The new EU energy efficiency policy (Recast EPBD Directive 2010/31/EU) and the 20/20/20 rule both call for improved building insulation measures in order to meet the energy-saving challenges of today's world. The building sector is the largest energy consumer, greater than either transport or heavy industry.
The technique of insulating buildings and dwellings using standard white expandable polystyrene (EPS) is well established. In the past decade a new generation of EPS has emerged in the market place. This type of polymer, 'grey EPS,' contains special additives that reduce the overall thermal conductivity of the foam produced from it, giving it better insulating properties in comparison to standard white EPS foam.
EPS Silver Polymer, a superior thermal insulation material from INEOS NOVA, is one such new product for building and construction applications. This article will provide an insight into the processing, properties and commercial applications of this new polymer.
The new EU energy efficiency policy (Recast EPBD Directive 2010/31/EU) and the 20/20/20 rule both call for improved building insulation measures in order to meet the energy-saving challenges of today's world. The building sector is the largest energy consumer, greater than either transport or heavy industry.
The technique of insulating buildings and dwellings using standard white expandable polystyrene (EPS) is well established. In the past decade a new generation of EPS has emerged in the market place. This type of polymer, 'grey EPS,' contains special additives that reduce the overall thermal conductivity of the foam produced from it, giving it better insulating properties in comparison to standard white EPS foam.
EPS Silver Polymer, a superior thermal insulation material from INEOS NOVA, is one such new product for building and construction applications. This article will provide an insight into the processing, properties and commercial applications of this new polymer.
1. Introduction
Today's public debate no longer questions the future energy availability and its soaring costs but focuses on how to reduce and control energy demand in order to secure a sustainable future, given the changes observed in the world's climate and population growth. We are living in an energy-intensive world which uses 82% fossil fuel as the main source of energy supply (Figure 1).
The world's primary energy demand of 13,000Mtoe (million tonne equivalents of oil) in 2010 will increase to nearly 15,000Mtoe by 2020 (Figure 2), with Europe accounting for 15% of this demand. The energy demand in the EU was some 2000Mtoe in 2010 (Figure 2). EU member states use more energy in buildings (42%) than in any other sector, followed by transport (30%) and industry (28%).
2. Energy
2.1 Sustainability
We spend the majority of our lives in buildings, whether at home, at work or for recreation. Buildings offer the greatest potential for energy-efficiency improvements in order to off-set the burden of growing energy costs from things such as heating homes, electricity and lighting, as oil prices increase due to growing demand, limited reserves and insecure supply.
The higher the consumption of energy stemming from fossil fuels, the greater the greenhouse gas emissions. Climate change threatens to make the world less inhabitable in the immediate future. Consequently, there is a general awareness among both the users and authorities to limit or reduce the energy consumption as millions of tons of carbon and billions of Euros could be saved by taking simple measures such as the installation of good insulation of buildings. This will help to build a more sustainable world in terms of the 1987 United Nations' definition of sustainability of 'meeting the needs of the present generation without compromising the ability of future generations to meet their own requirements.'
Building insulation is now accepted as one of the most effective and economically sound measures that we can take on the demand side to reduce energy use.
The EU has therefore taken concrete measures towards improving the energy efficiency of Europe's buildings by revising its legislation, mandating action for new and existing buildings and reinforcing the role of energy-performance certificates.
2.2 Measures
In addition to the already existing Energy Performance in Buildings Directive (EPBD) 2002/91/EC, the EU has taken a firm stance to meet its ambitious energy saving and climate change objectives. The 20/20/20 policy has fixed the following goals to be met by the year 2020.
- Reducing energy use by 20% compared to current projected 2020 levels;
- Increasing use of renewables to 20% of energy production;
- Cutting greenhouse gases by 20% compared to 1990 levels.
Furthermore, the original EPBD has been recast (2010/31/EU). This states that,
- All new buildings should be nearly zero-energy buildings by 2020 and Member States are to set upintermediate targets for 2015;
- EU Member States must draw up national action plans to increasr the number of nearly zero energy buildings.
- By 2018 new public buildings are to be nearly zero-energy buildings and display Energy Performance certificates.
3. Insulation in buildings
3.1 Rationale
The Building sector is the largest energy consumer but its consumption can be largely cut back through improving efficiency. Studies show that more than 20% of the present energy consumption (ie: 30-45Mt of CO2/yr) could be saved by applying new standards to new and when refurbishing existing buildings.
Heat losses (Figure 4) from a poorly insulated building can occur through walls (35%), roofs (25%), floors (15%) and from draughts (15%) and windows (10%). The energy loss per dwelling is dependant on the climate zone and the quality and quantity of insulation used. The insulation quality of buildings across the EU Member States is very variable.
3.2 Materials
The common materials used for insulation are foams based on polyurethane, phenolic or polystyrene (expansion or extrusion process) and mineral wool/fibre board. The thermal conductivity (also called lambda or referred to as the k-value) expressed in W/mK (or for convenience in mW/mK) is a measure of heat flow through a material at a given mean temperature. It is also related to the foam density and thickness. The lower the lambda value, the less conductive (or more insulating) is the material.
