The 2011 Energy Follow-Up Survey (EFUS) collected data on how households in England use and heat conservatories. The survey interviewed 2616 households, providing a nationally representative sample of the 21.9 million households in England. The results indicate that around 18% of households have a conservatory, equating to around 4 million conservatories nationally.
Key findings on heating and usage:
- Around 77% of conservatories have some form of heating. Just over half (55%) are connected to the central heating system and 42% have portable electric heaters.
- In winter, 56% of heated conservatories are used daily. Only 20% are never heated in winter.
- 45% of heated conservatories are heated to the same temperature as the house. 39% are heated to a lower temperature.
- In summer, 91% of heated conservatories are never used.
- The most common rooms that conservatories are connected to are living rooms, kitchen/diners and dining rooms. These are typically heated rooms.
- 91% of conservatories have a separating door to the house that can be closed.
- In winter, 83% of households keep this door closed all day or only open it when the conservatory is in use. This is mainly to retain heat in the house (88% cited this reason) and for security (17%).
- In summer, 81% of households leave the door open for at least part of the day, mainly for convenience (40%), to allow heat into the house (33%) and to make rooms feel more spacious (22%).
- In winter, 59% of conservatories are used less than once per week. But 23% are used daily.
- In summer, 70% of conservatories are used daily, with only 11% used less than weekly.
- Daily winter use is predominantly in the afternoon (65%), morning (47%) and evening (43%).
Implications for energy modelling:
- SAP currently ignores conservatory energy use if it is thermally separated from the house. But most are heated despite separation. SAP should be updated to account for heated conservatories.
- Most conservatories are heated to the same or lower temperature than the house. SAP could assume a slightly lower temperature for conservatories.
- Building regulations exempt conservatories from efficiency requirements if heating is not extended into them. But portable heaters are commonly used. Consideration should be given to including conservatories where heating can be provided.
Gas consumption analysis:
- Median gas use in homes with heated conservatories was 18,200 kWh, compared to 13,400 kWh in homes without.
- But homes with conservatories tend to be larger. When analysed by floor area, those with conservatories are no more likely to be in the top 10% highest gas-consuming homes than those without.
- A multivariate analysis is needed to fully understand the link between conservatories and gas consumption.
In summary, the EFUS provides comprehensive new evidence that conservatories are commonly heated in winter, despite assumptions that they are unheated extensions. The frequency of heating, and temperatures used, are now better understood. Keeping heat in conservatories is much easier with a conservatory roof replacement
This has implications for energy models, which may currently underestimate heating use in around 4 million English homes with conservatories. Revisions should be considered to SAP and building regulations to account for typical conservatory heating patterns observed in this survey. Further analysis of the gas data would also help quantify the scale of additional energy use linked to heated conservatories.