Energy performance of modern conservatories
Quinten Babcock and Steve Irving, FaberMaunsell Ltd, St Albans.
Conservatories are a very popular home improvement. A decade or so ago, they were seen as a key
element in the design of passive solar houses, but more recently, the accepted view seems to regard
conservatories as energy liabilities1. Ironically, over that same period, the thermal performance of
conservatories has improved significantly. The project on which this paper is based was aimed at
trying to understand the energy performance of modern conservatories, and to develop guidance on the
important parameters that influence energy performance.
Two aspects of the performance of conservatories are reported here. Firstly, winter performance,
where the balance between passive solar benefit and the heating requirements for extended
conservatory occupation is assessed, along with the effects of style, size, and heating setpoint.
Secondly, the increased prevalence of portable domestic air conditioners has raised concerns over a
possible trend towards active cooling of conservatories. Therefore, the relative effectiveness of
different strategies for providing summer comfort is also reported.
Conservatories are very popular spaces, because they provide high levels of natural light, offer
excellent views into the garden and thereby create an attractive buffer space between house and
garden. In 2001, approximately 170,000 new conservatories were built in the UK2, and the market is
expanding rapidly. The energy flows in conservatories are very complex (see example in Figure 1),
involving the usual conduction and ventilation and heating system energy flows, coupled with very
large variations in solar gain all within a light-weight structure. In common with most issues related to
dwellings, the way the occupant uses the conservatory is very variable, and has a big impact on energy
performance. The coupling between the conservatory and the house is als