1. Are Naturally Ventilated Office Spaces Best For New Zealand Climate?
Presented by:
Dr. Eziaku O. Rasheed
Massey University

2. NZ climate
Most of New Zealand are estimated to exceed a mean 2 degrees temperature rise by 2090 and that average temperatures may rise by 1 degree by 2040.
An insecure supply of electricity and greater cooling load.
Buildings will require more energy for cooling systems that rely on electricity.
Future-proof our buildings with adaptive opportunities for passive, low energy buildings
NIWA. Climate Change Scenarios for New Zealand. Accessed 30th April, 2017
Byrd H. Energy Climate Building: An introduction to Designing Future-Proof Buildings in New Zealand and the tropical Pacific. University of Auckland – Transforming Cities, 2012.
Kwok, A.; Rajkovich N. Addressing climate change in comfort standards. Building and Environment 2010, 45,

3. Green office spaces and Natural ventilation
Green office spaces are purported to provide an indoor environment that is expected to be environmentally sustainable with a conducive IEQ for occupants’ use.
Natural ventilation is an element that is often associated with environmental sustainability or Green architecture.
wind and
thermal buoyancy

4. Issue
Despite various evidence that naturally ventilated spaces are environmentally sustainable and provide thermal comfort, it is not a popular indoor environment control system used in New Zealand office environments.
Onyeizu, E. Can Architecture increase productivity? The case of green certified buildings. PhD Thesis, University of Auckland
Russell, A. P., & Ingham, J. M. Prevalence of New Zealand's unreinforced masonry buildings. Bulletin of the New Zealand Society for Earthquake Engineering 2010, 43(3), 182.

5. Aim
we investigated why natural ventilation is not a common indoor environment control system in Green offices buildings in New Zealand

6. Objectives Objective 1:
Ascertain whether the NZ Green building rating tool encourages natural ventilation in office spaces.
Objective 2:
Investigate experts opinion on the suitability of natural ventilation in NZ office spaces.

7. Significance
to provide a background for further study on the implications of the use of natural ventilation to create resilient indoor environments for office buildings.
the greater shift from dependence on mechanical systems to free running environmental control systems.

8. Method
Reviewed the New Zealand Green Star rating tools with a focus on the criteria for thermal comfort in the Green Star Office 2009 version.
Interviewed professionals who have researched on or worked with the concept of natural ventilation in the design of office spaces.
Ten participants (academia and registered architects)
The interview was carried out through a face-to-face meeting, skype call and depending on the location of the respondents.
Reviewed the New Zealand Green Star rating tools with a focus on the criteria for thermal comfort in the Green Star Office 2009 version. The purpose for this is to ascertain whether the criteria encourage the use of natural ventilation in Green office spaces.
This is supported by an interview with professionals who have researched on or worked with the concept of natural ventilation in the design of office spaces. This group of participants was selected as they have sufficient knowledge and experience in this field.
Ten participants (academia and registered architects) were interviewed from tertiary institutions and architectural firms in New Zealand with at least ten years’ experience in the field.
The interview was carried out through a face-to-face meeting, skype call and depending on the location of the respondents.

9. Credit Criteria Summary
Findings: Objective 1
The NZ Green Star IEQ criteria for thermal comfort encourage air conditioning systems over natural ventilation.
Ref No.
Title
Aim of Credit
Credit Criteria Summary
Points awarded
IEQ-6
Thermal Comfort
To encourage and recognise the use of thermal comfort assessments to guide design options.
Up to three points are awarded where it is demonstrated that assessments have been made of thermal comfort levels and used to evaluate appropriate servicing options.
The following Predicted Mean Vote (PMV) levels, calculated in accordance with ISO 7730, (or equivalent using Draft ASHRAE Comfort Standard 55 and "Developing an Adaptive Model of Thermal Comfort and Preference - Final Report on ASHRAE RP884"), must be achieved during Standard Hours of Occupancy and using standard clothing, metabolic rate and air velocity values for 90% of the year
For mechanically ventilated and mixed-mode buildings:
One Point = PMV levels are between -1 and +1
Two Points = PMV levels are between and and
Three Points = PMV levels are between -0.5 and +0.5.
For naturally ventilated buildings:
Two Points = PMV levels are between -1 and +1 and
Three points = PMV levels are between and
- New Zealand Green Building Council, Green Star NZ Technical Manual (vs3.1) Available online: (Accessed 29/03/2017).

10. Thermal comfort criteria
Temperature standards are based mainly on the Predicted Mean Vote (PMV) standards of comfort
More points as the range of temperatures are narrowed
Adaptive method follows the PMV approach sine points are awarded based on PMV measurements.
Easier to obtain more points by merely installing HVAC equipment creates an imbalance
The NZ Green Star tool requires temperature standards that are based mainly on the Predicted Mean Vote (PMV) standards of comfort.
It allocates more points as the range of temperatures are narrowed (3 points for PMV levels between -0.5 and +0.5 for mechanically ventilated and mixed-mode buildings and and for naturally ventilated buildings).
It is inferred that the Adaptive method follows the PMV approach sine points are awarded based on PMV measurements.
While the points awarded for an air conditioning system is the same as those awarded for natural ventilation, the ease at which these points can be obtained by merely installing HVAC equipment creates an imbalance

11. PMV versus Adaptive Model
LEGEND:
External environment
Building Structure
Building materials
Air conditioning systems
Optimum comfort levels of thermal environment based on PMV Model (promoted by NZ Green rating tool)
Extreme IEQ
Adaptive IEQ
Flattening the curve towards a straight line (Optimum comfort levels of temperature)
- Onyeizu, E. Can Architecture increase productivity? The case of green certified buildings. PhD Thesis, University of Auckland

12. PMV model for NV office spaces?
the PMV model is a ‘static’ model
Unsuitable for naturally ventilated, or mixed mode buildings
Difficult to meet this narrow specification of thermal comfort without HVAC even in relatively mild climatic zones like New Zealand
Within the context of the high energy penalty that is incurred when near isothermal conditions are maintained.

13. Green office spaces
An illustration of indoor environment control dilemma in Green buildings. Energy efficient passive control system on the right-hand side; monotonous mechanical control system on the left-hand side
- Onyeizu, E. Can Architecture increase productivity? The case of green certified buildings. PhD Thesis, University of Auckland

14. Findings: Objective 2 NV are best for New Zealand Climate
In general occupants can work between 18 – 25 degrees
Personal control – occupants interaction with the indoor environment – active not passive occupants
NV have low environmental impact
Less pollution
Less energy usage
NV have lower operation costs
Low maintenance
Less reliance on HVAC

15. Factors affecting NV in New Zealand
Occupant Satisfaction
Limited by the size and layout of the office
Individual offices have higher occupant satisfaction than large open-plan offices
Let in unwanted elements – wind, cold, excess heat, fumes, noise etc.
Design
More complex to design
Consideration of more factors e.g. rise in outdoor temperature, noise, lighting etc.
Required high skills and creativity
Not suitable for high rise buildings – upper-air wind
Cost
More initial cost to reach adequate thermal comfort through passive design

16. Conclusion
NZ Green Star IEQ criteria for thermal comfort do not encourage naturally ventilated office buildings
Perhaps if the NZ Green Star IEQ criteria for thermal comfort can be amended to promote the adaptive model that encourages natural ventilation, more designers could be interested in adopting this model.
experts in this field prefer naturally ventilated office buildings to air conditioned ones.
naturally ventilated office buildings are more complex to design amongst other factors that require consideration.