New technical solutions for energy efficient buildings

State of the Art Report

Sustainable building materials

Heimo Staller, Angelika Tisch

IFZ

July 2011

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Background

Over their life cycle building materials have various impacts on mankind and the environment. Building materials influence the health of the workers during the extraction of resources and the construction proc-ess as well as the health of the users of the building. They also influence the environment directly (e.g. use/depletion of resources and energy, impacts by emissions). Figure 1 shows some of the most impor-tant emission aspects that should be considered during an assessment of building materials.

Fig. 1 Building materials and environment, 1= health aspects in the construction process, 2= health aspects concerning indoor air quality in the use stage, 3= environmental aspects within the life cycle: emissions to ground, water, air, flora and fauna [2].

Among the direct influences of building materials on the environment are the following:

• The ecological footprint of some of the building materials is considerable, for example:

o the energy used to mill or to bake the products. From a life cycle perspective, the en-ergy used during the operation of a conventional building is generally higher than the energy used during the production of building materials. But nevertheless as the energy demand of buildings decreases (towards nearly zero energy buildings in 2020 as stated in the recast European Directive on energy performance of buildings[1]), the energy demand for the production of building materials becomes more and more important.

o the amount of non-renewable resources used. This is apparent not only at the sites of open-pit mining but also in the fact that around 50 % of all waste produced in the EU comes from the building and construction industry. Many of the resources currently used are non-renewable resources such as stone.

• As we spend around 90 % of our time in buildings, the indoor climate and the quality of the

air influence our well-being. However the procurement of low-emission building materials is rarely a priority in public procurement. In addition to the well-being of the residents of the building, the well-being of the workers who produce or handle the building products should also be considered.

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What are sustainable building materials?

To answer this question, a sustainability assessment of building materials should be done on the whole building level over all life stages (when a whole building is being procured), taking into account aspects such as the energy demand in the operation stage (see figure 2). For example, even if concrete has a high environmental impact (e. g. embodied energy) during its production, the use of concrete might be justified because it increases the thermal mass of the building and therefore reduces the heating and cooling en-ergy demand during the use stage.

To handle the complex topic of sustainability CEN1 TC 350 [3] provides a system for the sustainability assessment of buildings using a life cycle approach and quantitative indicators for the environmental per-formance, social performance and economic performance of buildings. In CEN TC 350 "Sustainability of construction works – Sustainability assessment of buildings" sustainability in the building sector is divided in three ways:

• Ecological sustainability

• Economical sustainability

• Social sustainability

The life cycle is divided into the "Product stage", the "Constructions Process stage", the "Use stage" and the "End of life stage" as can be seen in the next picture.

Fig. 2 Life cycle stages of buildings defined in CEN TC 350 [3]

1 CEN is the European Committee for Standardization

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Not to go beyond the scope of this document, this report focuses only on selected ecological sustainability aspects and indoor air quality (which in CEN TC 350 is allocated to social sustainability) of building mate-rials.

How to assess the ecological sustainability

In CEN TC 350 the following environmental indicators are recommended to be used to describe the envi-ronmental performance of buildings and building materials over their life cycle:

1) Indicators for environmental impacts expressed with the impact categories of LCIA (life cycle impact assessment)

• climate change (e.g. in kg CO2- equivalents)

• destruction of the stratospheric ozone layer

• acidification of land and water resources (e.g. acidification potential in kg SO2- equivalents)

• eutrophication

• formation of ground-level ozone

2) Indicators for environmental aspects expressed with data derived from LCI (life cycle inventory) and not assigned to the impact categories of LCIA

• use/depletion of non-renewable resources other than primary energy

• use of renewable resources other than primary energy

• use of non-renewable primary energy (e. g. in MJ/m2 construction area)

• use of renewable primary energy (e. g. in MJ/m2 construction area)

• use of freshwater resources

• non-hazardous waste to disposal

• nuclear waste to disposal

• hazardous waste other than nuclear waste to disposal

• construction demolition waste for material recycling

• construction demolition waste for energy recovery

Even if the sustainability assessment of building materials should be done on the whole building level over all life stages, sometimes – for example during a renovation project where only insulation material is pro-cured – there is no other way than to assess building materials on the level of building components or buil-ding elements. Not to go beyond the scope of this report, below the use of two environmental indicators

