The UK no longer just cool
A Passivhaus takes into consideration its local climate and the whole of the UK had a cool-temperate climate. Revisions to the newest version of PHPP 9 have seen some changes to climatic data, which have had implications on climate classifications within the UK.
- The selection of the climate data sets has been restructured. Quality approved climate data sets for certification are identified by a specific ID number.
- The climate data sets have been supplemented with information about the regional availability of renewable energy sources (PER factors).
- A climate data tool allows the search for the closest geographical climate data sets stored in PHPP. With this tool you, can retrieve global climatic data (except for Antartica) in the PHPP format, which is based on satellite data obtained from NASA Langley Research Centre Atmospheric Sciences Data Centre POWER Project, assessed and formatted by the Passivhaus Institute.
As the climate zone is now determined in PHPP based on individual climate data sets, locations in the UK now range from cold, cool temperate and warm temperate climates which can be seen on the Passivhaus Institute climate map below:
- The majority of the UK still falls within a cool-temperate climate. (Navy dots)
- Cold temperate locations can be found in Scotland. (Blue dots)
- Warm temperate climates can be found in the South e.g. Cornwall. London is included in this zone due to the urban heat island effect. (Green dots)
The Passivhaus Institute (PHI) also states the following warning:
The original satellite data have a resolution of one-degree latitude (111 km) and one-degree longitude (~79 km @ lat 45° [111 km * cos lat]), intermediate data are interpolated. Although a validation of each individual data set has not been performed, application of the data for orientational calculations can be recommended. Major inaccuracies may occur particularly in mountainous and coastal regions.
The last sentence is of particular interest to the UK's island typography which has a lot of coastlines! Data is also affected by altitudes, so some areas may be located in both warm and cool temperate zones depending on how high above sea level they are located. Eco Design Consultants discuss this further here.
Less insulation will be required in the warm temperate zones, which could improve affordability in terms of capital costs, but more attention will be required on overheating risks with cooling/shading strategies playing a greater role.
- Cool Temperate Zones – UK window certification requires insulated frame due to -16C external design temperature.
- Warm Temperate Zone – WARM, window certification satisfied with uninsulated frame due to -7 C external design. temperature.
The most significant impact will be felt on retrofits aiming for the EnerPHit standard. The map on the right, created by PHT member Eco Design Consultants, shows the changes in space heating demand for warm temperate zones. EnerPHits in London will need to meet the 20kWh/m2a target, along with other locations further south.
It will be interesting to see if the changes will help the uptake of the higher classes, Plus and Premium, in the UK.
At the moment, in England, we are tending to use the space heating demand target rather than the certified components route to EnerPHit because non-certified windows, that are currently often more affordable, are adequate for our cool temperate climate in terms of comfort and hygiene. This could change if parts of the UK are now declared a warm temperate climate.
Pete Warm, WARM
Implications for the UK
Older Versions of PHPP
PHT Associate Director, Kym Mead says there is an ongoing ‘grandfather’ clause, if a building has been designed in an older version of PHPP then it can be certified using the said PHPP.
As I certifier I would always encourage the designer to stress test the design in the new PHPP– especially for overheating!
Kym Mead, Passivhaus Trust
PHI have been working on the robust climate data for some time and UK certifiers have recently funded further research. Feedback on how the criteria works in real-world conditions in various countries is very important for PHI, and will be integrated into ongoing further development of the criteria. PHT members can access details via Passipedia. CIBSE and PHI are currently discussing an anomaly within the Southampton data. Useful links are listed below.