Validity and comparability of assessment results, functional equivalency

Transcription

1 Validity and comparability of assessment results, functional equivalency Sylviane Nibel CSTB, Boris Bosdevigie CSTB, Abstract A set of core indicators is essential for the development of sustainability schemes in order to assess building toward overall subjects of concern related to environment, society and economy. The reliability of sustainability assessment lies on the validity of developed indicators and on the comparability of assessment results. SuPerBuildings projects has developed recommendations to insure the relevance of indicator to measure the performance of buildings. The main findings put in evidence the necessity to establish a clear link between indicators and issue of concern, but also to give transparency to method used to calculate and epress indicator. The step following the development of valid and comparable assessment method is to propose a coherent framework to benchmark buildings through a multicriteria approach. Comparing buildings and rating its involve to consider multiple parameters as project characteristics (i.e. use oriented typologies, provided functionalities) or specificities related to the surrounding environment (i.e. eternal constraints related to location, urban contet, local requirements and law, etc.). Taking into account this kind of parameters may end up adjusting accordingly the target of the benchmark. The scale of performance will be thereby defined in relation to a functional. Adjusting the performance scale of a benchmark is not always feasible. In order to prevent bias or opposite effect, other potentially influencing parameters should be reported to understand the specificities of a project as constraints related to location or provided functionality.

2 Assessment method of indicators functional Selection of indicator considering relevancy and validity toward object of concerns Rules for calculation of indicators that enable precision and reproductibility of results. Rules for normalization and aggregation. List of parameters describing the object addressed by the benchmark Other information considered as relevant for the comparison (e.g. indicator of local constraints, declared functional..) Contet and purpose of the benchmark: - Objectives of sustainability; - Political, and economical contet; - Interested groups and stakeholders; benchmark values From a bottom-up approach (e.g. statistical eperimentation, calculated values, technical or economical optimum...) From a top-down approach (e.g. needed target to make significant improvement, political target, etc.)

3 Validity of indicators VALIDITY AND COMPARABILITY OF ASSESSMENT RESULTS, FUNCTIONAL EQUIVALENCY Sylviane Nibel, Boris Bosdevigie CSTB - Centre Scientifique et Technique du Bâtiment, France Validity determines whether the indicator truly measures what it was intended to measure or how truthful the results are. SuPerBuildings has collected core sustainability indicators suggested by standards and different rating systems. has discussed and analysed the true possibility of these indicators to give information about the sustainability of buildings. SuPerBuildings Final Workshop Brussels Contents Importance of Top-down approach Ensure the validity of indicators Make the assessment results comparable Define the functional as a basis for comparison and benchmarking The outcomes of the research work suggest that a top-down approach should be followed in the selection of indicators in order to ensure the validity of sustainability assessments. Two main criteria for individual indicators: Sustainability indicators of buildings must indicate an issue of concern of sustainable development. Buildings must have a significant impact on that issue of concern

4 Subjects of concern Comparability of assessment results Values Resources Biodiversity Environment Society Economy Stability Ecosystems Climatic systems Values Health Comfort Safety / security Culture Stability Human interactions / relationship Values Economic value Stability Economic risks In order to improve the reliability and comparability of assessment results, we need well defined assessment and calculation methods. SuPerBuildings has selected and developed suitable assessment methods for each indicator in order to enable the reliable assessment of performance levels. SuPerBuildings has identified issues that significantly affect the assessment results. 5 7 Validity: Comparability of assessment results Clear link with sustainability issues of concern Validity is given by the top-down approach used in the elaboration of the SPB framework For each indicator, background information is given about the issue of concern: current situation, phenomenon, trends, EU policies, influent parameters, etc. Attention is drawn to a possible bias given by the indicator versus issue of concern Prerequisites for comparability : detailed and transparent description of the indicator, particularly in terms of system boundaries and calculation method indicator applicability equivalency: comparison of assessment results of 2 buildings needs to be based on the same functional equivalency; if not, the difference between functional s shall be clearly eplained. Comparability may be understood in two ways: for absolute comparison (direct comparison of calculated /measured values) for relative comparison (valuation in a given contet, use of relevant benchmarks based on the same rules, distance-to-target) 6 8 2

