Transcript Slide 1

CAN INDOOR AIR QUALITY IN VICTORIAN CLASSROOMS
SATISFY BB101 REQUIREMENTS?
NAFSIKA C.C. DROSOU
[email protected]
School of Civil and Building Engineering Loughborough University, LE11 3TU, UK
RESULTS & DISCUSSION
ABSTRACT
METHODOLOGY
Research indicates that high Carbon Dioxide (CO2) levels in classrooms
adversely affect health and productivity of students. Building Bulletin 101
(BB101) provides Indoor Air Quality (IAQ) requirements and optimum CO2
concentrations for classrooms. This study aims to determine the most
feasible and effective window intervention for a naturally ventilated
Victorian classroom to achieve BB101 stipulated CO2 levels. Defining the
current ventilation strategy performance of the space is achieved by
collecting and analysing monitoring, interview and observation data. The
suitability of a number of structural and window opening system
interventions is primarily checked against maintenance, ease of use,
acoustics and safety. Fit interventions are then simulated, as parametric
Computational Fluid Dynamic (CFD) studies, in order to quantify the
impact of their ventilation performance in terms of CO2 concentration,
ventilation rate and thermal comfort parameters, such as draught and
vertical temperature gradient. Conclusions are drawn and compared to
the intervention proposed by a parallel piece of research on the same
monitoring data concerning energy use and IAQ improvement.
CASE STUDY
A Victorian classroom in a Leicestershire primary school located in a
village of the East Midlands in the UK.
ANALYSIS
CONCLUSIONS
CHECKING FOR CONVERGENCE OF THE CFD SOLUTION
CFD RESULTS VS REALITY
How base case results match monitoring, interview and observation data:
CO2 concentration is lower in the base case by 5-15%
Internal temperature is higher in the base case by 20-25%
This discrepancy will affect the validity of the forthcoming simulation results
for each of the interventions modelled.
BASE CASE
CO2 concentration at 1m (children’s seated head height) and at the
classroom’s cross section with 0.001518 = 1000ppm as max value:
Average CO2 is 0.001828kg/kg = 1203.57ppm
which as expected is > BB101 requirement (1000ppm)
and matches monitored & observed data
MONITORING
External and internal temperature (°C), as well as CO2 concentration
levels (ppm by volume)
LIMITATIONS
- Cleaners turning sensors (power) off
- Limited data storage capacity of sensors needs frequent site visits for
short interval monitoring periods (here 3min & 5min)
- Confusing intelligent heating system that no one in the school seems to
know how to operate because of lack of training and communication
- Travel costs found to inhibit frequent visits by the system maintenance
company, leaving the building manager helpless.
CFD simulation
- Difficulty in following exact actual measurements, dimensions & distances
due to simplifications that keep the xx’, yy’, zz’ mesh at low number of
cells
- PHOENICS although not complex compared to the physics of fluid
dynamics has a complicated user manual with limited examples that
concern indoor environments
INTRODUCTION
School buildings account for 15% of the total CO2 emissions of
commercial and public buildings [1]
Inadequate ventilation is found to cause over 50% of IAQ related
problems.
FUTURE WORK & RECCOMENDATIONS
The results to are to be supplemented with those of the whole number of
interventions (8) modelled dynamically in IES during a parallel study of the
same classroom on the heating energy cost of the same interventions.
In green are the CO2 values equal to
0.001911kg/kg = 1258.22ppm taking
up the volume of air from about
0.6-1.5m high
WALKTHROUGH & 2 COVERT WINDOW OBSERVATION DAYS
Collection of dimensions & physical measurements
Source: National Institute of Occupational Safety and Health
With budgets for school projects being slashed it would be interesting to
investigate the effect on CO2 concentration and IAQ of cheaper retrofit
solutions the Local Authorities turn to.
Indoor CO2 measurements are a good indicator of IAQ and ventilation is
viewed as the most effective means of restoring IAQ to an acceptable
level [2]
BB101 provides the framework for ventilation in schools [3].
- For CO2 used as the indicator for IAQ:
Maximum CO2 concentration: 5000ppm during the teaching day
Mean CO2 concentration: kept below 1500ppm at any occupied time,
with capacity for space occupants to lower it to 1000ppm (measured at
seated head height)
- Specifically for ventilation rates of natural ventilation systems:
Minimum: 3 l/s per person
Minimum daily average: 5 l/s per person
with capability for purge ventilation of 8 l/s per person
Vertical temperature variation (at 0.1m and 1m)
The difference between feet and head temperature is found to be over 7°C
this would have over 50% of occupants feeling
dissatisfied with thermal comfort.
the high temperature is in accordance with the students’
complaints of the class being too hot.
INTERVIEWS
Of the teacher, maintenance personnel, students and school Eco-Team
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5
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ACKNOLEDGEMENTS
Thermal comfort is checked against ASHRAE standards [4] for vertical
temperature variation and draught.
CFD MODELLING (using FLAIR in PHOENICS)
For the base case:construct geometry, define boundary conditions, select
turbulence model, perform grid independence test. Model interventions
This study is based on previous work of Kate Simpson [5] on IAQ of the
same school which found the particular classroom not meeting the BB101
requirements throughout the teaching day.
Draught risk (at 0.1m and 1m)
Draught is kept at low levels bellow 0.2m/s
increasing the feeling of heat
London Loughborough Centre
for doctoral research
in energy demand
[1] DCSF (2009). Towards a Schools Carbon Management Plan.
Department of Children Schools and Families, London: The Stationery
Office
[2] Sundell, J. (2004) 'On the History of Indoor Air Quality and Health', in
Indoor Air, 14(7): pp. 51–58
[3] DfE (2006). Building Bulletin 101: Ventilation of School Buildings.
Department for Education.
[4] ASHRAE (2009). 2009 ASHRAE Handbook - Fundamentals. Atlanta,
GA: American Society of Heating, Refrigerating and Air-Conditioning
Engineers. Chapter 9
[5] Simpson, K. (2011). The Indoor Air Quality of a Victorian Primary
School with a post 1968 Extension. MRes Thesis: Loughborough
University
This project is supervised by Prof. Malcolm Cook and Prof. Darren Wolf,
funded by the London-Loughborough Doctoral Training Centre in Energy
Central House
Demand and supported by the Civil & Building Engineering Department of
14 Upper Woburn Place
Loughborough University.
London, WC1H 0NN