Technical Overview
Failure to stop the flow of air through the home, office or factory envelope means that new air is constantly infiltrating the space and will require re-heating. Research conducted in America indicates that as much as 40% of the energy wasted in each home is caused by air infiltration, but by ensuring you minimise areas where air can enter will help to keep your energy costs down as the air won't need re-heating as often.
Permaseal's spray foam roof insulation can help you achieve this by upgrading the thermal performance of your roof. Principally used as a stabilisation medium on pitched roofs, it forms a seamless weatherproof barrier stopping wind, driven rain, snow and dust. It contains no nutritive value and will prevent access to vermin and birds. Humidity, moisture and condensation have virtually no effect on the sprayed polyurethane foam, which results in a cooler environment in summer and a warmer environment in winter.
Technical Specifications
The Duratherm polyurethane spray is a 2 compound system comprising of isocyanate and resin in equal amounts. It is an open celled, spray applied semi-rigid polyurethane foam system. Sprayed polyurethane foam cures within seconds of being sprayed and forms rigid foam. It is suitable for both internal and external roof applications and meets Part L of the Building Regulation Standards.
The spray foam is HCFC and CFC free, has zero ozone depletion potential and has been tested in accordance with BS 476: Part 7: 1997 in relation to the spread of fire and has been categorised as Class 1.
The application has a service temperature range of -15°C to 70°C.
The Pirthane system is unique in passive fire protection and is widely used in industrial and commercial soffit insulation. It is the only system to offer air tight, on-site formed, spray foam insulation. Pirthane is usually installed on the ceilings of underground car parks, with fast track installation and no mechanical fixings, making it swift and convenient to install.
It has a Class '0' surface spread of flame so is entirely suitable for interior applications, and is the only spray foam application which can be coated with a compatible intumescent (fire retardant) coating. The foam, along with the coating, can result in exceptional thermal properties and stringent U-Values. It offers outstanding permanent adhesion to any surface, ensuing seamless insulation and effective condensation control.
Typical U values
"U" Factor indicates the level of “U” Loss, which is essentially how much heat is escaping from the materials. A smaller “U” Value means a reduced amount of heat loss, and so usually the thicker the material the better. As such the usual depth of the materials used to encase roofing materials in a domestic setting is:
- 20mm offers a "U" Value of 0.98
- 40mm offers a "U" Value of 0.52
- 50mm offers a "U" Value of 0.45
- 75mm offers a "U" Value of 0.29
- 100mm offers a "U" Value of 0.20 (advised in new buildings)
- 150mm offers a "U" Value = 0.15
When applied, the foam coats the materials up to 2 inches from the eaves of the roof, ensuring that there is adequate air-flow right the way through the roof area, but that the “U” Value isn’t effected.
- Polystyrene 64mm ( 60%)
- Mineral Fibre 72mm ( 80%)
- Cork 80mm (100%)
- Cellular Glass 88mm (120%)
If the depth of the normal foam is 40mm you would need to combine other materials such as polyester, mineral fibre, cork and cellular glass, to increase the “U” Factor and give the desired level of insulation. However there would be no adhesion or increase to the stability of the roof and it would be much more complicated and take longer to install.
Compare this with an application of domestic spray foam which is normally finished on the same day and will cause the least amount of disruption possible and a number of distinct advantages.
Moisture in Roof Timbers
Concerns and reservations about the product are often centred on the potential problems of water retention on the load bearing roof rafters that are partly encapsulated. These concerns are completely unfounded and have no scientific basis. On an average roof rafter measuring 100m x 75mm, 35% of the surface area is left exposed. This, coupled with the fact that the polyurethane spray foam has the same ability to breathe as timber, results in no greater amount of moisture being transferred into the timbers once the installation has taken place.
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