PHPP - the Passive House Planning Package

The Passive House Planning Package (PHPP) is an important tool for designing Passive Houses consisting of a spreadsheet workbook and a manual. The latest revised edition of the 2007 version has been available since spring 2010.

The Passive House Planning Package (PHPP) provides everything needed to design a properly functioning Passive House including tools for:

• calculating energy balances (including U-value calculation)
• planning the windows
• designing the comfort ventilation system
• determining the heating load
• estimating the summer comfort
• design the heating and hot water supply

It also provides a variety of other useful tools for the reliable designing of Passive Houses as well as:

• verification for Passive House funding (e.g. for low-interest loans available in many countries)
• a simplified verification method (based on the German Energy Saving Ordinance)
• a detailed handbook that provides not only a detailed explanation of the PHPP calculation method but also important details for the construction of Passive Houses – the Passive House construction manual par excellence.
• an example project calculated in PHPP: Residential buildings
  

For the very first Passive Houses, it was essential to use numerical simulations with high temporal resolution for dimensioning the buildings. Calculating the energy balances of buildings with very low energy consumption is a complex task. Existing regulations and standards such as the ones applicable in Germany have proven to be too inaccurate in the past – and haven’t been improved since.

The behaviour of buildings can be predicted very accurately using a simulation that is based on the fundamental laws of physics. The only problem is that the input data required for dynamic simulation programmes are very comprehensive. Our computer model for the Passive House in Darmstadt Kranichstein, Germany requires over 2,000 independent data entries (without the climate data set). If the simulation is to provide reliable results, these data must be correctly determined based on the actual geometry of the building.

Comparing the simulation and measurement results shows that such a model can provide accurate results ([AkkP 5] , see fig. 1), but not without a lot of effort. Besides, not all required data are equally important. Even so, inaccurate values for “unimportant” data can lead to incorrect results.

fig. 1: Comparison between measurement and simulation results in the Darmstadt Kranichstein Passive House project. (simulation programme used: DYNBIL; see Dynamic simulation of a building's thermal performance; published in [AkkP 5] ).

By comparing different simulation models we can pinpoint the key data required to prepare accurate balances. This way, we can apply a simplified model which will pair reliable results with justifiable effort for data acquisition [Feist 1994] . The methods for admissible simplifications are described in the publication [AkkP 13] . It is surprising that even a rather simple model (see fig. 2) will provide a level of accuracy which is sufficient for practical planning purposes by

• treating the whole house as one zone
• calculating monthly energy balances instead of using time-resolved dynamic simulation

fig. 2: Comparison between simulation (DYNBIL) and PHPP results (monthly method according to the international standard, ISO 13790 and annual method) demonstrating a high level of agreement between the simplified stationary and the dynamic method. It is important to ensure that all methods are based on identical input data.

A concise calculation process is not the only advantage of this simplified method:

• Less effort is required for data acquisition (as only the building envelope and ventilation data need to be ascertained),
• Sources of errors are minimised and the calculation process can be verified more easily. (Inspection engineers dread having to check the accuracy of a set of data input for a numerical simulation in the course of quality assurance for a building)
• Focus on the really important influencing factors and
• Inclusion of all these important influencing factors.
  

To briefly discuss this last point: Most highly developed simulation programs are very accurate with respect to certain physical processes (e.g. in transient thermal conduction or radiant heat exchange) but they simplify the model at other points (e.g. angle-dependent radiation transmission through glazing, or prevention of solar radiation by balcony overhangs, lintels etc.). So far, not one programme has managed to deal with “all” relevant processes “physically, reasonably and accurately”. Even in the future such a programme would have to be rather complex, thereby creating more potential for errors.

Of course, each simplification implies less accuracy – but every incorrect data entry in a complex model also leads to a loss in accuracy. And, pragmatically speaking, the maximum accuracy of any calculation for the (weather dependent!) thermal behaviour of a building is limited in any case. We are definitely not arguing against using simulation programmes; on the contrary, this the only correct scientific approach. However, in the practical planning process for the established building concept, a simplified calculation method adapted optimally to the individual task can even be more accurate due to fewer potential errors

The PHPP is a calculation tool which has been optimised for the construction of Passive Houses and has proven itself a thousand times over. It has been calibrated based on simulation calculations using complex dynamic models.

