Metrology for Thermal Efficiency of Buildings

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To meet the constraints imposed by the Kyoto Protocol on reducing greenhouse gas emissions,the EC Directive 2002/91/EC [1] laid down a series of requirements concerning energy efficiency in new buildings and major renovation of existing buildings. At the end of 2006, the EU pledged to cut its annual consumption of primary energy by 20% by 2020. The European Commission considers the biggest energy savings are to be made in buildings, with savings potentials estimated at 28% by 2020. The energy saving measures for buildings have concentrated either on increasing the thickness of conventional insulation and/or super-insulating materials for existing and new homes, and the upgrading of insulating glazing products. Sadly, the metrology to support the claims of new products is not always reliable and is rarely traceable. Building designers are calling for reassurance that new insulation innovations provide accurate performance data, so that the products specified indeed reduce entire building energy consumption/loss as claimed and meet the regulatory requirement. This need has been highlighted by certain types of new product being sold with exaggerated claims based on measurements made within
universities using techniques that have not been validated or standardised. The resulting controversy has lead to increased industrial calls for reliable measurements of the real in-situ thermal performance of building components.


Measurement of the thermal conductivity of insulating materials by National Metrology Institutes (NMIs) has been traditionally based on small samples about 300 X 300 mm with thicknesses of up to 150 mm. This has made it difficult to accurately measure both conventional materials and new insulating materials such as wood fibre and multifoils which are often very spatially inhomogeneous. Further measurement problems are created by some super-insulating products (eg evacuated panels and aerogels) which have high or very high thermal resistances and which are also non-homogeneous. In addition standard, small test samples cannot be cut from many of these innovative products for fear of destroying their insulating performance, and thus these materials cannot be accurately measured as they exit a production process and so quality control is compromised.


The emissivity of coated glass panes has been determined by measuring the near normal regular spectral reflectance in the spectral range from 5 ým to 50 ým in accordance with the documentary standard EN12898:2001 [3]. Those spectral reflectance measurements are performed by comparison to calibrated mirrors, using infrared spectrometers (mostly FTIR) fitted with specular reflectance accessories. Thus the availability of capabilities for calibration of infrared spectral reflectance should be permanently maintained by one (or more) NMI in EU. At present, it appears that no European institution is able to easily perform traceable calibration in spectral reflectance over the 5 ým to 50 ým spectral range or to supply reference mirrors calibrated over that range.

 

Source:
Description of the Call for Joint Research Projects for ENERGY 2009 Topic 2 Metrology for Thermal Efficiency of Buildings, EURAMET - European Association of National Metrology Institutes
Link to full-version:
http://www.emrponline.eu/energycall/docs/srt/srt02.pdf

 


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