Ventilation in schools - CIBSE School ... - cibse-sdg. · PDF fileThe Development of Regulatory Compliance Tools for Ventilation and Overheating in Schools IBPSA 29 th . July. John

The Development of Regulatory Compliance Tools for Ventilation and Overheating in Schools

IBPSA 29th July

John Palmer – Chairman CIBSE Schools Design Group

Malcolm Orme

Willy Pane

IBPSA 29th July

Design Criteria

The appropriate design conditions for ventilation and summertime thermal comfort in schools in England and Wales are given in Building Bulletins published by the Department for Children Schools and Families:

Building Bulletin 101 – Ventilation in School Buildings

available from www.teachernet.gov.uk

IBPSA 29th July

Building Bulletin 101 states that

“When measured at seated head height, during the continuous period between the start and finish of teaching on any day, the average concentration of carbon dioxide should not exceed 1500 parts per million (ppm)”

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At any occupied time, including teaching, the occupants should be able to lower the concentration of carbon dioxide to 1000 ppm.

The maximum concentration of carbon dioxide should not exceed 5000 ppm during the teaching day.

Advisory Performance Standards

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Thermal Comfort in SummerBuilding Bulletin 101 states that:

“The performance standards for summertime overheating in compliance with Approved Document L2 for teaching and learning areas are:

a) There should be no more than 120 hours when the air temperature in the classroom rises above 28°C,

b) The average internal to external temperature difference should not exceed 5°C (i.e. the internal air temperature should be no more than 5°C above the external air temperature on average)

c) The internal air temperature when the space is occupied should not exceed 32°C”.

Design Tools Developed for Department of Children Schools and Families

ClassVent

ClassCool

available from www.teachernet.gov.uk

IBPSA 29th July

This Spreadsheet produces the area of ventilation openings Standard ClassRoom Geometry and Occupancy

required for the supply of a specific volume flow per personClassRoom Geometry

Legend of typical ventilation elements Width - m 7.25Depth - m 8

High Level Vent Height - m (ceiling height or highest level for opening) 4Openable part of the window

ClassRoom OccupancyNumber of Pupils 30

Building Height Teacher (1 or 2?) 2Floor Area = 58Internal Volume = 232 Design and Enviromental Variables Number of ppl 32 Temperature Profile - default season or user input 0Flow Requirements m/sec 0.384 Default temperatures Outside InsideFlow Requirements ach 5.958621 1 Winter 5 20Floor (input 0 for Ground Floor) 0 2 MidSeason 11 20

3 Summer 24 274 Other - User defined temperatures 1 28

Extra Height for Sloping Ceilings - m 0(leave it as 0 for horizontal ceilings) Go to any strategy by clicking

Single Vent HereTwin Vents HereVent & Window Here

Low Level Vent CrossFlow HereFixed part of the Window Stack HereDoor to corridor (seen through window) Stack (multiple rooms) HereHigh Level Vent, leading into corridor or Stack

Required Volume flowThis spreadsheet is a simple tool to predict the area of the openings needed to provide external air under specified conditionsThe recommended values are: 3, 5 or 8 litres/second/personThe User should enter the geometry and occupancy for the room and then progress throught the various design scenarios as indicated on the tabs below Six possible combinations are given that include variations of Single Sided, Crossflow and Stack ventilation.The "Single Vent" is either a single opening like a window or a vent; the "Twin Vent" has two (identical) vents at different heights.The "Vent Window", allows the user to change the window area (which will then produce a different area for the inlet vent).The "CrossFlow" and "Stack(single)" and "Stack(multiple)" ventilation cases allow further inputs for windspeed and up to 3 floors in the stack cases.

The temperatures recommended as the default conditions for each period of the year are as shown in the table aboveNote: the areas predicted are effective areas - i.e. they will pass the same volume of air as a square edged orifice of the same area.The "hole in the wall" to install an actual ventilator that provides this effective area will be greater than these calculations imply.

