energy assessment / audit

This is explained in detail in annex I.5 of the standard EN ISO 13790. The main difference is that the degree day method contains an implicit assumption about the effect of internal and solar gains on the heat balance (independent of the specific building), while this effect is explicitly taken into account in the monthly method (as a function of the building parameters). Question submitted by: Dick van Dijk (TNO, The Netherlands) Anwered by: Dick van Dijk (TNO, The Netherlands) Date: 21/10/2009
Post date: 21 Oct 2008
Type: Ask the Experts

Each method has its own applications: the seasonal method is the simplest, but it is applicable only in climates where seasons are clearly defined, the monthly method is easy to use in buildings without or with small intermittence effects, while the simple hourly method is of more general use, but requires hourly meteorological and use data and, despite the fact that it produces hourly results, it is based on a simplified model with only the monthly results validated.
Post date: 21 Oct 2008
Type: Ask the Experts

Background information on the origin and rationale of the monthly method can be found in Annex I of the standard EN ISO 13790. It also contains more technical information concerning the content of EN ISO 13790, as well as Annex H of the standard EN ISO 13790 and the bibliography at the conclusion of the standard. Question submitted by: Dick van Dijk (TNO, The Netherlands) Anwered by: Dick van Dijk (TNO, The Netherlands) Date: 21/10/2008
Post date: 21 Oct 2008
Type: Ask the Experts

There is a consensus within Europe that the built environment has a major task to reduce the CO2 emissions and convert to sustainable energy systems. The energy saving targets are high and there is a need to show in a non controversial way the achievement of the various Member States. This is one of the reasons that harmonised calculation procedures, including harmonised input parameters, are desirable.
Post date: 10 Mar 2008
Type: Ask the Experts

This is possible if not only the overall energy performance (in MJ or kWh), but also the system energy performance is reported separately. The same goes for the local production of renewable energy. EN 15603 describes how this could be done. Given the different lifespan of building elements and building systems separate consideration would be beneficial. Question submitted by: Dick van Dijk (TNO, The Netherlands) Anwered by: Dick van Dijk, TNO and Jaap Hogeling, ISSO (The Netherlands) Date: 10/03/2008
Post date: 10 Mar 2008
Type: Ask the Experts

The energy performance of products is taken into account in an indirect way. The EPBD CEN standards are generally dealing with performance description of buildings and systems. The EPBD standards describe the way the system performance has to be determined. These values are influenced by the relevant product specifications. The standards developed under the EPBD either refer to relevant product standards or specify the required input for the system standards.
Post date: 9 Mar 2008
Type: Ask the Experts

This is up to the National Standard Body, most countries offer both possibilities. Question submitted by: Dick van Dijk (TNO, The Netherlands) Anwered by: Dick van Dijk, TNO and Jaap Hogeling, ISSO (The Netherlands) Date: 2008/03/10
Post date: 9 Mar 2008
Type: Ask the Experts

EN ISO 13790 describes calculation methods for the energy need for heating and cooling for each building zone, whereas EN 15603 deals with the overall energy use and the energy performance of buildings, collating the results from other standards, including those from EN ISO 13790. More information: CENSE Information Paper P095 which can also be downloaded from the BUILD UP Portal. Question submitted by: Dick van Dijk (TNO, The Netherlands) Anwered by: Anna Staudt and Hans Erhorn, Fraunhofer Institute of Building Physics (Germany) Date: 2008/02/04
Post date: 4 Feb 2008
Type: Ask the Experts

The primary advantage of the more detailed and thus more advanced method (holistic approach) is the higher quality and reliability of the results, due to the very realistic model on which the calculation is based. The intermediate results are quite exact and very appropriate for further more detailed analysis. Its main disadvantages are the need for suitable computer software for the complex calculation and the longer time required to perform the calculation.
Post date: 4 Feb 2008
Type: Ask the Experts