In simple terms, rigid foam is a mixture of five different chemicals, including a fire retardent which when combined, form a multi use rigid foam that when applied expands to over 30 times its original volume. When processed through suitable spray machinery it will produce a rigid foam of approximate density 34lb/m2 with exceptionally good comprehensive strength. Since the 1970s, spray foam has been used to insulate many thousands of domestic and commercial buildings.
In 1849, a chemist named Charles Werts began experimenting with mixing chemicals with the aim of producing foam. Although encountering many problems along the way, by 1960 scientists had finally developed a good quality substance that with a little more work, could be applied using a spray gun.
How does the cost or Rigid Foam compare with re-roofing?
Extremely well! Generally, treating a roof with spray foam will cost just half as much as re-roofing depending on the size and condition of the roof. Why not contact us for a FREE survey and estimate to find out.
Absolutely! Applying rigid foam to the underside of your roof provides a significant reduction in heat loss (often up to 30%) Consequently, heating costs are dramatically reduced. Find out more on the benefits of rigid foam.
Can it cause condensation or rot timbers?
No, rigid foam actually prevents condensation and because it is not a vapour barrier allows timber to breathe. Technically foam breathes at the rate of 60 grams of moisture, per m2 per day.
Problems associated with the decay of timber in buildings are usually blown out of proportion because of a naturally occurring process. If timber components are kept dry i.e. there is no abnormal ingress of water into the roof space either in the form of rainwater or excess humidity, then they will be stable for long periods of time. However, excess moisture can allow the colonisation of timber by wood decay fungi, notably organisms causing wet and dry rot.
A roof undersealed with sprayed foam, which in itself is closed cell and waterproof, will help to keep the timber battens dry for two reasons:
1. The water vapour resistance of p.u is sufficient to prevent interstitial condensation but is permeable enough to allow the battens, which are covered on the 3 sides by the foam to 'breath'. In addition, by preventing wind blown rain and snow, the battens stay dry.
2. Insulation at roof level keeps the temperature in the loft higher, preventing condensation build-up which otherwise occurs when increasing insulation at ceiling level. Thereby again, helping to keep battens dry.
The core of any wood rot control strategy is therefore, remove any source of moisture. Consequently on a house roof, the usual forms of roof maintenance to lead work, pointing etc will provide the primary source of waterproofing and the foam will do the rest.
Does Spray Foam Insulation present a fire risk?
Polyurethane foam meets BS 476 part 7: 1997 to a a class 1 surface spread of flame rating.
What about noise reduction. Does spray foam offer acoustic insulation?
Yes, in fact some of our work involves acoustic insulation on new build properties of multiple occupancy like flats and apartments.
What is a U-value and how does it affect my installation?
The U-value is a measure of the heat flow through the walls or roof of a building. The higher the U-value the more heat flows through so the lower the value the better insulated your building will be.
To calculate a composite 'U' value much additional information is required. However, for thin skin structures like asbestos, steel or aluminum the effect of the substrate can be ignored, and the composite 'U' value taken as that of the foam, knowing that the composite will be better.
| Foam Thickness | K Factor (W/M2 oC) | U Value (W/M2 oC) |
| 25mm | 0.023 | 0.877 |
| 30mm | 0.023 | 0.689 |
| 35mm | 0.023 | 0.600 |
| 40mm | 0.023 | 0.529 |
| 50mm | 0.023 | 0.431 |
| 75mm | 0.023 | 0.293 |
Please Note: The proposed insulation standard for industrial buildings requires a 'U' value of 0.60 W /M2 oC. This figure includes the factor for surface to surface resistance.
Yes, we offer a 15 year guarantee for materials and work carried out at your property. Feel free to Contact Us for more details.
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Roof Rescue
Trent, North Petherwin, Launceston, Cornwall PL15 8GW
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