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"primary energy demand" and "CO2- equivalents", which are considered to be f the most important indica-tors in the building sector, is exemplified. Procurers who ask suppliers for the primary energy demand and the CO2-equivalents of their building materials should ensure that they have a good understanding of this topic or involve experts in the procurement process. One way of verifying whether bids fulfil the required environmental specifications is to ask for Environmental Product Declarations (ISO 14025, type III). They provide information about the environmental performance of the product, for example the CO2-emissions in the product stage. As Environmental Product Declarations are voluntarily developed and exist at the moment only for some building materials like insulation material, information concerning generic, environ-mental specifications of building materials can be found in databases like ECOINVENT 2.

Primary energy demand in procurement

Primary energy demand (often also called embodied energy) is an indicator for the use of primary energy along all life stages of the building material (not of the building itself), and can be used by procurers to compare different products to be used in construction.

In order to use primary energy demand, a procurer would need to consider the following issues:

• Defining primary energy demand

For the ecological assessment the primary energy demand should be split up into primary energy demand

non-renewable and primary energy demand renewable3, whereby primary energy demand non-renewable is the more important indicator. In general it can be stated that building products based on non-renewable raw materials have a higher primary energy demand non-renewable than building products made of re-newable materials (e.g. an insulation product based on crude oil will have a higher demand than products based on wooden materials) , but nevertheless during the procurement process, specifications with quanti-fied benchmark values should be used for primary energy demand renewable too.

• Comparing like-for-like

For procurement an exact definition of the functional units and equivalents4 for the primary energy demand is required, otherwise the bids cannot be compared. 2 ECOINVENT is one of the most commonly used databases in Europe, provided by the Swiss Centre for Life Cycle Invento-ries, http://www.ecoinvent.ch/

3 Primary energy demand non-renewable means the amount of non-renewable primary energy consumed throughout the life cycle of the product (or the stage of this life cycle that is being assessed). Primary energy demand renewable means the amount of renewable primary energy consumed.

4 CEN TC 350 differs between functional equivalents and functional units. A functional equivalent is the basis for the as-sessment of whole buildings under pre-established building performance characteristics (e.g. a residential building with 50 flats with the passive house standard, fulfilling the Austrian building code, etc.). Functional equivalents are used to compare different design solutions for a whole building. A functional unit is used to compare building components and building prod-ucts fulfilling specific performance characteristics (e.g. 1 m2 of a timber wall with a u-value of 0.15 kWh/m2/a).

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. Functional equivalents/units that can be used in the procurement process include:

• Primary energy demand renewable/non renewable in GJ/building (= functional equivalent)

• Primary energy demand renewable/non renewable in GJ/m2 gross floor area (= functional unit)

• Primary energy demand renewable/non renewable in GJ/m2 construction area (= functional unit)

It is most effective to use the whole building/functional equivalent approach, as this enables the most comprehensive, realistic assessment of the different offers. This would mean asking potential bidders to submit the primary energy demand (renewable & non-renewable) for their whole proposal, and would allow this to be evaluated alongside other important aspects, particularly the primary energy demand of the whole building during its use. To get comparable bids, it is highly recommended to provide a calcula-tion method (programme) for the primary energy demand to be used by all bidders,

In table 1 an overview of the primary energy demand (GJ) and of the CO2- equivalents (for a definition of this indicator see chapter CO2- equivalents on the following pages) of different insulation materials is given (the system boundary for the LCA-data is cradle to gate5)

Insulation material PE non renewable

GJ-Eq/m2

PE renewable

GJ-Eq/m2

PE total

GJ-Eq/m2

to of CO2-

Eq/m2

Polystyrene 0,32 0,00 0,32 0,0109

Foam glass 0,26 0,14 0,41 0,0158

Cork 0,12 0,34 0,46 -0,0207

Mineral foam board 0,10 0,01 0,10 0,0095

Table 1 Overview of the primary energy demand in GJ (Gigajoule), renewable, non renewable and CO2- equivalents of dif-ferent insulation materials (1 m2 of insulation, u-value 0.30 W/m2K, thickness ca. 14 cm). Results are based on the IBO Database and calculated with the ECOSOFT LCA-programme (the system boundary for this LCA is the product stage, which explains the minus of CO2- equivalents concerning cork, the bonus is caused by CO2 stored in the building material) [4].

