Barriers to natural ventilation Work Package 1Perceived Barriers toNatural Ventilation Designof Office Buildings Objective • The objective of the study was to identify perceived barriers restricting the implementation of natural or simple fan assisted ventilation systems • in the design of new office buildings and • in the refurbishment of existing office buildings. Interviews RESULTS of interviews Knowledge Experience Guidelines & products User satisfact. Performance Controllability Costs Future Restrictions Design Conclusions & recommendations More... NatVent
Interviewsinterviewees • Interview of 107 designers and decision makers: • 42 architects • 24 consultant engineers • 11 contractors • 9 developers • 14 owners • 7 governmental decision makers
Interviewsquestionnaires • Structured interviews based on questionnaires. • Questionnaires completed by the interviewee and the interviewer together. • Focus on: • general knowledge • viewpoints • experience and • perceived problems. • Focus on decisions actually taken in specific building projects. • Allows for additional comments, remarks and viewpoints.
Interviewsusers • Interviews with users of office buildings are not included in this study. • The users perception is part of Work Package 2: ‘Performance of naturally ventilated buildings’, where physical parameters are also measured and compared with the users responses.
N DK S NL B UK CH InterviewsCountries & Climates • 7 central and north European countries with moderate or cold climates: • Belgium (B) • Denmark (DK) • Switzerland (CH) • Norway (N) • The Netherlands (NL) • Sweden (S) • United Kingdom (UK)
5 4 Mech. vent. Trad. NatVent 3 Spec. NatVent None Thorough 2 1 All Owners Develop. Contract. Architects 0 Gov. Dec. Cons.eng. Perception of own knowledge • A specific 5 point scale ranking from 1: None to 5: Thorough is used to indicate the level of knowledge. • All is the average of all groups except the governmental decision makers, with the professional groups weighted equal. • Nearly all the interviewees know less about specially designed natural ventilation than they know about mechanical ventilation. • On average the interviewees have nearly the same level of knowledge of traditional natural ventilation as on mechanical ventilation.
100 B 80 DK CH 60 N Per cent NL S 40 UK All 20 0 Mech. vent. Trad. NatVent Spec. NatVent The interviewees’ experience • Most of the interviewees have considerable experience of mechanical ventilation. • Many of the interviewees have worked with traditional natural ventilation. • Their experience with special designed natural ventilation is very limited. • The relative experience is the per cent of mechanical or natural ventilated offices designed, constructed or owned.
Guidelines & products • Nearly all of the interviewees reported that design guidelines and products were more readily available for mechanical ventilation systems than natural ventilation systems. • The general opinion among the interviewees is that there are few good sources of information about natural ventilation • A specific 5 point scale ranking from 1: Poor to 5: Excellent is used to indicate the interviewees’ perceptions
Expected user satisfaction • On average, the interviewees expect the same level of user satisfaction for naturally and mechanically ventilated cellular offices. • The interviewees expect higher level of user satisfaction in natural ventilated cellular offices than in natural ventilated open plan offices. • The level of user satisfaction expected In mechanically ventilated offices is the same as in cellular offices as in open plan offices. • A specific 5 point scale ranking from 1: Poor to 5: Excellent is used to indicate the expected user satisfaction
Expected performance in practice • In general, the interviewees expect mechanical ventilation systems to perform better than natural ventilation systems with regard to cooling effectiveness, draught minimisation, ability to remove odours, ability to prevent ingress of odours and ability to insulation against external noise. • Regarding the generation or transmission of internal noise the interviewees expect the same level of performance from both types of ventilation system.
Expected controllability • In general the interviewees expect a high degree of centralised control with mechanical ventilation systems and less centralised control of natural ventilation systems: especially in cellular offices. • The level of local and individual control of ventilation expected is higher in cellular offices than in open plan offices.
Expected costs • Most interviewees expect higher installation, higher running and higher maintenance costs for mechanical ventilation than for natural ventilation. • If mechanical ventilation is installed in a building it will account for a significant proportion of the total construction costs. • Installation costs for a natural ventilation systems could be high if the system requires chimneys, more floor area or additional volume. • A specific 5 point scale ranking from 1: Inexpensive to 5: Expensive is used to indicate the interviewees’ perception of the costs.
Expected future use of natural ventilation • In general, architects have the highest expectations of the increasing use of natural ventilation in offices. • On an average basis, it is only the governmental decisions makers who anticipate a decrease in the use of natural ventilation. • The expectation is indicated on a specific 5 points scale ranking from 1: Significant decreasing over 3: Unchanged to 5: Significant increasing. • All is the average of all groups except the governmental decision makers, with the professional groups weighted equal.
Perceived restrictions in regulations, codes, norms and standards • The perception that regulations limit the use of natural ventilation varies from country to country. • In Belgium, Norway and Sweden the interviewees report that there are significant barriers to the use of natural ventilation. • In other countries, such restriction are perceived to be more limited. • The perception of restrictions is indicated on a specific 5 points scale ranking from 1: None to 5: Comprehensive
Critical parameters for the design • Each interviewee was allowed to point out a maximum of 5 critical parameters and was asked to prioritise them from 1: Low to 5: High.
The most critical parameters • For many of the interviewees the most critical parameter is summer-time room temperature or construction costs. • Other give the highest priority to solar heat gains, indoor air quality and indoor pollution. • Several of the interviewees identified external noise and operation costs parameters.
Influence on design • Architects, consultant engineers and owners have the greatest influence on the choice of design. • Each interviewee was allowed to point out a maximum of 5 persons or conditions and was asked to prioritise them from 1: Low to 5: High.
Conclusions & Recommendations • The interviews identify significant lack of knowledge and experience of specially designed natural ventilation in office buildings compared to the knowledge and experience of mechanical ventilation.
Conclusions &Recommendations • Simple, energy efficient, low cost natural ventilation system concepts for new and refurbished office buildings have to be developed. • Standards and guidelines must be developed so that there is a more favourable technical and legal framework for naturally ventilated office buildings. • Simple design tools: diagrams or easy - to - use computer programmes have to be developed. • Components and control systems for natural ventilation have to be improved. • General knowledge on natural ventilation has to be improved.
You can read and print pdf-files with the Acrobat® Reader ®3.0. Program. This program is free. Download it from the Acrobat web site: www.adobe.com OR run the installation file ar32e301(1).exe in the directory \Installation Barriers to natural ventilation More information... Objective Interviews The European barrier report and the different national barrier reports (pdf-files) can be found on the CD-rom in the directory /Reports/Barriers/… RESULTS of interviews Knowledge Experience Guidelines & products User satisfact. Performance Controllability Costs Future Restrictions Design Conclusions & recommendations More... NatVent