Article 4 of the EPBD stipulates explicitly that attention should be paid to indoor climate conditions: “Member States shall take the necessary measures to ensure that minimum energy performance requirements for buildings are set … These requirements shall take account of general indoor climate conditions, in order to avoid possible negative effects…”.

This is also listed in the annex of the EPBD: “The methodology of calculation of energy performances of buildings shall include…

(d) ventilation;…

(h) natural ventilation;…

(i) indoor climatic conditions, including the designed indoor climate.”

Whereas in the past the major challenge was to keep our buildings sufficiently warm, nowadays the challenge is in guaranteeing reasonable comfort conditions in summer without (or with minimum) cooling energy. It is therefore important that building designers and other stakeholders understand the thermal behavior of a building and its occupants and are aware of the available alternative techniques that substantially improve the comfort in the building and significantly decrease (or even eliminate) energy consumption. For example, solar and thermal control techniques, heat amortisation and heat dissipation techniques have been proven to be extremely efficient and may decrease the cooling load of buildings up to 80 %.

Mechanical ventilation and air conditioning control the indoor conditions with a specific high consistency range that is independent of external conditions, whereas passive systems cannot be regulated that precisely and quickly. However, passive cooling makes proper use of the existing natural possibilities and principles, uncharged by side effects, thus simulating better the natural conditions, providing a feeling of comfort and using less to no energy. 

Based on the idea that the human body continually adapts to a variety of conditions, an adaptive standard, would not include fixed indoor parameters but, would aim to promote (easy) adaptation by using the following principles:

·         People adapt more easily to the temperatures they are most familiar with. The range of conventional temperatures is population related and depends on geography, culture (customs) and climate. Therefore, the adaptive standard would define a range of conventional temperatures for each specific population and building type at different seasons of the year.

·         Adaptation is easier under more or less stable conditions. An adaptive standard would indicate which degree of stability of indoor conditions is required and how to achieve this.

·         A building may or may not provide opportunities for user friendly adaptation and control over the thermal environment. The adaptive standard would prescribe which opportunities for control are required (f.e. openable windows, temperature or solar controls, etc.) 

The adaptive approach is beginning to influence standards and guidelines for comfort in buildings, as is evident from the use of field results in ASHRAE Standard 55-2004 (ASHRAE, 2004) and (in the UK) the CIBSE (Chartered Institute of Building Services Engineers) Guide (CIBSE, 2006).

Adaptive comfort builds on the principle that people experience differently and adapt, up to a certain extent, to a variety of indoor conditions, depending on their clothing, their activity and general physical condition. Therefore, contrary to the conventional cooling which is based on pre-calculated temperatures and humidity levels, the adaptive approach is based on a non fixed set of conditions, taking into account thermal perception and behavior of the user, requiring him to take an active role in controlling his indoor environment.

The main international guidelines and standards on thermal comfort are:

·         International Standard ISO 7730. This standard is based on Fanger’s Predicted Mean Vote (PMV), which predicts the mean thermal sensation of a group of people, and the Predicted Percentage of people Dissatisfied with the environment (PPD).

·         ASHRAE 55 defines conditions that are being considered satisfactory for a specific percentage of users, including calculation methodologies for thermal comfort based on PMV/PPD

·         CEN 15251: Criteria for the indoor environment including thermal, indoor air quality, light and noise. The CEN standard defines minimum ventilation requirements, minimum and maximum indoor temperatures that can be used for energy calculation, assessment and certification. It is different than prescribed standards because it makes a difference between mechanically ventilated systems and naturally ventilated systems. For buildings without mechanical ventilation /cooling, alternative methods are proposed.

These guidelines and standards specify comfort in a broader sense that is easier to refer to and often stem from numerous more detailed and sophisticated guidelines and standards (normative references) such as:

·         ISO 7243, Hot Environments – Estimation of the heat stress on working man, based on the WBGT Index (wet bulb globe temperature)

·         ISO 7726, Ergonomics of the thermal environment — Instruments for measuring physical quantities

·         ISO 7933, Ergonomics of the thermal environment — Analytical determination and interpretation of heat stress using calculation of the predicted heat strain

·         ISO 8996, Ergonomics of the thermal environment — Determination of metabolic rate

·         ISO 9920, Ergonomics of the thermal environment — Estimation of the thermal insulation and evaporative resistance of a clothing ensemble

·         ISO 10551, Ergonomics of the thermal environment — Assessment of the influence of the thermal environment using subjective judgement scales

·         ISO 11399, Ergonomics of the thermal environment — Principles and application of relevant International Standards

·         ISO TR 11079, Ergonomics of the thermal environment — Analytical determination and interpretation of cold stress using calculation of the required clothing insulation (IREQ) and the assessment of local cooling effects

·         ISO 13731, Ergonomics of the thermal environment — Vocabulary and symbols

·         ISO/TS 13732-2, Ergonomics of the thermal environment — Methods for the assessment of human responses to contact with surfaces — Part 2: Human contact with surfaces at moderate temperature

·         ISO/TS 14415:, Ergonomics of the thermal environment — Application of International Standards to people with special requirements

·         Humphreys, M.A. and Nicol, J.F. (1998) Understanding the Adaptive Approach to Thermal Comfort, ASHRAE Transactions 104 (1) pp 991-1004

·         DeDear (2004), Thermal Comfort in Practice. Indoor Air Journal. Vol 14. Supplement 7, pp 32-39.