• Building lifespan

A definition of the building’s life span must also be given (e. g. 50 years) by the procurer, as the re-placement cycle of building components/elements influences the primary energy demand. If a building material lasts for only 25 years, then over a 50 year lifespan you will need to calculate the primary energy demand twice.

5 Cradle to gate contains only the product stage (raw material supply, transport, manufacturing of building

products). See also figure 2 “Life cycle stages of buildings defined in CEN TC 350” on page 2.

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• System boundary

To reduce the complexity in the procurement process it might be reasonable to restrict the part of the construction material life cycle which is assessed – i.e. to restrict the “system boundary”. Typically the product stage (excluding construction, use and end of life stage, (see figure 2 “Life cycle stages of build-ings defined in CEN TC 350” on page 2), typically covers for by far the largest share of the primary en-ergy demand in the average product life cycle. This may therefore be a usable system boundary for a procurer to define.

CO2-equivalents in procurement

CO2-equivalents are the most common indicator to express the impact on climate change (Global warming potential). The indicator CO2-equivalents is often used to describe the impact of energy consumption in the use stage of buildings on the environment. Many European countries use them as reference value in their energy certificates. CO2 – equivalents can also be used to express the environmental performance of building materials over their whole life cycle, and may be used by procurers besides primary energy de-mand.

Similar to the primary energy demand non renewable, building materials based on renewable raw materi-als (e.g. wood, straw, hemp) tend to have lower CO2-equivalents. In some cases they can be CO2 neutral (like sawn, untreated wood, with low transport distances to construction site). Strategies for the implemen-tation of CO2-equivalents are similar to primary energy demand. In table 1 CO2-equivalents for insulation materials are shown. As with primary energy demand the following functional equivalents/units may be used in the procurement process:

• CO2– equivalents in tons/building (= functional equivalent)

• CO2– equivalents in tons/m2 gross floor area (= functional unit)

• CO2– equivalents in tons/m2 construction area (= functional unit)

Indoor Air Quality

As most life cycle assessments do not cover the impact of building materials on human health and eco-toxicity, these impacts should be addressed in addition to the life cycle assessment. One of the most common ways to do so is to include tender criteria limiting or prohibiting at least the following substances:

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• Ingredients classified2 as dangerous for human health: carcinogenic, mutagenic, toxic for re-production or sensitising.

• Ingredients classified2 as dangerous for the environment.

• Other ingredients being probably dangerous for the human health or the environment and which are not classified or prohibited yet. For example toxic heavy metals, hydrofluorocarbon (HFCs), chlorinated hydrocarbons, phthalates or biocides.

• Volatile organic compounds (VOC), semi-volatile organic compounds (SVOC), aromatic hy-drocarbons and heavy metals.

Necessary Steps

To guarantee that building materials are free of these substances, the following steps have to be taken:

• The public procurer must include appropriate criteria in the tender documents (possible sources for criteria are offered below).

• The supplier must provide the procurer with a list of products that the company is going to use as building material on the construction site including proof that the criteria in the tender documents are met (proof may be offered by presenting the safety data sheet or the product data sheet).

• The procurer must verify if the products included in the suppliers’ list comply with the criteria in the tender. This is an important step that might not be easy for a procurer who lacks the chemical knowledge. But there are some tools available that can help the procurer with the verification (see below).

• The procurer must inform the supplier about those products on the list which are allowed and those which are forbidden. For forbidden products, the supplier has to find substitutes. The procurer can also offer a list of possible substitutes. The last two steps have to be repeated until all the products on the suppliers’ list are released by the procurer.

• The public authority must ensure that the supplier uses only those products on the construc-tion site which are on the list. Therefore a quality control system should be implemented. This system should include at least one or more meetings on site with the supplier and his staff where information about the quality control and the products released is given as well as the continuous supervision on the construction site.

2 Classified according to the CLP Regulation (Regulation on classification, labeling and packaging of substances and mix-tures) No 1272/2008.

2 Classified according to the CLP Regulation (Regulation on classification, labeling and packaging of substances and mix-tures) No 1272/2008.

