Climate Control in Glasshouses

We were pleased to welcome Martin Emmett, from the University of Reading, who gave an excellent and thought-provoking training day for us, full of practical information.

The climate in a botanical greenhouse varies across the floor plan and changes with time of day and season. Understanding these differences and using them in planting schemes and the management of the climate-control system present opportunities for energy saving and more effective displays.

After talks and discussion on the basic principles of heat transfer and humidity in glasshouses, ways of monitoring microclimates were considered. The importance of positioning and regular maintenance of aspirated screens and other equipment was emphasised.

Martin explained how to record a temperature profile across a glasshouse using an infrared thermometer and plotting the results in a colour-coded table using Microsoft Excel 2007. Kate Pritchard and her glasshouse staff had been asked to take readings at various times in the Palm House at Oxford Botanic Garden using this method. They marked a grid in the glasshouse and placed blank labels (marked with a coloured spot so that they were easy to find) at regular intervals so that all readings were from the same type of surface. The results revealed some hot and cold spots that they had not been aware of and confirmed others that they had suspected.

Results of temperature profile from Oxford glasshouse:

9 am, 17th April 2008
11.15 am, 17th April 2008
1 pm, 17th April 2008
3 pm, 17th April 2008

The cost of time spent on temperature profiling and monitoring equipment could be more than covered by savings in subsequent heating costs in response to the information gathered. After a tour of the glasshouses and a demonstration of taking temperature readings in the Palm House, action points for climate control under glass were discussed. Martin would like to publish some information on temperature profiling in various types of botanical glasshouse. If you do use the technique he described, he would be interested to see the data and possibly use it in a publication — he will try to give a constructive response to anything submitted (please email him m.r.emmett at The data would need to be arranged according to the floor plan of the glasshouse. He suggested that it would be helpful for PlantNetwork to produce guidelines for architects on system requirements for plants to be grown in innovative structures.


ACTION POINTS from the meeting

  • Aspirated Screens (or Thermometer Stations)
    • Confirm suitable positioning.
    • Have an auditable maintenance schedule (including thermocouple or bulb cleaning).
  • Temperature Profiling / Mapping
    • Consider purchase of an IR Thermometer and Excel 2007.
    • Identify suitable sample points.
    • Schedule times across the year for mapping exercises.
  • Climate Control Systems Review
    • Create a protocol for visually confirming correct system operation (including thermometer stations).
    • Set up a maintenance audit system for heating and ventilation equipment.
    • Review the contribution lighting systems are making to plant temperatures.
    • Review the use of water features as heat stores
  • Plant Management
    • Have a proceedure for referencing phenotype of glasshouse specimens against wild specimens (choose some key indicator species).
    • Staff Training on the impact of high humidity / condensation on plants.
  • Climate Management
    • Review existing climate control technology – does it need upgrading.
    • If you have an older system; are seasonal hysteresis (or P-band) settings being applied.
    • Consider application of a temperature integration programme.
    • Review the need for acclimatisation proceedures if radical changes to temperature set points are made.
    • Have a clear and understood emergency proceedure for heating system failure.
  • General – PlantNetwork
    • Produce guidelines for architects on system requirements for innovative structures.

Our thanks to Martin, and to Kate Pritchard and Louise Allen and their staff for a really helpful and interesting day.