The
Passive House Planning (Design) Package (PHPP)
includes:
 energy calculations
(incl. R or Uvalues)
 design of window specifications
 design of the indoor
air quality ventilation system
 sizing of the heating
load
 sizing of the cooling
load
 forecasting for summer
comfort
 sizing of the heating
and domestic hot water (DHW) systems
 calculations of auxiliary
electricity, primary energy requirements of such (circulation
pumps, etc.), as well as projection of CO2 emissions
 verifying calculation
proofs of KfW and EnEV (Europe)
 Climate Data Sheet:
Climate regions may be selected from over 200 locations in Europe
and North America. Userdefined data can also be used.
 ... and a lot more
tools useful in the design of passive houses, e.g. a calculation
tool to determine internal heat loads, data tables for primary
energy factors, etc.
 a comprehensive handbook,
not only introducing PHPP use, but also highlighting crucial topics
to be considered in Passive House design.
The
Scientific Background: Simulation Program Solidly Rooted In Principal
Equations of Physics
For the first Passive
Houses, it was indispensable to use sophisticated modeling, employing
many sets of highresolution dynamic data. Calculating the energy
balance of buildings with very low energy consumption is a demanding
task  existing codes and standards proved too inaccurate (in that,
little has changed to this day). The challenge: the input data for
an intermittent simulator routine are very extensive – our
computer model for Darmstadt Kranichstein requires over 2000 independent
input data (without the climatic data set). If the simulation is
to provide reliable results, these data must be in accordance with
the actual geometry of the building. This is indeed possible, as
we can see from the comparison between simulations and plotted actual
measurement data ([AkkP5] Fig. 2, above left).
The expenditure for such a model is extensive, and not all the necessary
data are of equivalent importance. Nevertheless, we have identified
in the meantime the critical factors for preparing reliable calculations
 with tools that are simple to use and with acceptable effort in
terms of data input. The technique for designing wellperforming
passive houses has now been tried, tested and optimized in thousands
of cases.
A
Pragmatic Solution: Simplified Model, Well Defined Input Data
In comparing different
simulation models and tools, we were able to distill which elements
are truly important. In this way it was possible to devise simplified
models to be used with an affordable effort and which still provide
reliable results [Feist, 1994]. The development of the simplifications
is published [AkkP 13]. It may be surprising, but accuracy sufficient
for practical planning purposes can be achieved using a quite simple
model. That is:
 treat the whole building
as one zone of energy calculation
 use monthly
energy balances in lieu of dynamic simulation with short
time steps.
(see fig.
3 in the column left hand side).
Transparency of calculation is not the only advantage. More importantly:
 Much smaller expenditure
on data acquisition (only the data of the building envelope and
of the ventilation have to be determined),
 The sources of errors
are reduced and it is simpler to inspect the data and the calculation
(a quality controller would be horrified to have to examine and
assure the propriety of a numerical simulation data set).
 The designer can concentrate
on the important variables…
 ...and can be sure
to include all of these in her/his design.
To briefly discuss this
last point: Most highly developed simulation programs are very accurate
with respect to certain of the physical processes (e.g. nonstationary
thermal transmission or for radiant heat transfer), but these models
serve to distort in other areas (e.g. angledependent radiation
transmission through glazing; the shading of solar radiation by
balconies, lintels, etc). So far, no single program has been able
to fully address all relevant processes to the exacting satisfaction
of physics. Even at future such a program would be highly complex,
which will create additional potential for errors.
Naturally, any such simplification
implies a lost in accuracy  but each datum that is not fully correct
when put into a complex model will also lead to losses of accuracy.
And, pragmatically viewed, the computational accuracy possible is,
at any rate, limited by the precedent case of data not predictable
with high accuracy – the weather! We do not argue here expressly
against the use of detailed simulation programs: On the contrary,
these programs are the only acceptable way for scientific research.
But for the practical purpose of building design, employing already
welltested building concepts, the use of simplified, optimally
adapted computing tools will reduce the probability of errors and
might therefore be even more accurate.
The tool optimally adapted
for the design of Passive Houses is the wellproven PHPP (Passive
House Planning Package). The PHPP has been calibrated with simulation
calculations using complex dynamic models.
Why is PHPP more
accurate for energy efficient buildings than other tools?
PHPP was systematically
developed by aligning the utilization rate function with the results
of dynamic simulation models [AkkP 13]. For this development only
such models were used as had been validated against monitoring results
of built passive houses (see fig. 2 in the left
column). By this method was the standard for Passive Houses aligned,
as well as a standard for buildings with low, but not as low, energy
requirement for heating. However, for such buildings the calculation
differs slightly from what is given in the European standard EN
832 (ISO 13 790). But the difference is not important for conventional
buildings  it is only of influence for buildings with very long
time constants. In this class of buildings the ISO 13 790 tourns
out to be a little bit too optimistic.
The results from PHPPcalculation
have been repeatedly compared with monitoring results of sufficiently
large samples of built Passive Houses (see fig.
4 on the left side). These comparisons have always shown a very
good correlation.