·         McCartney K.J and Nicol J.F. (2002) Developing an Adaptive Control Algorithm for Europe: Results of the SCATs Project. Energy and Buildings 34(6) pp 623-635

The general tendency on summer comfort should be to use the best available practical means, including alternative techniques, to control the indoor environment and provide stable indoor conditions in order to avoid discomfort, using the least possible energy. 

In line with the principle of equivalence, each Member State implements various EN standards into its regulations to assist in the evaluation of the performance of alternative cooling techniques. Examples of such standards are:

·         EN 13790: Energy performance of buildings-Calculation of energy use for space heating and cooling

·         EN 15241: Calculation methods for energy losses due to ventilation and infiltration in commercial buildings

·         EN 15242: Calculation methods for the determination of air flow rates in buildings including infiltration

As has already been done for centuries before us, good indoor climate conditions during summer can be achieved through efficient use of the physical and natural conditions and sources around the building such as its position and orientation, the relief, the climate, the vegetation, the wind direction, air velocity etc. During design of the building such parameters need to be taken into account to prevent the building from overheating, by using proper materials, making efficient use of windows and openings, providing sufficient shading, night cooling, etc. Occupants should also be provided with control over their environment like for example openable windows and manual override on control systems to ensure satisfaction and increased adaptation levels during hot spills.  

This is defined in EN 13829, § 6.1.2. All exterior surfaces, plus floors, ceiling and walls to neighbouring apartments are taken into account.
However, other assumptions are used in some countries to extract indicators that better fit the national requirements of the EP-regulations (see question regarding the measurement of multi-family buildings).

Anwered by: Rémi Carrié and Gaëlle Guyot (CETE de Lyon)
Date: 2008/12/12

Measurements usually show that light (e.g., timber-frame or steel) constructions are leakier than massive construction, but this is not bound to be. In fact, PassivHaus houses are often light constructions and are very airtight.

The general statement that can be drawn is that light constructions are more sensitive as the airtight layer can be more affected by poor design and workmanship than in massive constructions.

Anwered by: Rémi Carrié and Gaëlle Guyot (CETE de Lyon)
Date: 2008/12/12

The SAVE-DUCT project has shown that there are large discrepancies between countries on this subject (the project report is available through AIVC at www.aivc.org). Analyses performed on measurements results have shown that Belgian and French ductwork systems were typically 3 times leakier than Class A whereas Swedish systems commonly complied with Class B (i.e., 3 times tighter than Class A). The main reason is that the Swedish quality system (Boverket) imposes a rather pragmatic testing scheme which has encouraged the systematic use of ductwork with pre-fitted seals that guarantee good airtightness. This type of ductwork is very much used in Nordic countries where similar conclusions can be drawn.
This topic will be discussed in more detail during the next ASIEPI WP 5 Web Event in October 2009.

Anwered by: Rémi Carrié and Gaëlle Guyot (CETE de Lyon)
Date: 2008/12/12

To our knowledge, the UK is the only country that has made testing mandatory. This has been in force since 2002 for large buildings and extended to most buildings in 2006.

Anwered by: Rémi Carrié and Gaëlle Guyot (CETE de Lyon)
Date: 2008/12/12

The airtightness measurement of single apartments is usually performed the same way as in individual houses. Therefore, there is no specific protocol to balance the pressure between the apartment under test and other apartments. Different protocols may lead to very different results.

Anwered by: Rémi Carrié and Gaëlle Guyot (CETE de Lyon)
Date: 2008/12/12

There is little information on the subject at the moment. A study referenced in a paper written by Erhorn et al. and presented at the 2008 AIVC conference shows airtightness values of 31 “PassivHaus” houses at commissioning and 2 year later. The average n50 at commissioning and 2 year later were 0.37 and 0.46 ach at 50 Pa, respectively.

Anwered by: Rémi Carrié and Gaëlle Guyot (CETE de Lyon)
Date: 2008/12/12

Measuring or evaluating the airtightness of multi-family buildings is challenging as there may be technical and practical difficulties that prevent from pressurizing the whole building. These difficulties include for instance building configuration (e.g., exterior hall ways that do not allow pressurisation from a single point), pressurisation fan size, stack effect, or cost.
Therefore, the measurement of the whole envelope of multi-family buildings is rarely performed in practice. However, several countries use alternate schemes to overcome these problems, for instance:
- in France, in the framework of the BBC-Effinergie label, the measurement can be performed by apartment. The basic idea is to test a sample (e.g., of 3 units for a building of 30 apartments or less) and to make a weighted average of the results to estimate the global airtightness.
- in Norway, tests on single apartments can be used. It is seen as a simple practical measure that also encourages airtightness between apartments, which is good to avoid noise and cross-contamination.

