There has ben some significant testing carried out by the Fire Protection Association on behalf of Historic England and NFU Mutual Insurance. They have updated the information on heat transfer from chimneys in thatched properties. Point number one in the executive summary of the FPA report reads:
“The widely accepted idea that heat transfer by conduction (i.e. “Heat Transfer Theory”) is the predominant mode of fire raising in thatched buildings is not supported by the data.”
You can find the full FPA report here at the Thatch Advice Centre.
Please also find the FPA consumer guidance download here – https://www.thatchadvicecentre.co.uk/wp-content/uploads/2018/08/FPA-Guidance.pdf
Our thanks to the Thatch Advice Centre for keeping us posted on these matters.