In the building and construction industry, the R-value is used, which is a measure of thermal resistance (foam thickness/lambda expressed in m2K/W. At times, the U-value (the thermal transmission coefficient expressed in W/m2K), is also used. It is the reciprocal of the R-value.
Owing to its good strength-to-weight ratio in combination with its constant insulation properties over the life time of a building, EPS foam has found a wide range of applications in building and construction (Figure 5).
Expandable polystyrene (EPS) beads can be expanded to produce EPS rigid foams of varying densities to suit different applications. The white EPS foam (standard) has enjoyed its status as a versatile insulation material in buildings since its invention in 1949. At present, INEOS NOVA has the best lambda white flame retardant EPS grade for building and construction applications.
In order to further improve the energy efficiency of buildings, a new generation of EPS polymers, so-called 'grey EPS' materials with lower thermal conductivities in comparison to the standard white EPS, have emerged in the market place during the last decade. The grey EPS market is expected to take up more than 25% of the construction market by 2013. INEOS NOVA has developed and commercialised EPS Silver Polymer (a trade mark of INEOS NOVA International S.A.) to respond to this insulation efficiency demand.
3.3 EPS Silver Polymer
EPS Silver is a specially designed polymer containing carbon-black additive, which gives the foam a unique black colour and enhanced thermal insulation properties. It is flame retardant allowing compliance with the DIN B1, Euroclass E and the French fire requirements for the ITEX (Isolation thermique par l'exterieur) application. It can be processed on existing EPS machinery.
The resulting foam has good mechanical and water absorption properties comparable to the standard. INEOS NOVA offers three grade types (S400LR, S400R and S500R) of varying bead size ranges to cover all the applications in building and construction.
3.3.1 Thermal conductivity of EPS Silver
The heat transfer in foam occurs via conduction, convection and radiation. EPS foam is made of 98%wt air and 2%wt polystyrene. Its small cell size of 50-200µm (Figure 6) precludes any heat transfer by convection.
Reducing the conduction component (due to gas and solid) would be difficult as EPS foam already contains air and the solid polymer accounts only for a very small part of this conduction. Hence, the option left to lower the thermal conductivity is to reduce the heat transfer due to radiation (Figure 7). INEOS NOVA has achieved this by addition of carbon-black in the polymer which acts a heat absorber (Figure 8).
As a result of the incorporation of this special infra- red absorber/reflector into EPS Silver Polymer, the contribution of the heat radiation to the overall thermal conductivity has been largely eliminated, particularly at low densities.
Figure 9 shows that at a foam density of 15kg/m3 EPS Silver has a thermal conductivity of 0.032W/mK. To achieve the same thermal conductivity with conventional EPS, a foam density of over 30kg/m3 would be required. At the same density of 15kg/m3, EPS Silver has a thermal conductivity of about 20% better compared to standard EPS. Consequently, an EPS Silver insulation board at this density with the same thermal resistance value would be 20% thinner compared to a standard EPS insulation board (Figure 10).
3.3.2 Processing of EPS Silver
EPS Silver Polymer can be processed on existing EPS machinery. The minimum achievable density of prefoam obtained in a single pass can vary from 16-17kg/m3 depending on the grade type, equipment and expansion conditions used. After maturing for two to three hours, these pre-foam beads can be second passed to 10-12kg/m3. The stabilised prefoam beads can then be further shape or block moulded to the desired dimensions depending on the application.
3.3.3 Foam properties of EPS Silver
The foams produced from EPS Silver Polymer yield good mechanical and water absorption properties. The 10% compression (load-bearing), bending (foam handling criteria) and cohesion (tensile) properties according to the CEN test methods are depicted in figures below. From the laboratory evaluation data, it can be concluded that EPS Silver, similar to the white standard EPS, fulfils the EPS Class 70 requirement at 15kg/m3 foam density (Figure 11).
Associated to this EPS Class 70, the requirements for the bending (Figure 12) and the cohesion properties (Figure 13) are also largely met. The EPS Class 100 requirement, commonly used in construction application, is also fulfilled with EPS Silver Polymer using a foam density of 20kg/m3 as is the case with the standard EPS material.
EPS Silver foams show very little water uptake even under total immersion conditions after 28 days according to EN 12087 (Figure 14). These values are comparable to standard EPS foams obtained under laboratory conditions.
4. Applications
The combination of improved insulation efficiency (20% better than conventional EPS foam) and good foam mechanical properties makes EPS Silver Polymer the insulating material of choice for building and
construction applications. The EPS Silver foam is being used to insulate various parts of buildings as illustrated in these images. Standard applications include use in external and internal walls, roofs, floors and between rafters. EPS Silver foam is also used to produce systems which can be used as finished elements for insulation purposes (e.g. external thermal insulation composite system (ETICS), insulated concrete form (ICF), lightweight concrete, finished roof elements, etc). There are also special applications such as thermo-acoustic and loose-fill cavity wall, which use EPS Silver Polymer.
