of 106 Passive House homes in Germany. A number of insights can be gained from these measurement results.
Low-energy housing development
For comparison, the low energy settlement in Niedernhausen with 41 terraced houses is used as a reference. The individual values of the heat meter readings for the year 1994 are shown in Fig. 2 (measurement: [Loga 1997] ). The average value for all homes measured is 65.6 kWh/(m²a). Here and subsequently, the living area is used as the reference value for the consumption, as usually done for heating cost invoices.
This average value is considerably lower than the average heat consumption in existing housing stock in Germany. If a space heating value of 112 kWh/(m²a) is used as the current (2013) reference value for Germany, corresponding to the average heating consumption in apartment buildings that are invoiced according to consumption [techem 2014] , then the consumption in 1997 in the low-energy settlement is at least 41.5 % less than today's average consumption. Incidentally, although built in 1991, the construction standard of this settlement is still better than the requirements of the currently applicable German energy standard (EnEV).
Fig. 2 also shows that the individual values are scattered around the average value depending on utilisation. The influence of user behaviour on the consumption is even quite high. However, this is the case not only in energy saving houses but also in poorly insulated buildings. The standard deviation (a measure of the mean deviation of the individual values from the average value) for this settlement is 13.6 kWh/(m²a) or 21% of the average consumption value.
The deviations due to user behaviour average out to a great extent if an average value is used, even more so for a large number of identically constructed units. The average consumption value for this housing development is statistically accurate to ±2 kWh/(m²a). It is therefore statistically secured that the low-energy standard leads to significant energy savings (41.5% ± 1.8%) compared with the current building stock.
Passive House settlement in Wiesbaden/Dotzheim
This was the first Passive House settlement project in Germany (built in 1997, by Rasch & Partner) and consists of 22 houses. Fig. 3 documents the heat meter readings of the 1998/99 winter season. The average value was determined as 13.4 kWh/(m²a). This means that the average consumption of the Passive House settlement is 80% lower than that of the low energy settlement in Niedernhausen.
The standard deviation of the individual values of the Wiesbaden settlement is ±5.3 kWh/(m²a) and is much lower than that of the low energy settlement. However, relative to the much smaller average consumption, the effect of user behaviour is more noticeable. The determined average value is statistically accurate to ±1.1 kWh/(m²a). The energy savings due to the Passive House Standard are therefore statistically reliable. These are:
(80% ± 2%) in savings compared to the low energy standard, and at least
(88% ± 1%) in savings compared to the average heating consumption in Germany
Passive House settlement in Hanover/Kronsberg
The Passive House settlement in Hanover/Kronsberg consists of 32 essentially identical terraced houses built as mixed constructions according to the Passive House Standard. The settlement was built in 1998/99; all units were designed individually. These were part of the Europe-wide CEPHEUS project. Fig. 4 documents the heat meter readings in the heating season of 2001/2002. The average value is 12.8 kWh/(m²a). The consumption in this Passive House development is therefore about 81% less than that of the low-energy development in Niedernhausen ([Peper/Feist 2002] ).
The average consumption values of all occupied Passive Houses in the housing development as measured by means of heat meters in all studied periods were as follows:
1. Heating period 1999/2000: 14.9 kWh/(m²a)
2. Heating period 2000/2001: 13.3 kWh/(m²a)
3. Heating period 2001/2002: 12.8 kWh/(m²a)
The extremely low heat consumption values for the Passive House housing development in Hanover/Kronsberg are therefore also statistically secured - the standard deviation of the individual values is 6.6 kWh/(m²a), the average value is accurately determined to ±1.2 kWh/(m²a).
Passive House settlement in Stuttgart/Feuerbach
The Passive House development in Stuttgart/Feuerbach with a total of 52 terraced and detached houses was finished in the year 2000 by the architectural practice Rudolf. Fig. 5 documents the consumption values of the 2001/2002 heating season. The average consumption value is 12.8 kWh/(m²a) [Reiß/Erhorn 2003] . In this housing development there are a few outliers that are clearly identifiable as such.
The extremely low heat consumption values for the Passive House housing development in Stuttgart/Feuerbach are also statistically secured – the standard deviation of the individual values is 5.5 kWh/(m²a), the average value is accurately determined to ±0,8 kWh/(m²a).