1 28

User

12 l/sec/per

ClassVent - Natural Ventilation Design & Part F Compliance Tool

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Based on CIBSE AM10

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Single sided – single opening

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Results

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Other Design Options

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Predicted Annual Performance

Single Side Ventilation, 2 equal openings at low and high level, areas sized according to season; London TRY with wind

0

8

16

24

Mon,01/Jan

Tue,20/Mar

Wed,06/Jun

Thu,23/Aug

Fri,09/Nov

Occupied time on 12 month (no summer hols)

Flow

, litr

es/s

ec/p

erso

n

Outdoor air inflow for opening sized for Summer

Outdoor air inflow for opening sized for Winter

Outdoor air inflow for opening sized for midSeason

Winter Period Winter PeriodmidSeason midSeasonSummer

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Predicted Annual PerformanceOutdoor air supply rate for different strategies; London TRY, with wind.

Openings sized according to season

W

M

S

MW

S

W

M

S

0

8

16

24

32

0 0.5 1 1.5 2 2.5 3 3.5 4Area of front facade opening, m²

Flow

, litr

es/s

econ

d/pe

rson

Design StrategyCross Flow, two openings of equal areasSingle Sided, one openingSingle Sided, low and high level openings of equal areaOpening with stack

Areas of front facade openings for different strategies W M SCross Flow, two openings 0.75x2 0.97x2 1.72x2 Single Sided, one opening 1.5 1.9 3.4Single Sided equal opening 0.39 0.53 1.09Opening with stack 0.21 0.28 0.62Stack outlet and inlet from room 1.0

M

S = area provided for summer design conditionM = area provided for midseason design conditionW = area provided for winter design condition

S

W

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Classroom DefinitionThe basic classroom is assumed to have a floor area of ~54m² and a volume of ~162m³. This tool does not allow a change in these variables, as it cannot replace proper thermal modelling.

Note to the user:- do not cut 'n' paste cells unless using /edit/value which will preserve the formatting of the cells.Gf 1F Ratios Natural

Window Area Percentage of Façade Area ( between 20% and 60%) 60 60 6060

g-value Choose between No, Partial, Full solar control (between 0.675 and 0.38 ) 0.679if choosing "Other", provide input from Glazing datasheets here ===>> 0.668 and here> 0.668 0.668 0.668

Louvres Numbers of louvre blades, 0 to 6 -1

Classroom Selection by orientation and floorGf Max 1F Orientation Gf 1F

Overhang Width in cm, North East (120cm for 100% shading of a 185cm window) 0 120 0 North East 0Width in cm, East (169cm for 100% shading of a 185cm window) 0 169 169 East 0Width in cm, South East (120cm for 100% shading of a 185cm window) 120 120 60 South East 100Width in cm, South (98cm for 100% shading of a 185cm window) 98 98 98 South 100Width in cm, South West (120cm for 100% shading of a 185cm window) 120 120 60 South West 100Width in cm, West (169cm for 100% shading of a 185cm window) 169 169 84.5 West 100Width in cm, North West (120cm for 100% shading of a 185cm window) 120 120 60 North West 100Width in cm, North (98cm for 100% shading of a 185cm window) 98 98 49 North 100

MidPane Blinds Shading Coefficient : - Choose "Full", "Half", "None", or "Other" 0.64

If choosing "Other", provide input in here ===================>> 0.878 and here> 0.878 0.878 0.878

Casual Gains Between 15 W/m² and 115 W/m² 115 115 115

Thermal Mass Low (1.18 W/K/m²), Medium (3.0 W/K/m²), High (4.9 W/K/m²), (GF). 2If choosing "Other", provide input in here ===================>> 4 4 4

4Day Ventilation Day Ventilation, l/sec/person - between 5 l/sec/pers and 13 l/sec/pers 8 8 8 8 8

