Table of Contents
PHPP calculations in hot and humid climates
The [PHPP] (Passive House Planning Package) is an indispensable design tool for planning Passive Houses. Since its first publication in 1998 the software has been developed continuously in order to fulfil the increasing demand for more complex specifications. The software was originally developed with a focus of optimising the energy efficiency of residential buildings in cool-temperate climates where the space heating demand is dominant and summer comfort is less of a concern. In this context it has proved its worth in thousands of successful building projects. Meanwhile, the Passive House concept is also being applied in hotter and more humid climates, where the energy demand for cooling becomes more important than space heating. Though the PHPP V7(2012) and earlier do include calculation algorithms for cooling, these were never systematically checked for reliability.
Recent projects in Mexico in collaboration with GIZ / GOPA were thus taken as an opportunity to review the PHPP algorithms for active cooling in hot and humid climates. The aim was to develop a new and reliable energy calculation tool for Mexico (DEEVi, based on PHPP algorithms). As a prerequisite, the applicability of the PHPP for active cooling dominated situations was to be investigated and, where necessary, improved. The approach taken was a detailed comparison of PHPP results of a simplified building model with the equivalent reference values determined by means of a dynamic hygrothermal simulation with the software DYNBIL. The main influencing parameters for the cooling demand were varied consistently in both programs, their effect on the results analysed and, if required, the PHPP algorithms adjusted accordingly. The results presented in this report (section 3) show the active cooling demand as calculated with the modified PHPP algorithms as implemented in the upcoming release version PHPP V8.1 (2013).
In climates in which the Passive House concept can be reached without the need for active cooling the frequency of overheating is used as an indicator to assess summer comfort. Though the corresponding algorithms were also updated in the context of the DEEVi developments and thus in the newest PHPP release, this aspect shall not be part of the report at hand.
Summary and Outlook
The useful energy demand calculated with the new PHPP algorithms are in very good agreement with the dynamically calculated values for both sensible and latent cooling under all considered boundary conditions. The algorithm modifications and additional features undoubtedly increase the PHPP’s international applicability, as highly relevant humidity related aspects are now included in the energy balance. The results shown in this report clearly demonstrate that the PHPP can be used as a reliable planning tool also in hot and/or humid climates. The next step following this systematic result comparison is a validation by means of calibration with measured data from actual projects.
[PHI 2013] Final Report of the development of the DEEVI - Diseño Energéticamente Eficiente de la Vivienda, Passive House Institute, Darmstadt, 2013.
[PHPP] Passive House Planning Package, Passive House Institute, Darmstadt. Version 7 (2012) and Version 8 (to be released 2013)
[Schnieders 2009] Schnieders, Jürgen: Passive Houses in South West Europe. 2nd, corrected edition. Darmstadt, Passivhaus Institut, 2009