Conclusion
Independent confirmation from other projects
Further empirical studies in other areas of the world have independently confirmed the results documented here:
- A study by Treberspurg et al., which can be found in the Conference Proceedings of the 14th International Passive House Conference, analyses the measured energy consumption of six Passive House apartment complexes in Vienna; the average space heating consumption here was less than 10 kWh/(m²a).
- Measurement results from the largest Passive House settlement in Innsbruck, Tyrol with 354 housing units (completed in 2009) also demonstrated that expectations were met (Passive House Lodenareal)
- Measurements by Johnston et al. for 25 low-energy projects in the UK [Johnston 2014], see also UK-results on energy performance
- Monitoring for residential buildings in the world's largest Passive House settlement in Heidelberg (Germany) known as Bahnstadt. The buildings in this settlement were studied using a simplified procedure for measuring heating consumption values (minimal monitoring). The average annual consumption of 1260 homes with a total living area of over 75 000 m² in the year 2014 was 14.9 kWh/(m²a). The amount saved in comparison with the reference settlement was 77%. This statistically high number of residential buildings built by different property developers and architects convincingly demonstrated that successful implementation on a broad scale is possible [Peper 2015]. (Note: these measurements were carried out in the first year of operation, in which disruptions in the operation process often occur (e.g. change of tenants, adjustment), as experience has shown. Even so, the Passive House buildings were already functioning faultlessly).
Inferences
The measurements in the realised Passive House settlements show that:
- The individual measures, i.e. thermal insulation, triple low-e glazing and heat recovery were effective. Deviations of more than about 1 kWh/(m²a) would have been identifiable in the average values, but did not occur.
- The calculation method according to the PHPP and the applied boundary conditions proved successful in practice. The differences between the calculated balance and the measured values are minimal.
- According to the present consumption statistics, additional heat losses such as heat transmission losses or high window ventilation losses cannot have a decisive effect; they must be within the limits determined with ±1 kWh/(m²a) and are therefore insignificant.
Summary
Different users, even if they live in identically constructed houses, frequently have very different consumptions: deviations of ±50% from the average value are not exceptional. This applies for all energy standards. The main reason for this lies in the different set temperatures during the heating season. The maximum usage-dependent consumption values in Passive Houses are also still significantly less than the lowest consumption in conventional new buildings.
The Passive House concept demonstrably and repeatedly leads to very high energy savings which amount to more than 90% compared to existing building stock and 80% on average compared to the requirements for new constructions. These saving amounts have been confirmed through statistically significant empirical studies and in a large number of projects [Treberspurg 2010].
Notes about the units applied
1 kWh (kilowatt hour) is a unit of energy. One litre of fuel oil or 1 m³ natural gas purchased have a heating value of almost 10 kWh.
The specific heating value qH has been used all throughout for the comparison: qH = QH / AEBF.
QH is the measured (useable) heating consumption. The heating distribution was measured at the heat transmission point for all measurement projects (usually by means of heat meters; more details about this can be found in the scientific reports referred to in the text). This measurement records distribution losses and potential heat transmission losses. However, the measurement does not included any heat generator losses.
Example: heat meters with an m-bus output were used in all 32 terraced houses in the Passive House development in Hannover-Kronsberg. The entire measuring technique is described in [Peper/Feist 2001] . In addition, there is an overall heat meter in the central supply for each row of houses for checking the results.
This measurement includes distribution and heat transmission losses. However, it does not include the heat generator losses.
AEBF is the treated floor area. For all results given here, this is the heated living area; thus the area reference on which heating bills and all published statistics are based was selected. It is important to note that the area AN in accordance with the calculation procedure in the German standard EnEV is approximately 20 to 30% larger than the actual living area. Energy parameters based on AN appear to be much lower than they actually are. For this reason, only the actual net floor area reference is consistently used for our calculations.
Note for mathematics experts
We have inserted the appropriate Gaussian or normal distribution (Wikipedia Website) into the diagrams:
1/(σ√2√π)∫ e - ½ (x-μ)²/σ²,
to be precise, their inverse, i.e. the “Norminv” function which is available in spreadsheet programs. For this,
- μ describes the average value
- and σ the standard deviation.