4.1 Thermoacoustic
Low density EPS Silver foam block (10-12kg/m3) is compressed (Figure 15) under strictly controlled conditions (temperature, load and rate, thickness, time, etc...) in order to crush the foam cellular structure rendering it softer and more flexible.
The resultant material is a better absorber of incidental sound waves, thereby attenuating the impact of both contact and air-borne sound. As a result, EPS Silver foam possesses good acoustic and good insulating properties as it contains the heat absorber additive. This is a growing application in France known by the name dB-32.
4.2 Loose-fill cavity wall
This technique used to insulate hollow cavity walls is injection of an insulating material such as EPS prefoam beads alone (Germany) or together with bonding glue (UK, Republic of Ireland, Belgium and the Netherlands). The prefoam density used is 12-18kg/m3 depending on the country. The bonding agent used is an aqueous dispersion of organic polymer.
Some companies offer the entire package, ranging from expanded beads to the wall cavity filling. Other companies provide the pre-foamed beads to the franchised installers. Although insulation materials such as mineral wool or polyurethane resins with in situ foaming can also be used for this application, the use of EPS pre-foam beads offers an easy and cost-effective solution to retrofit old buildings as well as insulate new buildings. EPS Silver Polymer, a much improved insulating material is a product for loose-fill cavity wall application (Figure 16).
As the thickness of the cavity wall is fixed, higher R-values can be obtained by using EPS Silver in place of standard white EPS prefoam beads (Table 1). Installers in the UK and Ireland are already using this material, which enables regulations to be met whilst saving energy costs on heating fuel.
| Construction type |
Buidings |
Cavity mm |
U-value, W/m2 k |
|
| Non insulated | Insulated | |||
| Brick/cavity/brick |
70 | 1.68 | 0.39 | |
| Brick/cavity/Concrete black | Existing | 1.55 | 0.37 | |
| Brick/cavity/Clinker block | 1.40 | 0.35 | ||
| Brick/cavity/insulation block | ||||
| Brick/cavity/medium block & plaster | 100 |
0.27 | ||
| 110 | 0.26 | |||
| New | 120 | 0.24 | ||
| Brick/cavity/light block & Dabs | 100 | 0.26 | ||
| 110 | 0.25 | |||
| 120 | 0.23 | |||
Table 1: U-values for various constructions using EPS Silver.
5. Conclusions
Meeting the demands of our daily lives is getting costlier and more environmentally concerning due to the effect of global warming from CO2 emissions associated with the use of fossil energy. World energy consumption is rising to meet the demands of the growing world's population and increasing development, particularly in emerging economies. Both consumers and government authorities are becoming more aware of global sustainability issues due to this soaring demand and high price associated with the fossil energy.
EU legislative drivers in Europe such as the Recast Energy Performance in Buildings Directive and the 20-20-20 EU policies, mandate Member States to improve the energy efficiency of buildings, which are by far the largest consumer of energy compared to Transport and Industry sectors. Data shows that substantial reduction in CO2 emission and expense from fuel bills could be saved by taking measures to insulate the walls and roofs of the EU building stock, potentially resulting in greater than a 20% reduction in the energy use across the EU.
INEOS NOVA offers EPS Silver Polymer, an energy-efficient insulation, which is 20% more insulating than white EPS at similar foam density for building and construction applications. It can be processed using existing EPS machinery and allows superior insulation not only of new construction but also of renovated existing buildings, the latter forming 80% of the EU building stock prior to 1994. The high R-value constructions with EPS Silver foam will allow for considerable saving in terms of energy and heating oil requirements, enabling the EU to meet its ambitious energetic and environmental challenges of 2020 and contributing to the sustainability of our planet.
References
1. Nederlands Centrum voor Technische Isolatie, Seminar, 15 September, 2006.
2. EPBD Directive (www.epbd.nl)
3. World energy Technology outlook 2050 (ftp.cordis.europa.eu/pub/fp7/energy/)
4. Prediction of energy consumption world-wide (http://timeforcahnge.org)
5. EPBD Directive (www.epbd.nl)
6. EPBD recast (www.buildup.eu/news/9008)
7. The European portal for energy efficiency in buildings (www.buildup.eu).
9. Energy performance certificate (http://en.wikipedia.org/wiki/Energy_Perform ance_Certificate).
10. EPBD Buildings Platform: P05, 2006.
11. Review of the sustainability of existing buildings (www.communities.gov.uk)
12. Long, S. "Expanding into a sustainable future", Lecture, Global Insulation Conference, 2009.
13. Energy saving trust (www.est.org.uk)
15. www.dgi.org.uk
16. www.kemisol.be
17. E. Speroni, "Thermal conductivity of rigid polyurethane foams," 1983.
18. Kuhn, J. et. al., Int. J. Heat Mass transfer, Vol. 35. No.7, pp 1795-1801. 1992.
19. Coquard, R. et. al., "Modelling of heat transfer in low-density EPS foams,' Journal of heat transfer, Vol. 129, pp 538-549, 2006.
20. Rauniyar, G. "EPS loose-fill cavity wall insulation," Lecture, Global Insulation Conference, 2007.
21. EPS Silver Polymer is a trade mark of INEOS NOVA International S.A.