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Possible sources for appropriate criteria

There are several sources for appropriate criteria (the term “green criteria” used below only refers to in-door-quality-criteria):

• European criteria for the procurement of building materials that offer a high indoor quality: The European Commission currently offers common green EU-criteria for the procurement of the following building materials: windows, glazed doors and skylights, thermal insulation, hard covering and wall panels. For more information please go to http://ec.europa.eu/environment/gpp/second_set_en.htm.

• Green criteria for the procurement of building materials developed by initiatives in the Member States: There are several initiatives in Europe that have developed green criteria for the pro-curement of building materials. One of them is ÖkoKauf Wien3 (only available in German) which offers green criteria for a larger number of building materials.

• Ecolabel-Criteria: the Ecolabel nature plus4 is designed especially for building materials. In addition there are other Ecolabels like the EU flower5, the Österreichisches Umweltzeichen6, the Blauer Engel7 or the Nordic Ecolabel8 that cover at least some building materials. You may go to the website of the Ecolabels and inform yourself about the building products for which criteria exist. You can then select some of the criteria that relate to the quality of the product. For example, the EU flower offers criteria for floor coverings and outdoor paint and varnishes.

Tools that can be used for the verification of products

For the verification of products, an electronic platform that identifies those products on the market that meet the indoor-quality-criteria is useful for the procurer. Even if the platform doesn’t include every building product available on the market, it facilitates the verification process if some of the building products are on the platform. A separate report on declaration platforms for building products in the European Union is currently being developed. Current platforms include:

• .

• The Austrian baubook9 - offer a wide range of buildings products that meet the criteria of ÖkoKauf Wien and of other Austrian authorities.

3 http://www.wien.gv.at/umweltschutz/oekokauf/ 4 http://www.natureplus.org 5 http://www.eco-label.com 6 http://www.umweltzeichen.at 7 http://www.blauer-engel.de/en/index.php 8 http://www.nordic-ecolabel.org/ 9 http://www.baubook.at/

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• The Swedish basta10 - offers building products without hazardous chemicals.

• Each of the Ecolabels mentioned above also offers information on its website about the build-ing products which are certified with the Ecolabel

Examples of innovative, sustainable building products

In the following chapter, a selection of innovative and sustainable solutions for commonly used building materials is presented.

SLAGSTAR – ECO CONCRETE

Although most components of concrete are based on natural materials like gravel, sand and water, normal concrete is characterised by high values of primary energy demand and CO2– equivalents. This is mainly caused by the use of cement (e. g. Portland cement), which is produced in a very energy intensive proc-ess. Some companies have developed an alternative to this energy consuming type of cement by the use of so called SLAGSTAR cement, which is mainly based on slag sand. With these measures reductions of up to 80 – 90% of CO2-equivalents are possible. By the use of 1 m3 of SLAGSTAR ECO CONCRETE savings of 0.18 tons of CO2- equivalents in comparison to normal concrete are feasible. SLAGSTAR ECO CONCRETE can be used for all types of concrete and all applications. http://www.oekobeton.at/front_content.php?idcat=362

Fig. 3 Primary energy demand and CO2– equivalents of concrete and cement over all life stages, based on calculations with the SimaPro v7.1.8 LCA software tool and on the Ecoinvent v2.0 database [5].

10 http://www.bastaonline.se/english

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RC – Recycled Concrete

Recycling of building materials can also decrease environmental impacts. For many technical applications recycled concrete (RC) is a sustainable alternative to conventional concrete, reducing the use of primary energy, raw materials, freshwater and land. Besides back filling of trenches and base frames of streets, which is already common practice in most European countries, RC can be used in building construction. In Switzerland the City of Zürich together with the enterprise Eberhard Bau AG has established a broad im-plementation of RC in building construction. The percentage of recycled concrete used in diverse con-struction projects is up to 90%.

Fig. 4 Application of RC: ETH e-science Lab, Zurich, Switzerland, 2008, Baumschlager Eberle, Lochau ZT GmbH [6].

http://www.urbanmining.ch/fragen.php

Innovative insulation materials – mineral foam boards

Most thermal insulation composite systems use EPS (expanded polystyrene) as an insulation material. EPS is mainly based on crude oil, which has a number of negative environmental impacts (high primary energy demand non renewable and high CO2-equivalents, recycling problems). In the last few years major companies of the insulation sector (such as STO, Xella International GmbH) have developed alternatives to EPS using a mineral base. Products such as StoThermCell or Xella Multipor are based on lime and cement, characterised by better environmental performance. Further more these products can be recycled easily (e. g. reuse as mineral back filling).

