Presentation by Prof Shaun Fitzgerald – CEO, Breathing Buildings More information: https://storify.com/subutcher/cost-effective-thermal-comfortsolutions-for-the-p

1. shaun.fitzgerald@breathingbuildings.com
T +44 1223 450060
PSBP and Facilities Output Specification
Thermal comfort and indoor air quality in schools

2. BRE/DfES study (2006)
School N Ventilation rates (L/s per person)
< 3 < 8 max min
(%) (%)
West Grove 10 3 (30) 9 (90) 8.7 1.6
Moorside 10 2 (20) 10 (100) 6.5 1.8
Wavendon Gate 9 4 (44) 9 (100) 7.7 1.3
Bramingham 10 9 (90) 9 (90) 12.1 0.5
Baltonsborough 7 4 (57) 6 (85) 20.9 0.9
Gallions 8 4 (50) 7 (87) 8.6 1.3
Bounds Green 10 3 (30) 10 (100) 7.9 0.9
Victoria 8 7 (87) 8 (100) 3.6 0.5
All results 72 35 (49) 67 (93) 20.9 0.5
• 8 Schools examined, all post 1995
• Every classroom had periods with less than 3l/s/person
• In total, 50% of measurements were below 3l/s/person
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3. Energy Use In Buildings
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• Heating bills much higher than
modelling predictions in
naturally ventilated schools
• Carbon targets missed by factor
of 2 or more

4. ©Breathing Buildings Ltd.
Further Challenges

5. ©Breathing Buildings Ltd.
Thermal comfort
• Draughts being defined and
excluded for first time in PSBP
• PSBP based on Operative
temperature
• Lower temperatures of exposed
surfaces contribute to thermal
comfort, and compliance with
regulations

6. ©Breathing Buildings Ltd.
Energy Use
• Mixing of air needed instead of radiators
• Passive cooling requested, with thermal mass and night
ventilation
• Limit use of mechanical cooling to high heat gain areas
• Mechanical ventilation should not be sole method of
summertime ventilation

7. ©Breathing Buildings Ltd.
Draughts Not Allowed
Definition of a cold draught and mitigation strategy
• 2.8.16 c) “In naturally ventilated spaces, the Contractor
shall provide mixing of ventilation air with room air to
avoid cold draughts in the occupied zone during
wintertime. In wintertime the minimum air temperature of
air delivered to the occupied zone at 1.4m above floor
level shall not be more than 5°C below the normal
maintained temperature”
• 2.8.21 l) “The Contractor shall ensure that the School is
designed so that the air speed flowing across occupants in
winter is <0.3 m/s in all teaching spaces”

8. ©Breathing Buildings Ltd.
Summertime
• New way of thinking about thermal comfort in summer
Running mean of recent maximum external temperatures
Operative temperature
• New overheating criteria
Criterion 1 – Hours of Exceedance
Criterion 2 – Daily Weighted Exceedance
Criterion 3 – Upper Limit Temperature

9. ©Breathing Buildings Ltd.
Summertime Overheating
2.8.17 e) Simulation tool needs to calculate Operative Temperature, Top and
Running Mean Temperature, Trm . Calculations should realistically account for
occupancy pattern of the building and the adaptive behaviour of the building
occupants
Tmax = 0.33Trm + 21.8 (normal operation)
Overheating criteria assessed in terms of predicted operative temperature
Top relative to Tmax
DT = Top - Tmax

10. ©Breathing Buildings Ltd.
Summertime Overheating
• Criterion 1 – Hours of Exceedance
For schools, the number of hours (He) that ΔT is greater than or equal to
one degree (K) during the period May to September inclusive shall not be
more than 40 hours
Rationale: How often a building is likely to exceed its
comfort range during summer months is a useful
metric

11. ©Breathing Buildings Ltd.
Summertime Overheating
• Criterion 2 – Daily Weighted Exceedance
To allow for the severity of overheating the weighted exceedance (We) shall be less
than or equal to 6 in any one day
where We = Σhe x wf = (he0 x 0) +(he1 x 1) +(he2 x 2) +(he3 x 3)
Where the weighting factor wf = 0 if ΔT ≤ 0, otherwise wf = Δ T,
and hey = time in hours when wf=y !!!!
Number of hours a day above the allowable maximum temperature multiplied by
amount above this
Rationale: Acceptable severity level of overheating on a day

12. ©Breathing Buildings Ltd.
Summertime Overheating
• Criterion 3 – Upper Limit Temperature
To set an absolute maximum value for the indoor operative temperature
the value of ΔT shall not exceed 4K
Rationale: Sets limit beyond which normal adaptive
actions will be insufficient to restore personal comfort

13. ©Breathing Buildings Ltd.
Performance In Use
• “Average internal temperature must not
exceed average external air temperature
by more than 5°C”

14. ©Breathing Buildings Ltd.
Thermal Mass

15. ©Breathing Buildings Ltd.
Thermal Mass
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