Indoor environmental input parameters for the design and assessment of energy performance of buildings

Bjarne W. Olesen

Ph.D.

Fellow REHVA and ASHRAE

International Centre for Indoor Environment and Energy

Department of Civil Engineering

Technical University of Denmark

bwo@byg.dtu.dk

EN16798-1 is the future European standard dealing with all indoor environmental parameter, replacing EN 15251. Within the new set of EPB standard, EN16798-1 is essential for the whole calculation of energy performance of buildings and related certification safeguarding acceptable indoor environmental quality. While the standard will be out for formal vote on January 2018, its accompanying technical report CEN TR 16798-2 has already been accepted. The formal acceptance of both documents will enable EU experts to benefit of a holistic approach to buildings energy performance calculation.

Keywords: EPB standards, prEN16789-1, CEN TR 16798-2, Indoor environmental parameters

The first international standard that dealt with all indoor environmental parameters (thermal comfort, air quality, lighting and acoustic) was published in 2007 as EN15251. This standard prescribed input parameters for design and assessment of energy performance of buildings and was a part of the set of standards developed to support the implementation of the Energy Performance of Buildings Directive in Europe.

This standard was revised and issued for public comments with a new number: prEN16798-1. Besides the standard, a Technical Report, 16789-2, is also being developed to support and explain in more details the standard. There were many comments received and the document was revised for formal vote Fpr16798-1 in 2016. Unfortunately, the standard was with a small margin not-accepted whereas the Technical Report was accepted. The reasons for not-acceptance were for some countries technical and significant problems with the format, that unfortunately was changed and did not comply with the basic rules for the EPBD-standards.

Both documents have now gone through an editorial review so that they fulfill the basic format requirements. A new formal vote will start in January 2018. There are no fundamental technical changes compared to the versions voted on early 2017.

The standard prEN16798-1

The scope of the standard is:

·         to specify requirements for indoor environmental parameters for thermal environment, indoor air quality, lighting and acoustics and specify how to establish these parameters for building system design and energy performance calculations.

·         to include design criteria for the local thermal discomfort factors, draught, radiant temperature asymmetry, vertical air temperature differences and floor surface temperature.

·         to be applicable where the criteria for indoor environment are set by human occupancy and where the production or process does not have a major impact on indoor environment.

·         to specify occupancy schedules to be used in standard energy calculations and how different categories of criteria for the indoor environment can be used.

·         to be used in national calculation methods. This standard sets criterion for the indoor environment based on existing standards and reports listed under normative references or in the bibliography.

·         not to specify design methods, but to give input parameters to the design of building envelope, heating, cooling, ventilation and lighting.

This standard is essential for the whole calculation of energy performance of buildings and related certification. The standard is now written in normative language and should be clearer as all the informative text will be included in the technical report. The standard does include default criteria in three or four categories for the various indoor environmental parameters. These default values are included in a series of tables in an informative Annex B. Individual countries can decide if they want to use these default values, only use one category, or use quite different values, which will be included in a normative national Annex A with similar structure as Annex B.

The calculated energy performance and energy use of buildings depends significantly on the criteria used for the indoor environment (heating, cooling, ventilation and lighting) and building (including systems) design and operation. Indoor environment also affects health, productivity and comfort of the occupants. Recent studies have shown that costs of poor indoor environment for the employer, the building owner and for society, are often considerably higher than the cost of the energy used in the same building. It has also been shown that good indoor environmental quality can improve overall work and learning performance and reduce absenteeism. In addition, uncomfortable occupants are likely to take actions to make themselves comfortable which may have energy implications. There is therefore a need for specifying criteria for the indoor environment for design and energy calculations for buildings and building service systems.

The present standard specifies how design criteria shall be established and used for dimensioning of systems. It defines how to establish and define the main parameters to be used as input for building energy calculation. The standard also gives default criteria for design and energy calculations in an informative Annex B. A similar normative Annex A is included for specifying national criteria in a normative way. The national Annex A may specify different criteria for design compared to criteria for energy calculation. The national annex may also specify different criteria for different building types (offices, schools, hospitals, new, existing, etc.).

The present standard does not require certain criteria to be used. This is up to national regulations or individual project specifications.

The corresponding technical report CEN TR 16798-2

The full title of the corresponding technical report is: TR 16798-2: Energy performance of buildings — Part 2: Indoor environmental input parameters for design and assessment of energy performance of buildings addressing indoor air quality, thermal environment, lighting and acoustics — Module M1-6 — Technical report — interpretation of the requirements in EN 16798-01.

The document has a completely informative nature and its scope is:

·         to deal with the indoor environmental parameters for thermal environment, indoor air quality, lighting and acoustic.

·         to explain how to use EN 16798-1 for specifying indoor environmental input parameters for building system design and energy performance calculations.

·         to specify methods for long term evaluation of the indoor environment obtained as a result of calculations or measurements.

·         to specify criteria for measurements which can be used if required to measure compliance by inspection.

·         to identify parameters to be used by monitoring and displaying the indoor environment in existing buildings. This Technical Report is applicable where the criteria for indoor environment are set by human occupancy and where the production or process does not have a major impact on indoor environment.

·         to explain how different categories of criteria for the indoor environment can be used.

The Technical Report is a guide to EN 16798-1 and can help the users in application of the standard and provide them additional background information. Besides this, the Technical Report describes and recommends additional topics related to the evaluation of the indoor environmental quality and new possibilities to improve the indoor environmental quality and reduce energy use of buildings like personalized systems, air cleaning technologies, consideration of adapted persons, etc.

The Technical Report explains how design criteria can be established and used for dimensioning of systems. It explains how to establish and define the main parameters to be used as input for building energy calculation and long-term evaluation of the indoor environment. The Technical Report also describes how gas phase air cleaning in the future can improve the indoor air quality and partly substitute for outside air. Finally, it identifies parameters to be used for monitoring and displaying of the indoor environmental conditions. Different categories of criteria can be used depending on type of building, type of occupants, type of climate and national preferences. The report explains how these different categories of indoor environment can be individually selected as national criteria, be used in project agreement for design criteria and for displaying the yearly building performance in relation to indoor environmental quality. The designer can also define other categories using the principles from EN 16798-1 and the Technical Report.

In parallel a similar work has been going on within ISO under a joint working group between ISO TC163 and ISO TC205. During the formal vote on ISO level, both documents ISO 17772-1 and TR 17772-2 have been accepted. The two documents are now being printed.

A future goal is to combine the CEN and ISO documents into an ISO-EN standard and technical report.

It is however of outmost importance that FprEn16798-1 is accepted at this second formal vote, to enable us to have a complete set of standards for energy performance evaluation of buildings and that can help to safeguard an acceptable indoor environmental quality.