The PHPP clearly uses
boundary conditions that are significantly different from
the calculation process used for the German Energy Conservation
Ordinance (EnEV). There are important reasons for this  these are
discussed in detail in [Feist 2001] and given in short here:
 For internal heat
sources in residential buildings using efficient appliances,
during the heating season values of some 2.1 W/m² (±0.3)
are realistic (and not 5 W/m², as frequently assumed). In
the PHPP, there is an additional calculation sheet to determine
the internal heat sources of given building projects. However,
if internal heat gains are assumed to be higher than realistic,
this will result in significantly lower heating energy requirements
and may even lead to the illusion that a "zero heating house"
can be built with a building envelope of mediocre quality. Practice
shows this to be untrue.
 The average indoor
design temperature in German dwellings can be assumed to be 20°C.
This is more realistic than the 19 °C given in the German
ordinance. The PHPP user can adjust this indoor design temperature
to his or her specifications.
 To calculate solar
gains it is important to take into account realistic shading
factors (the environment, balconies, etc.) and also to account
for everpresent dirt and dust on surfaces.
 Temperaturecorrectionfactors
(Ffactors) very often were chosen too optimistically for superinsulated
buildings. E.g. for insulated ceilings under uninsulated roofing,
the Ffactor values are not in the range of 0.8, but nearer to
1.0.
 The assumption to
add an "additional air exchange rate" due to useropening
of windows is given by EnEV to be 0.15 h^{1} for exhaust
systems; 0.2 for balanced ventilation systems with heat recovery.
Those values are assumed far too high. To be correct, one needs
to base values on achieved airtightness; which means based on
actual measured n_{50}value, as in the PHPP and DIN EN
832 / ISO 13 790.
These and additional
topics result in differences in calculation results, which are significant
for energy efficient buildings.
More
than just an Energy Calculator
The PHPP was not primarily
developed just to calculate energy requirement verifications. Much
more, the PHPP is a designtool, which can be used by the
architect and the engineers to design and optimize their Passive
House project. In the PHPP they will find dimensioning tools for
the windows (with attention to optimal comfort), for the heat recovery
ventilation system (with attention to good indoor air quality and
sufficient relative humidity), for the mechanical systems and for
summer comfort. Within PHPP, the building and the mechanical equipment
are treated as one overall system.
The PHPPhandbook is
not restricted to explaining the use of the spreadsheets and the
compilation of the input data. Rather, the handbook gives advice
on how to optimize the design (e.g. how to build very airtight,
how to avoid thermal bridges, how to minimize construction costs).
All this is very useful during the planning phase and for quality
control work as well.
This
link leads to the main site of the Introduction to Passive Houses.

Author: Dr. Wolfgang
Feist, director of the PHI
Link
to the homepage of the
Passive House Institute:



Literature:
[AkkP 5] Energiebilanz
und Temperaturverhalten; Protokollband Nr. 5 des Arbeitskreises
kostengünstige Passivhäuser, 1. Auflage, Passivhaus Institut,
Darmstadt 1997 GERMAN (Link
zur Publikationsliste, PDF,
200kB)
[AkkP 13] Energiebilanzen
mit dem Passivhaus Projektierungs Paket; Protokollband
Nr. 13 des Arbeitskreises kostengünstige Passivhäuser,
1. Auflage, Passivhaus Institut, Darmstadt 1998 GERMAN (Link
zur Publikationsliste, PDF,
200kB)
[AkkP 20] PassivhausVersorgungstechnik;
Protokollband Nr. 20 des Arbeitskreises kostengünstige Passivhäuser,
1. Auflage, Passivhaus Institut, Darmstadt 2000 GERMAN (Link
zur Publikationsliste, PDF,
200kB)
[Feist 2001]
Stellungnahme
zur Vornorm DINV41086:2000
aus Sicht der Passivhausentwicklung,
CEPHEUSBericht, 1. Auflage, Passivhaus Institut, Darmstadt 2001
GERMAN (Link
zur Publikationsliste, PDF,
200kB)
An English version is
available:
[PHPP 2004] Feist, W.;
Pfluger, R.; Kaufmann, B.; Schnieders, J.; Kah, O.: Passive
House Planning Package 2004/2007, Passive House Institute
Darmstadt, 2004/2007 (Link: PHPPcontend).
A complex model, based on the fundamental physics of heat transfer
and suitable for systematic scientific research. The "circuit
diagram" shows a part (one room) of the DYNBILmodel used for
the Passive Houses in Darmstadt Kranichstein. Using this model the
fundamental research was done to develop the concept. And a comparison
of the accurate measurements, which took place in the realized building,
was made to the simulations later (fig. 2 on the
left side). This Model was also then used to calibrate the PHPP
calculation. (Click on the figure to show a higher resolution).
(updated: 20070526
Author: Wolfgang Feist;
The author thanks Katrin Klingenberg, Mike Kernagis and David Stecher
for doing extensive proof reading of this article.
© Passive House Institute; unchanged copy is permitted, please give
reference to this site) 