Additionally, the number of the respective buildings in each sample group has been given as n. A look at the graphs shows that the heating consumption values of identically constructed objects are very well approximated by a normal distribution. More details can be found in the CEPHEUS Final Report [Schnieders/Feist 2001] (Chi-Quadrat-Test; Kolmogoroff-Smirnov-Test). In this paper it is also discussed in more detail, what effect it has if the distribution is cut off at zero. Obviously, in the case of Passive Houses, this does not make much a difference. But, for a zero-Energy-House only the positive deviations will remain; adding non-zero to zero just by statistical effects.
Literature
[Ebel 2003] Ebel, W.; Großklos, M.; Knissel, J.; Loga, T. und Müller, K.: Wohnen in Passiv- und Niedrigenergiehäusern – Eine vergleichende Analyse der Nutzungsfaktoren am Beispiel der „Gartenhofsiedlung Lummerlund“ in Wiesbaden-Dotzheim, Endbericht / Energie; Institut Wohnen und Umwelt; Darmstadt 2003.
[Feist/Loga/Großklos 2000] Feist, W.; Loga, T. und Großklos, M.: Durch Messungen bestätigt – Jahresheizenergieverbrauch bei 22 Passivhäusern in Wiesbaden unter 15 kWh/m² Wohnfläche, in BundesBauBlatt, 3/2000, S. 23-27.
[Johnston 2014] D. Johnston, D. Farmer, M. Brooke-Peat & D. Miles-Shenton (2014): “Bridging the domestic building fabric performance gap”, Building Research & Information, DOI: 10.1080/09613218.2014.979093; link: http://dx.doi.org/10.1080/09613218.2014.979093
[Loga 1997] Loga, Tobias; Müller, Kornelia; Menje, Horst: Die Niedrigenergiesiedlung Distelweg in Niedernhausen, Ergebnisse des Messprogramms, 1. Auflage, Institut Wohnen und Umwelt, 1997.
[Peper/Feist 2001] Peper, Sören; Feist, Wolfgang: Messtechnische Untersuchung und Auswertung - Klimaneutrale Passivhaussiedlung Hannover-Kronsberg; 1. Auflage, Proklima, Hannover 2001; You may downlod an English version on the Passive House Institute website.
[Peper/Feist 2002] Peper, Sören; Feist, Wolfgang: Klimaneutrale Passivhaussiedlung Hannover-Kronsberg Analyse im dritten Betriebsjahr; 1. Auflage, Proklima, Hannover 2002; You may downlod an English version on the Passive House Institute website.
[Peper 2015] Peper, Sören: Bahnstadt Heidelberg, Minimalmonitoring für ausgewählte Gebäudekomplexe. Zwischenbericht 2014. Im Auftrag der Stadt Heidelberg. Passivhaus Institut, Juli 2015; dieser Bericht kann kostenlos beim Passivhaus Institut bezogen werden.
[PHPP] Passive House Planning Package. Passive House Institute, 1998 - 2015
[Reiß/Erhorn 2003] Reiß, Johann und Erhorn, Hans: Messtechnische Validierung des Energiekonzeptes einer großtechnisch umgesetzten Passivhausentwicklung in Stuttgart-Feuerbach, IBP-Bericht WB 117/2003, Fraunhofer-Institut für Bauphysik, Stuttgart 2003.
[Schnieders/Feist 2001] Schnieders, Jürgen; Feist, Wolfgang; Pfluger, Rainer; Kah, Oliver: CEPHEUS - wissenschaftliche Begeleitung und Auswertung, Endbericht, Projektinformation Nr. 22, 1. Auflage, Passivhaus Institut, 2001
[techem 2014] Techem Energy Services: Energiekennwerte 2014. Hilfen für den Wohnungswert. Eschborn, 2014
[Treberspurg 2010] Treberspurg, Martin; Smutny, Roman; Grünner, Roman: Energy monitoring in existing Passive House housing estates in Austria, proceedings of the 14th Passive House Conference, pp. 35-42, 1. edition, passive house institute, Darmstadt 2010