Anwered by: Rémi Carrié and Gaëlle Guyot (CETE de Lyon)
Date: 2008/12/12

There exists a certification scheme in Germany which is not compulsory to perform tests.
There exists a compulsory authorisation process in France for technicians who perform test on BBC-Effinergie buildings.
To our knowledge, there is no other certification or authorisation scheme in European countries.

Anwered by: Rémi Carrié and Gaëlle Guyot (CETE de Lyon)
Date: 2008/12/12

There is no up-to-date document at this time.

Anwered by: Rémi Carrié and Gaëlle Guyot (CETE de Lyon)
Date: 2008/12/12

To our knowledge, only two low-energy labels include a minimum requirement for low-energy buildings:
- the PassivHaus standard (www.passivhaus.de) that requires an airtightness better than 0.6 air changes per hour at 50 Pa (n50 <= 0.6 ach);
- the BBC-Effinergie standard (www.effinergie.org) that requires for an individual house an airtightness better than 0.6 m3/h per m2 of cold surface area at 4 Pa (this translates for an individual house to a n50 of about 2.5 ach).
Although a minimum requirement is not imposed, the global energy use requirements of low-energy labels encourage to achieve good envelope airtightness. Problems may arise when an appropriately set default value can be used, allowing buildings to be labelled although their airtightness is much worse than the default value.

Anwered by: Rémi Carrié and Gaëlle Guyot (CETE de Lyon)
Date: 2008/12/12

Now in Europe, many countries have adopted the n50 value (i.e., the leakage flow divided by the volume) for their EP regulation while others (e.g., Belgium, France, UK) use the envelope area normalisation. The rationale behind this latter choice lies in the fact that the volume is not needed for an energy performance calculation. Using the n50-value should require a precise definition of the way the volume is calculated, which to our knowledge, is not the case in any European country. On the other hand, the envelope area is usually well-defined in regulations.
More generally, the indicator used may be different depending on the application. The volume normalisation seems well-appropriate to pollutant transfer applications as the volume is a necessary input. Similarly, the exterior envelope area indicator seems well-appropriate to energy use applications. The floor-area normalisation may be interesting for comparison purposes as it is often more difficult to have access to the volume or envelope area data than the floor-area.

Anwered by: Rémi Carrié and Gaëlle Guyot (CETE de Lyon)
Date: 2008/12/12

To some extent yes. A collection and analysis of some data collected through the ASIEPI partners has been presented at the 2008 BlowerDoor conference (Papaglastra et al., 2008). However, caution should be exercised when comparing airtightness values :
- the measurement methods are not necessarily the same. EN 13829 mentions two methods (A and B) that can lead to very different results e.g., depending on how combustion appliances are sealed; (*)
- the calculation of the volume or the envelope area that is used to normalise the leakage flow may be different for the same building, depending on the assumptions adopted nationally or even by the operator.
It would be useful to harmonise these methods to be able to reliably compare and monitor results.

(*) In Belgium, additional specifications for the measurement of envelope airtightness have been published (http://www.epbd.be/go/airtightness-measurement)

Anwered by: Rémi Carrié and Gaëlle Guyot (CETE de Lyon)
Date: 2008/12/12

There are three major ways to estimate this impact:
- the simplest is to evaluate the infiltration losses based on a rule of thumb established by Drubul in 1988 (*) and suggested by Kronvall (**) in 1978. The rule says that the infiltration airflow rate in air changes per hour may be determined by dividing the n50 value by an empirical coefficient that lies between 10 and 30. In practice, the empirical coefficient is often set to 20 (i.e., the infiltration airflow rate is equal to the airtightness at 50 Pa divided by 20);
- an intermediate approach is to estimate the infiltration airflow rate based on the empirical model proposed in ISO 13790, annex G;
- a more detailed approach is to perform and hourly simulation of the airflow rates, based on a pressure network code such as that described in EN 13465.
Once the infiltration airflow rate is known, the calculation of the energy losses is straightforward.
In national regulations, one of those three methods is commonly used in the EP-calculation.

(*) Drubul C, Inhabitant’s behaviour with respect to ventilation, Technical note 23, Air Infiltration and Ventilation Center, 1988
(**) Kronvall J, Testing of houses for air-leakage using a pressure method, ASHRAE trans. Vol 84 no 1 1978

Anwered by: Rémi Carrié and Gaëlle Guyot (CETE de Lyon)
Date: 2008/12/12

Energy wastage due to envelope leakage has been estimated in various countries through numerical simulations:
- in Belgium and in Germany, the energy impact has been calculated to be about 10% of the energy performance level for individual houses;
- estimates based on simulations on 9 real buildings in France lie between 0.5 and 15 kWh-pe/m2 per year (depending on climate, ventilation system type, and building configuration), with an average of 6.6 kWh-pe/m2, between “default” and excellent airtightness

For comparison purposes, in Belgium, France and Germany, the impact of good envelope airtightness is similar to that of solar collectors for domestic hot water.

Anwered by: Rémi Carrié and Gaëlle Guyot (CETE de Lyon)
Date: 2008/12/12