natural ventilation and low energy building design

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T 01223 450060

F 01223 450061

Natural ventilation and low

energy building design

©Breathing Buildings

Energy Use In Buildings

Typ

ical

Source: Baker and Steemers

full

AC

Significant HVAC equipment

Energy consumption - heating and cooling run

simultaneously

Mechanical Ventilation Scheme


1st Floor Sunbury A, Week 16/11 through 21/11

0

300

200

100

Height (cm)

17 23 21 19

Temperature (C)

24 22 20 18

Starts at 0600 Sat 16/11, finish 1050 on Thur 21/11

25 26 #1 near the end is mauve

#2 mid-way between 1 and 4 is green

#3 Stand near window, ¼ way along the building is red

# 4 stand near the middle and away from the window is blue

#5 near the middle, but at the window is black


Mechanical Ventilation Scheme

Hot air driven out at top

Cold air driven

in at base

Neutral point – no

flow (in absence of

wind)

Pressure

Heig

ht

Exterior air Interior air

Displacement


Displacement

Hot air driven out at top

Cold air driven

in at base

Inflow

Pressure

Heig

ht

Exterior air Interior air



Simple Spaces

HOUGHTON HALL

HOUGHTON HALL CONSERVATION AREA

ADJOINING BUSINESS PARK PLOT

HOUGHTON HALL


HOUGHTON HALL

PASSIVE VENTILATION AND SOLAR CONTROL TECHNIQUES

Trickle vents

Concrete soffits



Which way does the air flow?

Complex Spaces


Complex Spaces – Houghton Hall


Water-bath Modelling


Air enters through 1st floor vents

cool interior

Uniform initial conditions (20oC)

Air exits through 1st floor vents

Hot 1st floor

1st floor initially hotter than ground

Multiple modes can be obtained with numerical modelling … but

• You need to know what you are looking for!

• Time consuming!

CFD Modelling

Atrium peak

temperatures follow

exposure to sun

Region near/within

atrium hotter than desk

area under exposed

concrete benefit of

thermal mass

First floor 3-21 July 2003

10

15

20

25

30

35

40

13-Jul 13-Jul 14-Jul 14-Jul 15-Jul 15-Jul 16-Jul

Time

Te

mp

era

ture

/C

ext temp

H 144

H 145

H 640788

H 642426

H146

H 147

H 148

• North side of

the atrium

• East end of the

atrium

• South side of

the atrium

• West end of the

atrium (dark

blue line, very

small peak)

• Within main

floor

1st floor


Temperature Measurements

3-21 July Average temperatures

5

10

15

20

25

30

35

40

3-Jul 8-Jul 13-Jul 18-Jul

Time

Te

mp

era

ture

/C ext temp

GF

FF SS

FF NS

SF

Main floor

temperatures less

than outside and

buffered by

thermal mass…

but still rather

warm mid-July



23July-14Aug average temperatures

5

10

15

20

25

30

35

40

23-Jul 28-Jul 2-Aug 7-Aug 12-Aug

Time

Te

mp

era

ture

/C outside

GF

FF SS

FF NS

SF

Warm inside

again in early

August



15Aug-10Sept Average temperatures

5

10

15

20

25

30

35

40

15-Aug 20-Aug 25-Aug 30-Aug 4-Sep 9-Sep

Time

Te

mp

era

ture

/C

outside

GF

FF SS

FF NS

SF

Cooler after

mid-August



23July-14Aug average temperatures

5

10

15

20

25

30

35

40

23-Jul 28-Jul 2-Aug 7-Aug 12-Aug

Time

Te

mp

era

ture

/C outside

GF

FF SS

FF NS

SF

Can we improve performance?


-3

-2

-1

0

1

2

3

4

5

6

28-Jun 18-Jul 07-Aug 27-Aug 16-Sep

Date

Tim

e l

ag (

hr)

tmin lag

tmax lag

Range of time lag for building to reach max or min temp


Time Lags

Buffer for max temp 1-3 hours

August-Sep 2003

0

2

4

6

8

10

12

14

<0 0 to 1 1 to 2 2 to 3 3 to 4 >4

Delay (hrs)

Fre

qu

en

cy

Grd S

1st S

1st N

2nd N



Maximising Effectiveness of Thermal Mass

0

5

10

15

20

25

30

35

40

0 10 20 30 40 50 60 70

tem

pe

ratu

re (

C)

time (hrs)

Toutside

Tconcrete

T air internal

T perceived

thermal mass calc.xls

•Hot and still day

(06/08/03)

•Fans are operating all day

•All windows

open

Air Flow Results


0

10

20

30

40

50

60

Houghton Hall Required

Air

su

pp

ly (

l/sp

p)

43-60

8

Measurements show fresh air supply well in excess of minimum

required

Air Quality

5

10

15

20

25

30

35

40

45

0:00 4:00 8:00 12:00 16:00 20:00 0:00Time

Tem

peratu

re/C

Upper part of

atrium (2nd floor)

outside Second

floor

•Limited

number of

trickle vents

open


Night Time Operation

July outside air temperature.

