Where these numbers come from
- Measured: the design temperature, the degree days and the monthly means. All of it from one station, :station, over :years complete years.
- Assumed: everything about the building. The U-values are typical published figures for each construction era, not a survey of your house. Two houses of the same age and size can differ by a factor of two.
- No credit is taken for sunshine or for the heat given off by people and appliances. That is the EN 12831 convention, because the design condition is a still, dark night.
- This is space heating only. Domestic hot water is a separate load.
- This is a calculation, not a survey. Before spending money, have the building assessed.
- A city appears here only if a station within 50 km, and within 200 m of its elevation, has at least fifteen complete years of record. Where two cities share the nearest station they would carry identical numbers, so only the larger is published.
Sources
| Temperature, degree days, dew point | NOAA Global Summary of the Day, 1991–2020 (public domain) |
|---|---|
| Station positions and records | NOAA Integrated Surface Database station history |
| Cities, coordinates, local names | GeoNames (CC BY 4.0) |
| Heat loss method | EN 12831, simplified: transmission + ventilation at the design temperature |
| Design temperature statistic | 1st percentile of daily minimum temperature |
Coverage
1,583 cities, each backed by its own weather station within 50 km and 200 m of elevation, with at least fifteen complete years of record.