Building control officers, architects, and builders – or indeed all those involved in the energy efficiency of buildings – will undoubtedly be exploring the most effective means of meeting the constantly increasing thermal insulation demands set out under Government legislation to meet the UK’s carbon saving commitments.
This includes a radical tightening of Part L Building Regulations. These are to be revised in 2010 and 2013, and again in 2016, as the Government moves towards zero carbon new homes.
In the meantime, the focus for further reduction in emissions will need to bed the retrofitting of the existing housing stock. This is especially relevant at a time when the economic situation has led to a substantial decline in the new build house market. Indeed, research shows that 2009 will beat the lowest peacetime housing figure since 1920. Housing starts in 2004 were at 213,000 and in 2009 are estimated to be 60,000. This highlights the need to update properties in the UK to meet its emissions targets.
For both new build and renovation/regeneration, it is anticipated that polyurethane foam will be in demand as well as proven method of meeting current and future thermal insulation requirements.
Spray applied or injected polyurethane foam is chemically-modified polyurethane foam, which can be applied to roofs, walls and ground floors to meet and surpass the insulation requirements of Building Regulations. It is also able to achieve U-Values and air permeability to meet the energy performance requirements of the Code for Sustainable Homes Level 3 – 25% less CO2; level 4-44% Less CO2 and Level 5/6 – zero carbon.
Polyurethane foam achieves a maximum U-Values depth of insulation and completely seals against unwanted air leakages. On-site sprayed or injected polyurethane foam seeks and seals all gaps. Therefore no costly corrections for air gaps are necessary in the calculations. Time frame and masonry cavity wall constructions insulated with polyurethane foam applied to the roof and walls have achieved air permeability results of 3m³/hr.m²) @ 50Pa. A typical timber frame wall would have required 50mm of polyurethane foam under 2002 rules to meet with 0.34W/m²K. Now an increase in thickness to 75mm will achieve 20% reduction, giving an acceptable U-value of 0.27/m²K. The current requirement is for new buildings to perform to a CO2 Target Emissions Rate that is 20% less than 2002 values.
Spray applied polyurethane foam applied to walls saves space. There is no need to increase cavity width to 5 inches to accommodate the depth of insulation (i.e. as for injected cavity insulation batts) to meet Part L Polyurethane foam can achieve 0.27W/m²K with a three inch cavity – with no loss of internal floor space.
Polyurethane foam can be economically applied to the underside of traditional roofs, as well as those constructed from steel, asbestos and aluminium. Systems can be applied to various depths and have a K-.Value of 0.23W/mK. When sprayed to a depth of 105mm the U-Value of a typical roof with 100mm of fibreglass at ceiling level is reduced from 0.34W/m²K to 0.16Wm²K, bringing the building up to current (2006) Building Regulations requirements. This can save the equivalent of more than one tonne of CO2 per annum in reduced energy consumption.
To avoid re-roofing a house that is simply suffering from nail fatigue, and to obtain optimum insulation, an 85mm layer of polyurethane foam can be sprayed on to the underside of the slates or tiles on a pitched roof. This stabilises and weatherproofs the roof by fixing nails, battens and roofing felt. As the foam is a superior insulant, coupled with just 50mm of insulation at joist level, the roof will also meet new build regulations. A typical roof can be insulated using the polyurethane treatment for around half the cost of re-roofing. By installing the insulation at rafter level it keeps the loft void warmer and prevents condensation build up which otherwise occurs when increasing insulation at ceiling level. The warmer, drier, cleaner roof space eliminates the risk of pipes and tanks freezing.
If more than 25% of the exciting roof is being repaired the roofing contractor now has a legal obligation to advise the clients to notify the local authority Building Control Department to comply with the new Part L Building Regulations. Generally the whole roof will need to be brought up to current thermal efficiency as required under Building Regulations. Thus using modern polyurethane technology, to save the existing roof, avoids incurring the much higher cost of completely re-roofing the property.
Spray-applied foam can be applied directly onto concrete to a depth of 60mm to achieve 0.22W/m²K and the conventional 75mm screed applied on top. For single story buildings, where the ground floor represents a high proportion of the space, extra insulation values can be achieved.
What are the benefits of Specifying the Process
High thermal polyurethane insulation systems can be spray applied to the required insulation value. Applied as a liquid to roofs, wall and ground floors, it expands to create a superior insulation and acoustic barrier. The two component liquid system produces a highly-efficient blanket of insulation with the thermal conductivity of 0.023W/mK. It is particularly easy and effective to apply a wide variety of substrates and is fibre free. Its closed cell nature renders it very resistant to moisture ingress and grades are available which achieve both Class 1 and Class 0 fire rating when tested to BS476 Part 7 and Part 6 respectively. Furthermore, it has a very good track record in retrofit applications, both domestic and industrial/commercial.
One of the most important aspects of spray-applied polyurethane foam is the fact that it produces a seamless blanket of insulation giving rise to product without joints. Any jointed system, including insulation boards, gives rise to a potentially weak point leading to a significant loss of insulation value. In a report carried out into the life cycle assessment of insulation materials, it was concluded the PUR foam can make an important contribution to the protection of the environment, especially through retrofitting of existing buildings.