School Venta.docx

7/28/2019 School Venta.docx

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The Development of Regulatory ComplianceTools for Ventilation and Overheating in Schools

IBPSA 29th July

John Palmer Chairman CIBSE Schools Design GroupMalcolm Orme

Willy Pane


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Design Criteria

he appropriate design conditions for ventilation and

summertime thermal comfort in schools in England andWales are given in Building Bulletins published by theDepartment for Children Schools and Families:

Building Bulletin 101 Ventilation in School Buildings

available from www.teachernet.gov.uk


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Building Bulletin 101 states that

When measured at seated head height, during the continuous periodbetween the start and finish of teaching on any day, the averageconcentration 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 theconcentration of carbon dioxide to 1000 ppm.

The maximum concentration of carbon dioxide

should not exceed 5000 ppm during the teachingday.

Advisory Performance Standards


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Thermal Comfort in SummerBuilding Bulletin 101 states that:

The performance standards for summertime overheating incompliance with Approved Document L2 for teaching andlearning areas are:

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

b) The average internal to external temperature

difference should not exceed 5C (i.e. the internal

air temperature should be no more than 5C above

the external air temperature on average)

c) The internal air temperature when the space is

occupied should not exceed 32C.


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Design Tools Developed for Department of ChildrenSchools and Families

ClassVent ClassCool

available from www.teachernet.gov.uk


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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 op ening) 4

Openable part of the window

ClassRoom Occupancy

Number of Pupils 30

Building Height Teacher (1 or 2?) 2

Floor Area = 58

Internal Volume = 232 Design and Envir omental Variables

Number of ppl 32 Temperature Profile - default season or us er input 0

Flow Requirements m/sec 0.384 Default temperatures Outside Inside

Flow Requirements ach 5.958621 1 Winter 5 20

Floor (input 0 for Ground Floor) 0 2 MidSeason 11 203 Summer 24 27

4 Other - User defined t emperatures 1 28

Extra Height for Sloping Ceilings - m 0

(leave it as 0 for horizontal ceilings) Go to any strategy by clickingSingle Vent Here

Twin Vents Here

Vent & Window Here

Low Level Vent CrossFlow Here

Fixed part of the Window Stack Here

Door to corridor (seen through window) Stack (multiple rooms) Here

High Level Vent, leading into corridor or Stack

Required Volume flowThis spreadsheet is a simple tool to predict th e area of the openings needed to provide external air under specifi ed condition s

The recommended values are: 3, 5 or 8 li tres/second/person

The User should enter the geometry and occupancy for the room and then prog ress throug ht the various design scenarios as indi cated on the tabs below

Six possible combi nations are given that include variations of Singl e Sided, Crossflow and Stack ventilation .

The "Single Vent" is either a single opening like a window o r a vent; the "Twin Vent" has tw o (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 condi tions f or each period of t he year are as shown in t he table above

Note: the areas predict ed 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 pro vides this effective area will be greater than these calculations impl y.

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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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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,

litres/sec/perso

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

M

W

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, m

F

low,

litres/second/pe

rson

Design Strategy

Cross Flow, two openings of equal areas

Single Sided, one opening

Single Sided, low and high level openings of equal area

Opening with stack

Areas of front facade openings for dif ferent strategies

W M S

Cross Flow, two openings 0.75x2 0.97x2 1.72x2Single Sided, one opening 1.5 1.9 3.4

Single Sided equal opening 0.39 0.53 1.09

Opening with stack 0.21 0.28 0.62

Stack outlet and inlet from room 1.0

M

S = area provided for summer design condition

M = area provided for midseason design condition

W = area provided for winter design condition

S

W


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Developing ClassCool

Dynamic simulation - hourly data, overheating is a short termeffect

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 J une 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 : 13

o 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 classroomblocks, 2 storeys high, angled at 45 to each other.

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

The four different blocks allowed the 8 basic orientations to bemodelled simultaneously

The simulation used the London TRY (Test Reference Year)

weather file and the model is located in Heathrow for solar shadingcalculations.


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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 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


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Thank you for your attention

School Venta.docx

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