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 (see fig. 1). Adjustments were made specifically for the Passive House standard – i.e. for buildings which require very little energy for heating. The calculation with the PHPP varies slightly from that of the international ISO 13790 standard (European EN 832 standard). However, the deviation for ordinary buildings is not significant – it only affects buildings with extremely long time constants in which case ISO 13790 appears to be too positive.

Subsequently, the results of the PHPP calculation have been repeatedly compared with measurement results from sufficiently large samples of built Passive Houses, (see fig. 3). This comparison has always shown a very good correlation.

fig. 3: Comparison between measurement results (statistic data) and PHPP calculation results. It is important to compare average values from a sufficiently large sample since individual values will vary significantly due to differences in user behaviour. The average values correspond rather precisely with the PHPP results.

The PHPP uses boundary conditions that are significantly different from other calculation procedures (e.g. the Energy Savings Ordinance 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 a more accurate determination of the internal heat sources of specific building projects. 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.
• An average indoor temperature of 20°C can be assumed to be more realistic than 19 °C.
• Realistic shading factors and dirt which is always present on surfaces should be taken into account for the calculation of solar gains.
• 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 Energy Savings Ordinance which is applicable in Germany (EnEV) generally assumes an “additional air exchange rate due to leaks and window opening” of 0.15 h^-1 for exhaust air systems and 0.2 h^-1 for balanced ventilation systems with heat recovery – both values are too high. Instead this value must be based on the actual level of airtightness , i.e. the measured n₅₀-value, as is the case in the PHPP and in ISO 13790.

These and other details lead to differences in calculation results which are rather significant for energy efficient buildings.

Several PHPP calculations are based on the assumtion that the latitude specified in the Climate Data worksheet is located in the Northern Hemisphere. For locations in the Southern Hemisphere, two changes are required:

1. Change the climate data from the southern hemisphere for use in the PHPP
2. Mirror the location on the equator

In order to spare users the complex task of entering these changes manually, the Passive House Institute has developed a climate data tool for the adaptation of the relevant data to the Southern Hemisphere.

More than just an energy balance: The PHPP was not primarily developed for providing any kind of proof. Rather, the PHPP is a design tool allowing architects and specialist planners to skilfully plan and optimise their Passive House design. The PHPP contains tools for dimensioning windows (with regard to optimum comfort), the ventilation system (in terms of optimum indoor air quality with sufficient levels of humidity), and building services. The PHPP treats the whole house as a single unit, including the ventilation system and other building services. The PHPP manual doesn't just explain the data input for the worksheets, it also provides advice for the optimum (airtight, thermal bridge free and cost efficient) arrangement of building components, for the planning process and for the quality assurance.

fig. 4: 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.

fig. 5: PHPP – monthly heating balance for the example terraced house unit.	fig. 6: PHPP – annual heating balance (sum of monthly balances) for a terraced Passive House.

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

Here you will find background and further details on the individual sheets of the PHPP:

Areas
U-List
The overall heat transfer coefficient or U-value
Ground
Windows
WinType
Shading
Ventilation
Annual Heating Demand
Monthly Method
Heating Load
Summer
Shading-S
SummVent
Cooling
Cooling Units
Cooling Load
DHW+Distribution
SolarDHW
Electricity
Electricity Non-Dom
Aux Electricity
PE Value
Compact
Boiler
District Heat
Climate Data
Climate data tool for the Southern Hemisphere
IHG
IHG Non-Dom
Use Non-Dom
Data
Conversions

[AkkP 5] Energiebilanz und Temperaturverhalten (Energy Balance and Temperature Behaviour); Protocol Volume Number 5 of the Research Group for Cost-efficient Passive Houses, First Edition, Passive House Institute, Darmstadt 1997.

[AkkP 13] Energiebilanzen mit dem Passivhaus Projektierungs Paket (Energy balances using the Passive House Planning Package); Protocol Volume Number 13 of the Research Group for Cost-efficient Passive Houses, First Edition, Passive House Institute, Darmstadt 1998.

[Feist 1994] Thermische Gebäudesimulation (Thermal Simulation of Buildings); First Edition, 366 Pages, 1994 (link to DYNBIL simulation program: Dynamic simulation of a building's thermal performance)

[Feist 2001] Stellungnahme zur Vornorm DIN-V-4108-6:2000 aus Sicht der Passivhausentwicklung (Comment on the Prestandard DIN-V-4108-6:2000 from the Passive House development viewpoint) , CEPHEUS-Report, First Edition, Passive House Institute, Darmstadt 2001.

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