Metal roof insulation and metal wall cladding insulation, an effective solution
Metal is known to be one of the best thermal conductors there is, hence the reason your pans are made from stainless steel. Conventional radiators are also made from steel, as they are designed to allow the heat source to radiate through the surface as quickly as possible.
Unfortunately, this is also true for metal clad industrial and farm buildings, which suffer from both heat loss and condensation. The issues are almost always more noticeable in the winter months, when the internal temperature is warmer than the ambient, resulting in water vapour from inside the building coming into contact with the cold metal cladding and then condensating. The buildings can also become incredibly hot in summer as the suns heat can quickly pass through the metal.
Conventional insulation products, such as mineral fibre batts or insulation boards, whilst adding a reasonable amount of insulation, have proved to be largely unsuccessful in preventing condensation. This is because of the way the batts / boards are installed, being placed edge to edge so that they do not form a continuous barrier, therefore allowing thermal leakage and air to move behind the insulation.
This air, when carrying water vapour, will quickly condensate beneath the metal cladding. Once enough condensation has developed, it will drip down onto the insulation and then find its way through joins. Alternatively it may start to permanently saturate and damage the insulation, particularly if mineral fibre batts have been used. This problem has been solved by allowing up to a 150mm air gap between the cladding and the insulation to allow sufficient air flow, though this contributes to further heat loss rendering the insulation almost useless!
Is there a better Metal roof insulation solution?
Thankfully yes. A ‘closed cell’ polyurethane foam when spray applied forms a continuous, ‘hermetic’ seal (http://en.wikipedia.org/wiki/Hermetic_seal) providing superb Metal roof insulation. The foam is applied directly to the underside of the metal cladding, eliminating any air gaps and preventing the formation of condensation. A thickness of 25mm will prevent condensation, though the u-value of the insulation is governed by the thickness and a greater thickness than 25mm may be required depending on the specific use of the building.
So in one application, we have solved both the problem of condensation and Metal roof insulation using polyurethane spray foam.