External Roof Insulation with Naturheld Wood Fibre

Externally insulating a roof with wood fibre sarking boards is very effective because the complete roof structure is covered in insulation, so cold bridges through the rafters are avoided. This type of roof is called a warm roof. This heat retention is very considerable because the rafters typically take up 9 to 15% of the entire roof surface, and the heat will escape through these timber elements. Warm roofs are installed when the attic area is being used as living space or where the property has vaulted ceilings.  It is more economical to insulate the attic floor if the attic space is not being used.

Because Naturheld 220/180/140/110 boards are water-resistant, they can be left exposed on pitched roofs for up to 4 weeks if all non-T&G junctions, such as at the ridge, valleys or penetrations, are primed and taped.  Alternatively, the Naturheld 220/180/140/110 boards can be covered with the Ampatop Protecta Plus or Ampatop Seal Breather Membranes without the need to tape those joints.  We strongly recommend using a membrane because the internal building structure will remain dry to allow construction work to proceed. The membrane can be left exposed for 3 months. The tongue and groove joints on Naturheld 220/180/140 boards reduce rain and thermal leakage.  Wood fibre sarking boards will also keep the roof timbers warm and dry throughout the life of the building, so will reduce any risk of rot or damage.    

Naturheld wood fibre insulation boards are a totally natural and renewable product, as well as being vapour-open, hygroscopic and capillary-active.  This means that condensation and vapour within the property can pass through the wood fibre insulation and evaporate away from the ventilated cavity above the insulation. Moisture won’t become trapped, so this keeps the building fabric much drier, and therefore, healthier and warmer. This greatly reduces the chances of mould, wet rot or dry rot occurring.

Sound insulation through the roof will be greatly enhanced with the addition of dense wood fibre sarking boards so noise from rain, traffic or airplanes should be significantly reduced.

Loft areas of buildings tend to overheat during the summer because there is virtually no thermal mass in a roof covering. With the addition of wood fibre boards, this excess solar gain heat from the sun will be stored for between 10 and 12 hours, when it will then be released as temperatures drop, whereas other insulation materials can only provide 5 to 8 hours lag time. This keeps buildings a few degrees cooler during the warmer summer months. The reverse happens in winter when the heat from the central heating system will be stored in the wood fibre layer and released at night-time as temperatures drop. This is particularly crucial when the loft space is used as living accommodation.