5

10

15

20

25

30

35

40

28-Jun 3-Jul 8-Jul 13-Jul 18-Jul 23-Jul 28-Jul 2-Aug 7-Aug

August outside temperature.

5

10

15

20

25

30

35

40

45

28-Jul 2-Aug 7-Aug 12-Aug 17-Aug 22-Aug 27-Aug 1-Sep 6-Sep

1. Opportunity to use cool air from outside during night

even more effectively to reduce building temperature

2. Reduce window openings during summer day to

maximise benefit of thermal mass

Opportunity for Improvement


Contact Theatre, after renovation

0

5

10

15

20

25

30

9/5/04

0:00

9/5/04

12:00

9/6/04

0:00

9/6/04

12:00

9/7/04

0:00

9/7/04

12:00

9/8/04

0:00

9/8/04

12:00

9/9/04

0:00

9/9/04

12:00

9/10/04

0:00

time

Te

mp

era

ture

(C

) Stack 1

Stack 2

Stack 3

Stack 4

external

top of theatre

Stack 3 inflow? Stack 2 also inflow later?

Contact Theatre, Studio

Evening/

Morning

Warmer

inside

than

outside


-130 0 20 130

125

0

-150

-300T

X

Y

Stack 1

19-20

18-19

17-18

16-17

15-16

14-15

-130 0 20 130

125

0

-150

-300T

X

Y

Stack 2

19-20

18-19

17-18

16-17

15-16

14-15

-130 0 20 130

125

0

-150

-300T

X

Y

Stack 3

19-20

18-19

17-18

16-17

15-16

14-15

-130 0 20 130

125

0

-150

-300T

X

Y

Stack 4

19-20

18-19

17-18

16-17

15-16

14-15

Stack 3 inflow balance of base and stack areas ©Breathing Buildings

0

5

10

15

20

25

30

9/10/04

0:00

9/10/04

12:00

9/11/04

0:00

9/11/04

12:00

9/12/04

0:00

9/12/04

12:00

9/13/04

0:00

9/13/04

12:00

9/14/04

0:00

9/14/04

12:00

9/15/04

0:00

time

Te

mp

era

ture

(C

) Stack 1

Stack 2

Stack 3

Stack 4

external

top of theatre

Mid-points of stacks 1 + 4 cooler than stacks 2 + 3 ©Breathing Buildings

-130 0 20 130

125

0

-150

-300 20-21

19-20

18-19

17-18

16-17

-130 0 20 130

125

0

-150

-300

Stack 2

-130 0 20 130

125

0

-150

-300

X

Stack 3

Stack 1

-130 0 20 130

125

0

-150

-300

Temperature

Stack 4

Counterflow in stacks 1 + 4

Contact Theatre, Studio

6.5m

5m

Mixing ventilation in practice when warmer inside and

stack area >> base vent area



Conventional Natural Ventilation

©Breathing Buildings Ltd.

Winter – Upwards displacement ventilation

Not to be distributed to 3rd parties


Recommended Winter Strategy


Winter – Mixing ventilation



Recommended Summer Strategy


Summer – Upwards displacement ventilation


East Malling School, Kent


Pilgrim School, Kent


Exact interface can be adjusted for each project as required by the client

Control Interface



Atrium Design



Port Regis School, Dorset



Monkseaton School, Newcastle


©Breathing Buildings ©Breathing Buildings Ltd.

QAC, Birmingham

Energy Savings

020406080

100120140160

Fossil Fuels Energy Consumption kWh/m2/yr

Port Regis School

* CIBSE Guide F Table 20.1 Fossil fuel use in secondary schools ** Total energy consumption of building


Internal Climate


Belvoir High School 0 hours for which Troom>28oC (Troom) max = 27.5oC (Troom – Texternal)max = 2.3oC

BB101 Standards 120 hours for which Troom>28oC (Troom) max = 32oC (Troom – Texternal)max = 5oC

The daily average CO2 never exceeds 1500ppm


Internal Comfort


Before

After Harston Primary School


Internal Comfort



Summary


• Natural ventilation low energy

• Design parameters – Vent area

– Head

– Thermal mass

– Wind

• Control strategy – Mixing Winter

– Displacement Summer

natural ventilation and low energy building design

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