8Night Ventilation Night Ventilation 0 to 512 l/sec ( ~12 ach) 0

Input the flow in l/sec here =======> 0 111 Volume = 161.7 0

Class AREA = 53.9Conditional Formatting statemen Results Orientation Gf 1f Gf 1f Gf 1fTRUE TRUE Hours of Overheating above 28°C (figures rounded up to the next 5 h) North East 410 315 9.9 7.4 >35°C >35°CTRUE TRUE Hours of Overheating above 28°C (figures rounded up to the next 5 h) East 415 270 10.4 6.6 >35°C >35°CTRUE TRUE Hours of Overheating above 28°C (figures rounded up to the next 5 h) South East 305 295 8.6 7.4 >35°C >35°CTRUE TRUE Hours of Overheating above 28°C (figures rounded up to the next 5 h) South 290 265 8.1 6.3 >35°C >35°CTRUE TRUE Hours of Overheating above 28°C (figures rounded up to the next 5 h) South West 300 300 8.5 7.3 >35°C >35°CTRUE TRUE Hours of Overheating above 28°C (figures rounded up to the next 5 h) West 330 295 8.6 7.6 >35°C >35°CTRUE TRUE Hours of Overheating above 28°C (figures rounded up to the next 5 h) North West 340 315 8.6 7.1 >35°C >35°CTRUE TRUE Hours of Overheating above 28°C (figures rounded up to the next 5 h) North 335 310 8.5 6.9 >35°C >35°C

Hours >28°C Max TintAvg Delta T

Half

0

Middle Weight

No Solar Control

in l/sec

Partial Solar Control

0

Half

Middle Weight

in l/sec

Window Area

g-value

Louvres

Classroom Selectio

Overhang

MidPane Blinds

Casual Gains

Thermal Mass

Day Ventilation

Night Ventilation

Classroom Selection by orientation and floor

53.9Orientation Gf 1f Gf 1f Gf 1fNorth East 255 265 6.9 6.3 >35°C >35°C

East 230 250 7.3 5.9 >35°C 34.5South East 230 260 6.7 6.3 34.7 35.0

South 215 250 6.3 5.7 34.4 34.5South West 230 255 6.4 6.3 34.6 34.6

West 245 255 6.5 6.6 34.4 34.3North West 250 280 6.5 6.2 34.9 34.4

North 240 275 6.4 6.1 34.8 >35°C

Hours >28°C Max TintAvg Delta T

ClassCool – Avoiding Overheating Part L Compliance Tool for Classrooms

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Developing ClassCool

Dynamic simulation - hourly data, overheating is a short term effect

IES Apache V5.01

Experimental design

response surface methodology

second order face centred hyper-cubic design

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Analysis Steps – Parameter Selection

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Parameter ranges -- low : mid-point : high

Step One – Solar Gains• glazed area (%) 20 : 40 : 60• normal g-value 0.68 : 0.52 : 0.38• overhangs (% shading) 0 : 50 : 100 (shading on June 21st)• louvres 0 : 3 : 6 (shading by SUNCAST)• blinds 1 : 0.64 : 0.28 (shading coefficient)

Step Two – overheating prediction• solar gains from step one• admittance (W/K/m2) 1.1 : 3.0 : 4.9• Ventilation

o Day (l/s per person) 5 : 8 : 13o Night (air changes/h) 0 : 4 : 12

• casual gains (W/m2) 15 : 65 : 115 (also scheduled by occupancy)

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The simulated model (seen above) is made of 4 classroom blocks, 2 storeys high, angled at 45° to each other.

Each floor has 3 classrooms with a different amount of glazed area, a corridor and three other classrooms on the opposite side

The four different blocks allowed the 8 basic orientations to be modelled simultaneously

The simulation used the London TRY (Test Reference Year) weather file and the model is located in Heathrow for solar shading calculations.

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Predicted Performance

Internal air temperature

Maximum air temperature

Internal to external temperature difference

CIBSE London Test Reference Year

Monday to Friday from 1st May to 30th September

Occupied hours from 9.00am to 3.30pm.

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Example of prediction of solar gains from modeled data

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Solar Gains with Overhang and Shading Coefficient

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Equations behind ClassCool – hours above 28oC

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Equations behind ClassCool – temperature difference

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ClassCool – Thermal Mass Tool

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ClassCool – Casual Gains Tool

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ClassCool – Glazing ‘g-value’ Tool

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Summary

Two simple spreadsheet strategic design tools

Easy to use

Downloadable

Based on full dynamic thermal and coupled modeling

Adopted as Regulation Compliance Tools

IBPSA 29th July

Thank you for your attention