PHPP - validated and proven in practice

Comparison with measured data

In the context of scientific monitoring, measured results from several hundred objects were compared with calculated results using the PHPP and dynamic simulations.

Of significant importance was the CEPHEUS Project within the framework of the Thermie Programme of the European Commission, in which urban settlements and larger building projects in the Passive House Standard were built and monitored scientifically in 14 European locations.

This project demonstrated that the thermal characteristics of buildings - even in the case of Passive Houses - could be reproduced with a high degree of accuracy using the energy balancing software programme PHPP. This is especially applicable in the case of the specially developed method for calculating the heating load.

The following illustration shows the results of a comparison of measurements and PHPP calculations for different urban settlements. Of particular interest is the fact that although there is always a high (relative) user (statistical) spread, the project planning results correlate excellently with the average measured results; - incidentally this was true for all building standards.

Figure 1:
Comparison of measured consumption (statistical data) with the PHPP calculation.

It is only possible to compare average measured results from sufficiently large statistical samples because individual consumption values fluctuate too much on account of the different user behaviours. The average values match the PHPP results almost exactly.

It is surprising that the results of the average measured values agree so well with the PHPP calculation. This is probably coincidental, because neither the accuracy of the measurement nor of the calculation is very high. Nevertheless, the depicted values are actual measured data - and the calculated results are those which were computed before the start of construction and already published before completion of the buildings.

Mitchell and Natarajan investigated a large sample of built passive houses build in the UK [Mitchell 2020]. They also compared these monitoring results with PHPP calculation, the results corroborate the analysis given here.

We often get the question, why there is such a huge fluctuation of the energy demand between different users: This is actually the case for all energy standards and not specific for energy efficient buildings - and it does not matter much in the case of passive houses, because even the highest consumption is still very small.

More accurate than conventional methods

The PHPP was systematically developed by adjusting the utilisation function to match the results of dynamic simulations [AkkP 13]. All simulation models that were used had been previously validated in measurements of completed Passive Houses. Adjustments were made for the Passive House standard – i.e. for buildings which require very little energy for heating. Here, the calculation with the PHPP varies slightly from that of the international ISO 13790 standard (European EN 832). However, the variation is not significant for ordinary buildings – it only affects buildings with extremely long time constants where ISO 13790 (EN 832) appears to be too positive.

The PHPP uses boundary conditions that are significantly different from other calculation procedures (e.g. the energy savings ordinance EnEV which is applicable in Germany). There are important reasons for these differences which are discussed in detail in [Feist 2001]:

  • In residential buildings with efficient household appliances, values of about 2.1 W/m² (±0.3) for internal heat sources are realistic during the heating period (rather than 5 W/m², as frequently assumed). The PHPP includes a calculation sheet which allows for more accurate determination of the internal heat sources of a specific building project. Assuming unrealistically high internal heat gains would result in unrealistically low values for energy use, suggesting that very low or even zero-energy houses are possible with moderate building standards. Practice has shown that this not true.
  • Realistic shading factors and dirt which is always present on surfaces should be taken into account for the calculation of solar gains.
  • Overall temperature correction factors are often set too low for well-insulated buildings: e.g. for top floor ceilings, realistic values for top floor ceilings are in the range of 1.0 rather than 0.8.
  • The airtightness value that is actually achieved, i.e. the measured n50 value must be assumed for the “additional air exchange rate due to leaks and window opening” - as is done in the PHPP and in DIN EN ISO 832.

These and other details lead to differences in calculation results based on the standard and the PHPP which are rather significant for energy efficient buildings. Since the algorithms in the PHPP have been developed and validated for energy efficient buildings, it provides more accurate results here than conventional calculation methods.

PHPP for exisiting buildings

PHPP was originally developped and validated for the design of energy efficient buildings with low energy demand. The question arises whether the same method and tool is also applicable and reliable for less efficient buildings, or even existing buildings with very high energy demand. This question was adressed as part of the EuroPHit project. A comparison of PHPP results with results from dynamic simulations revealed that, although some algorithms were developed with highly efficient, well-insulated buildings in mind, the PHPP can be used also for buildings with high energy demand with sufficient accuracy. The full report “Optimisation of the PHPP for old buildings with high energy consumption” can be downloaded from the EuroPHit website here.

Cooling Energy Algorithms

With the application of passive houses also in hot and huinid climates of planet Earth, algorithms for the claculation of the annual cooling energy and the cooling loads were required. This have also been validated against results of dynamic building simulations, documented in cooling energy.


Figure 2:
Example of a PHPP balance sheet for a terraced Passive House unit.
The annual heating requirement of 12 kWh/(m²a) meets the Passive House requirement.

Source: [AkkP 20]

Figure 3:
PHPP – monthly heating balance
for the example terraced house unit.

Source: [AkkP 20]
Figure 4:
PHPP – annual heating balance (sum of
monthly balances) for a terraced Passive House.

Source: [AkkP 20]

Solar gains and internal heat sources make for a greater share of heat gains than heating energy (column on the right).


[AkkP 5] Energiebilanz und Temperaturverhalten; Protokollband Nr. 5 des Arbeitskreises kostengünstige Passivhäuser, 1. Auflage, Passivhaus Institut, Darmstadt 1997
Energy balances and thermal characteristics; Protocol Volume No. 5 of the Research Group for Cost-effective Passive Houses, first edition, Passive House Institute, Darmstadt 1997
(only available in German)

[AkkP 13] Energiebilanzen mit dem Passivhaus Projektierungs Paket; Protokollband Nr. 13 des Arbeitskreises kostengünstige Passivhäuser, 1. Auflage, Passivhaus Institut, Darmstadt 1998
Energy balances with the Passive House Planning Package; Protocol Volume No. 13 of the Research Group for Cost-effective Passive Houses, first edition, Passive House Institute, Darmstadt 1998
(only available in German)

[AkkP 20] Passivhaus-Versorgungstechnik; Protokollband Nr. 20 des Arbeitskreises kostengünstige Passivhäuser, 1. Auflage, Passivhaus Institut, Darmstadt 2000
Passive House building services; Protocol Volume No. 20 of the Research Group for Cost-effective Passive Houses, first edition, Passive House Institute, Darmstadt 2000
(only available in German)

[Feist 1994] Thermische Gebäudesimulation; 1. Auflage, 366 Seiten, 1994 (Link zum Simulationsprogramm DYNBIL: Dynamische Simulation) Thermal building simulation, first edition,1994 (link to the article Dynamic Simulation)

[Feist 2001] Stellungnahme zur Vornorm DIN-V-4108-6:2000 aus Sicht der Passivhausentwicklung, CEPHEUS-Bericht, 1. Auflage, Passivhaus Institut, Darmstadt 2001
Statement regarding the Prestandard DIN-V-4108-6:2000 from the Passive House perspective, CEPHEUS Report, first edition, Passive House Institute, Darmstadt 2001

[Mitchell 2020] Mitchell, Rachel and Natarajan, Sukumar: UK Passivhaus and the energy performance gap; Energy and Buildings, Volume 224, 1 October 2020, 110240

[PHPP 2007] Feist, W.; Pfluger, R.; Kaufmann, B.; Schnieders, J.; Kah, O.: Passivhaus Projektierungs Paket 2007, Passivhaus Institut Darmstadt, 2007
Passive House Planning Package 2007, Passive House Institute, Darmstadt 2007

See also

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