Insulation properties of thatch

Question:
The current recommendation for insulation in a standard roof is 10½ inches. I was wondering if this is the same for a thatched roof or is less insulation required because of the thatch?

Answer:
From the most up to date information we have the U value of a roof refers to its thermal conductivity, i.e. how quickly heat is lost from it, and is measured in watts per square metre per degree Kelvin.

The U value of 12 inches of water reed on a pitch of 45 degrees is about 0.35 W/sq m K. The current building regulations state that the U value required from a new roof is 0.25 W/sq m K. Therefore, on a new build, there would need to be some additional insulation under a twelve inch water reed thatched roof. However, thick thatch with multiple sparred layers will have a lower U-value. The U-value will also be affected by the roof space climate, for example, whether the roof space is well ventilated (draughty) or sealed, warm and snug.

Outside Halogen Security Lighting and thatch

Halogen security lights and internal spot lights can get very hot, very quickly. They are an acknowledge fire risk in conventional houses where they come into direct contact with drapes inside the house (the fire in Windsor Castle for example) or when fitted into poorly insulated recessed lights.

It is easy to take external security lights for granted, particularly in the summer months, but these lights when situated close to the eaves can also set fire to the thatch just from the heat that they generate.

New health and safety regulations, even for small scale maintenance jobs, are driving thatchers to adopt safe working practices to work only off scaffolding. This might be good for the thatchers well being but can lead to an accumulation of debris on the scaffolding close to security lights, which on rare occasions have been blamed for starting a fire, with devastating consequences.

The National Society of Master Thatchers advises all its members and their customers to be aware of the risks associated with the high heat generated by halogen security lights. They advise thatchers to examine the location of these lights and to actively take steps to isolate security lights before any work is undertaken on the thatch. Isolating security lights should be part of the risk assessment carried out for each job as part of compliance with the HSE safe working practices and from the thatchers point of view to demonstrate due diligence for the rare occasions when things do go wrong.

As a general safety precaution halogen security lights should be situated at least one metre from any overhanging thatch or from a thatched porch.