5 Comparability (cont d) Other comparability issues We included comparability information into the indicator description format. It eplains under which conditions comparison is possible or not. Comparability is essential for harmonization of indicators between different assessment systems Uncertainty of results and variable data quality/sources may limit comparability 9 As a result: need of consistency among LCA indicators - Energy, CO 2, water, waste, emissions - EeBGuide: provisions and guidance for harmonisation of LCA studies ( How to compare qualitative or composite indicators? Fleibility versus comparability? - Same structure of detailed issues of concern - Same weighting / aggregation - Low level of subjectivity - Two situations have to be distinguished: 1. assessment in an absolute way direct comparison of scores 2. assessment in reference to a local contet and epressed in a relative way (%, contetual points...) comparison in terms of distance-toreference or distance-to-target Eamples of comparability requirements Mainly for LCA indicators: The definition of the functional of the building (cf. standards) needs to be consistent between the buildings to be compared. Attention is drawn on the definition of the floor area taken into account in the indicator unit (m 2 ), because definition of net floor area varies according to the country. System boundaries have to be checked and similar. Regarding the construction products, it is necessary to check that the assessment includes the same families of products (for instance foundations, structure, envelope, distribution, doors and windows, floor coverings). Similar assumptions and methodology for the end-of-life To keep in mind possible local constraints (seismic, geological ) To refer on EU standards, as EN and EN Environmental declarations of energy sources have to be based on the same methodology. equivalency and comparability Why is functional essential for sustainability assessment schemes? What is addressed by this scale? Type of project? Geographical contet? Geological contet? Urban contet? Local requirements and regulation? What building functionality? A functional is needed to describe the object addressed by a benchmark 10 3

6 equivalency and comparability Practical definition of functional According to CEN TC 350 Comparisons between the results of assessments of buildings [ ] shall only be made on the basis of their functional equivalency. For sustainability assessment the same functional shall be used for the assessment of each of the individual dimensions of sustainability A FE is a set of characteristics that form a basis for the comparison of building for Key Indicator developed in sustainability schemes Other parameters not included into the FE should be reported in addition equivalency Classification of parameters that influence Key indicators of sustainability Aspects linked to the location Climate Geological aspects (soil composition) Temperatures (heating degree days, cooling degree days, microclimate due to urban contet...) Rainwater resources Elevation Solar potential Wind (potential for wind turbine production?) load-bearing capacity Topography (eg. Slope of the site ) Presence of radon (eg. Influence IAQ ) Geothermal potential seismic contet availability of water resources on-site Reference unit Indicator of performanc es Indicator related to specific constraints. equivalency and comparability Process to define the functional? equivalency Classification of parameters that influence Key indicators of sustainability What parameters impact on environmental? Purpose of the benchmark? What scope and what precision? Aspects linked to urban contet Referenc e unit Indicator of Indicator related to specific constraints. Parameters for comparability: Use oriented typologies Occupant capacity Size Required Service life Climate Density constraints Security constraints Usability Integrated facilities Included services Equivalent / reference unit Local constraints Declared functional (if not included into social, environmental or economic ) Adjusting performance target for Key Indicators Reporting Indicators of constraints or functional Acoustic aspects constraints linked to noisy environment Urban rules aspects (Town planning..) Access to facilities Economical value of building site National electricity production mi constraints regarding density rules of accessibility for disabled people architectural constraints access to renewable energy (solar) access to heating network access to urban network (gas, electricity...) access to waste water/treatment value of real estate regarding the nearby environment (city-centre, access to urban facilities ) Primary energy factor, CO2 emission factor Others Flooding risks 4

7 equivalency Classification of parameters that influence Key indicators of sustainability Aspects linked to building intrinsic characteristics (functionality, technical aspects...) Reference unit Indicator of Indicator related to specific constraints. use-oriented typology building service life (user requirements, design life) (X) (and X) (or X) number of occupant scenario for occupation Thank you for attention Use aspects age of occupants Services provided: - car park (underground or not) -balcony - garden garden, balcony ) - other floor area (TLA,GFA, NFA, technical area...) sylviane.nibel@cstb.fr boris.bosdevigie@cstb.fr number of floors Size and space aspects height under ceiling (=height of each floor) number of underground levels Indicator of space (m²/pers) Other... SuPerBuildings Final Workshop Brussels equivalency as part of the process of benchmark definition Assessment method of indicators functional Rules for calculation of indicators that enable precision and reproductibility of results. Rules for normalization and aggregation. List of parameters describing the object addressed by the benchmark Other information considered as relevant for the comparison (e.g. indicator of local constraints, declared functional..) Contet and purpose of the benchmark: - Objectives of sustainability; - Political, and economical contet; - Interested groups and stakeholders benchmark values From a bottom-up approach (e.g. statistical eperimentation, calculated values, technical or economical optimum...) From a top-down approach (e.g. needed target to make significant improvement, political target, etc.) 5