Use of PHPP and quality assurance

PHPP

The Passivhaus Planning Package (PHPP) is a very useful and powerful design tool, but it is easy to misinterpret the conventions, giving erroneous results. Avoiding these simple mistakes can reduce the need to find additional energy savings late on in a project. In a worst-case scenario, such mistakes might mean that a project cannot achieve certification. Training in the use of PHPP is strongly recommended, in order to be fully competent with the software.

Be conservative with values, as the thermal performance of elements very rarely gets better during design development. Optimistic inputs will be a problem later!

Entering the altitude of your site is important. Most of the data sets are from locations less than 50 metres above sea level, and if your site is significantly higher than the weather station this could easily add 1 kWh or more to the heating...

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It is easy to make mistakes with any modelling software, so having a robust QA procedure within your organisation is key. Ideally there will be someone who can look over your PHPP on a regular basis. Clear mark-ups of treated floor area, heat...

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The shading sheet is probably the trickiest within PHPP to get right, and it’s worth reading the PHPP manual carefully so you understand the instructions, especially about averaging reveal figures. It’s not sensible to be overly conservative...

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MVHR - Cre8 Barn, Green Building Store

PHPP generally assumes a ventilation rate of around 0.3 air changes per hour (ACH), which is based on German property sizes and occupancy rates. For most UK homes, which are smaller and more densely occupied, higher ventilation rates are...

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Unlike the UK’s National Calculation Methods (NCMs), such as SAP and SBEM, where each rough opening can be considered as one window, PHPP needs accurate window entries, which count each casement separately. Entering two adjacent window...

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Heat loss areas in Passivhaus are measured to the outside of the thermal envelope. This can be less straightforward than the SAP internal measurement methodology, as what constitutes the outside of the thermal envelope may not be immediately...

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Passivhaus experts Nick Grant and Alan Clarke have written a paper in which they examine the effect of internal heat gain assumptions across a range of building sizes and usage.

One of the ways in which PHPP has closed the performance gap between modelling and reality is to assume low...

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