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Fig. 5 Ecological indicators for Xella Multipor mineral foam board compared to the benchmarks of the natureplus Label6. Light grey= Xella Mulipor, dark grey= benchmarks of natureplus [7].

Key: PEI n.e. = Primary energy demand non renewable, GWP = Global warming potential, POCP = Photochemical ozone creation potential, AP = Acidification potential

http://www.ytong.at/de/content/ytong_multipor_mineraldaemmplatten_1270.php

http://www.sto.at/evo/web/sto/32217_DE-Daemmsysteme-StoTherm_Cell_-_mineralisches_nichtbrennbares_WDV.htm

Timber products

Being a renewable and CO2-neutral material, timber offers a high potential for sustainable construction. For example 1 m3 of timber stores around 1 tonne of CO2. But for the procurement of timber products some requirements still have to be taken into account:

• Wooden raw products should be derived from legal7 and sustainably managed forests. To fa-cilitate this, in the technical specification of the tendering documents guarantees for these re-quirements should be asked for. Verification from the supplier that their timber meets these standards can be provided by certificates such as FSC- or the PEFC-label, although other

6 natureplus is the international label of quality for sustainable building and accommodation products, tested for health, envi-ronmental-friendliness and functionality. http://www.natureplus.org/

7 Much timber which appears on the European market derives from illegal logging operations

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equivalent forms of proof must also be accepted8.

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• Other environmental impacts (e.g. primary energy demand and CO2- equivalents) should also be part of the tender documents. In general it can be stated, that local, untreated, sawn timber offers the best environmental performance.

Fig. 6 Primary energy demand and CO2- equivalents over all life stages of different timber products, based on calculations with the SimaPro v7.1.8 LCA software tool and on the Ecoinvent v2.0 database [5].

Below some innovative timber products are presented:

Holz 100

Holz 100 is a massive timber construction system developed by the “Ing. Erwin THOMA Holz GmbH” company in Austria. It is a system for walls, slabs and roofs constructed with untreated pinewood boards. Unlike other timber construction systems Holz 100 consists of no glues and metals, but is joined instead by dowels made of beech wood.

Fig. 7 House constructed with Holz 100, Ing. Erwin THOMA Holz GmbH

http://www.thoma.at/html/deutsch/index1.html

8 The UK timber procurement policy offers a useful model for procurers to use: www.cpet.org.uk/uk-government-timber-procurement-policy

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Topwall-System

The Topwall-System has been developed by the Swiss engineer Hermann Blumer. It is based on pine-wood beams (10 /20 cm) and the whole construction system is made of wood (including the fasteners). Because of the small size of the basic element the construction can be handled without a crane by one person.

Fig. 8 Topwall-System, Construction project Badenerstrasse 380, Zürich, Switzerland

Venster – Wooden Passive House window

The Passive House window “Venster” has been developed by the company Sigg in Hörbranz, Austria. Unlike other qualified passive house windows, whose frames and sashes are made of different compo-nents (wood, insulation foam, e.g.), this window is a pure wooden construction.

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Fig. 9 Venster – Wooden Passive House window, company Sigg, Hörbranz, Austria

http://passivhausfenster.at/general/the-2018venster2019

References [1] Directive 2010/31/EU of the European Parliament and of the Council of 19 May 2010 on the energy performance of build-ings

[2] Staller, Heimo; 2011

[3] CEN TC 350 Sustainability of construction works – Sustainability assessment of buildings sustainability, 2008

[4] Staller, Heimo; 2011

[5] Ignacio Zabalza Bribián, Antonio Valero Capilla, Alfonso Aranda Usón: “Life cycle assessment of building materials: Comparative analysis of energy and environmental impacts and evaluation of the eco-efficiency improvement potential, Building and Environment”, volume 46, issue 5, 2011

[6] Baumschlager Eberle, Lochau ZT GmbH, ETH e-science Lab, Zurich, Switzerland, 2008

[7] Ecological indicators for Xella Multipor mineral foam, IBO magazine 2/09, Vienna, 2009