Passivhaus
A comfort balance
A physics model
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The passivhaus planning package is a spreadsheet modelling tool that is more sophisticated than SAP allowing the design team and client to consider the design variables that matter, but simple enough to be understood by all parties. Using it should build our understanding of how the building physics is performing within your home and allow us to analyse and compare different measures.
Passivhaus Planning Package takes into account how your building is performing holistically and in some detail, and although no model can accurately predict how a building will be used, it is backed up by 15 years of real building performance evidence and designed by a physicist to show the balance of energy demand and gain within a building. Although the package has a clear structure this can provide a more flexible environment to try new methods and prove them within the model.
Passivhaus, (unlike some other energy models), is also a rigorous comfort standard, so it’s methodology should provide the following
No draughts - low airtightness mean less uncontrolled air infiltration which will be most obvious on cold windy days and less active on still summers days.
No cold spots - the low u value of the windows will be a change from standard windows which are significantly cooler than the rest of the room creating a reverse radiator drawing heat away from the body and meaning that spaces away from windows are more thermally comfortable.
No overheating - Overheating can be caused by inadequate insulation, and unshaded glazed areas facing the summer sun. The PHPP produces a warning if the indoor temperature exceeds 25 degrees for more than 10% of time occupied for the year. This includes internal gains from people and appliances, ideally we would be around 5%.
Comparatively Passivhaus is a physics model of a comfort standard for a building, whereas SAP is used to estimate fuel bills and CO2 emissions, therefore if you are looking to model your own home and optimise improvements PHPP is a much better tool to do so.
Although your house will not meet the passivhaus standard for new build or Enerphit, we still believe it will be valuable to model it within the Passivhaus Planning Package and have the principles of passivhaus at the forefront of our thinking. We have modelled what it would take to meet the Enerphit standard and outlined the reasons why it has not been targeted here.