stratification effect

What difference have destratification fans made to Selly Oak Friends Meeting House?

On 16 October 2023 we held our first Birmingham Green Doors visit to a non-domestic building – Selly Oak Friends Meeting House.  This blog is my account of what we have learned so far.  There is still more learning and monitoring to be done.

We heard from Clare Peat (Meeting House Manager) about how work the Quakers had done over the years to lower their carbon footprint.  They have received advice and support from various sources including Tim Richardson who did their quinquennial building report, and my good self on behalf of the Footsteps project.  Members of the Quaker community have undertaken a lot of work themselves including pipework insulation, draught-proofing, loft insulation.

We heard from John Ironside about their destratification fans.  I advised them in 2022, through the Footsteps programme, that there was a destratification effect in their worship area due to its high ceilings.  Convection makes warm air rise to the top and centre of the Meeting House, displacing colder air, which then falls to ground level, especially at the sides of the building.  This means that people feel cold in winter, and in particular there is a temperature differential between their head and their feet, which makes people feel uncomfortable.  The stratification effect also wastes heat.  I used thermography to demonstrate the existence of a stratification effect.

I advised them to consider destratification fans to reverse the stratification effect, make the place warmer and save energy.  A few years ago I met Seamus Treanor, an energy expert, who has done a lot of work on destratification fans in places of worship.  Selly Oak Friends went to see Seamus at St James’ Church, in Barton-under-Needwood, Staffordshire, and he showed them two methods of destratification.  The first one was where you have a series of smaller downdraft fans sited about 4 metres high in the nave, to reverse the convection, through a fairly linear movement of air.  This was the method I was most familiar with.  When we arrived at Selly Oak Meeting House on the cold evening of 16th October 2023 for the Birmingham Green Doors visit, I was surprised not to see destratification fans at 4 metres high.  I looked for them and I could not see anything – and I certainly could not hear anything.  What came as a surprise to me and everyone present was that following advice from Seamus, John and Clare had gone for another method of destratification.  This involves using a larger fan at ground level but at a very low speed.  Instead of reversing the convection of hot air, it displaces the destratification effect, and creates a continuous movement of air circulating around the room – more of a non-linear movement of air.  This gives a more even distribution of heat.  It was certainly warm and comfortable in there.  I got my infra-red thermometer out (as did Harriet Martin of Cotteridge Quakers who was also present) and we took readings which demonstrated that the distribution of heat was more even with only a very slight stratification effect.

Thermal image of stratification

Thermal image showing destratification effect in a place of worship (a Hindu Mandir in a converted  cinema)


This approach to destratification is also good news from a planning point of view.  You don’t need faculty approval for this type of fan, as it’s not fixed to the building fabric.  At Selly Oak Meeting House they have hidden it behind the piano and plugged it into the wall.  They are going to add a timer to enable Clare to control when it’s on and off.  A smart plug would give greater control.  In a listed building, you would not need faculty approval or planning permission for an appliance of this type.

A number of people present were considering destratification fans in their buildings.  Some of them had heard differing stories about their effectiveness.  This is understandable.  I have seen poorly designed destratification fans dating from the mid 20th century.  Destratification fans are like any other energy saving measure – you can’t just chuck them in and hope for the best.  They need to be properly thought through.  What Selly Oak Friends have done has the potential to change the way we think about destratification fans in places of worship with ceiling heights of more than 4 metres.  What I am going to do next, with the help of Selly Oak Friends, is to assemble data which will show us what impact they have made on energy use and greenhouse gas emissions.  I will distribute these when available.  I am not aware of any written case studies of destratification fans in this type of building.

I was also impressed with the changes that they had made to their existing heating controls.  In the medium term they have plans to improve insulation and to move from gas to a heat pump.  But what this example shows is that low cost measures (pipework insulation) and medium-cost measures (improved heating controls; improved lighting controls; destratification fans) make a difference and can be achieved in the short-term.  This means you can make real progress, and keep bigger measures (insulation, heat pumps, solar) as long-term goals and not get dazed by them.

Thank you to Selly Oak Friends for hosting, and for tea and biscuits!

Information on the fan in use at Selly Oak Friends Meeting House –

ebm-papst EC Aura Floor, Heavy Duty Fan 7250m³/h 230 V with plug: Type F – Schuko plug 

You don’t need to hard-wire this type of fan so you don’t need an electrician.  If you are installing destratification fans at a 4m height, (see diagram below of a suggestion I made to St Mary and St Margaret’s Castle Bromwich – photo from their Facebook) then they do need to be hard-wired and an electrician can do this – you don’t need a specialist installer.

destratification fans location

Suggested location of fans in green

destratification fans location

Suggested location of fans in purple


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