Natural ventilation and low energy building design
Transcript of Natural ventilation and low energy building design
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©Breathing Buildings
Energy Use In Buildings
Typ
ical
Source: Baker and Steemers
full
AC
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Significant HVAC equipment
Energy consumption - heating and cooling run
simultaneously
Mechanical Ventilation Scheme
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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
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Mechanical Ventilation Scheme
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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
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Displacement
Hot air driven out at top
Cold air driven
in at base
Inflow
Pressure
Heig
ht
Exterior air Interior air
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Simple Spaces
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HOUGHTON HALL
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HOUGHTON HALL CONSERVATION AREA
ADJOINING BUSINESS PARK PLOT
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HOUGHTON HALL
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HOUGHTON HALL
PASSIVE VENTILATION AND SOLAR CONTROL TECHNIQUES
Trickle vents
Concrete soffits
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Which way does the air flow?
Complex Spaces
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Complex Spaces – Houghton Hall
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Water-bath Modelling
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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
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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
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Temperature Measurements
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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
Temperature Measurements
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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
Temperature Measurements
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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
Temperature Measurements
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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?
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-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
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Time Lags
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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
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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
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•Hot and still day
(06/08/03)
•Fans are operating all day
•All windows
open
Air Flow Results
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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
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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
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Night Time Operation
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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
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Contact Theatre, after renovation
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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
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-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
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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
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-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
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Contact Theatre, Studio
6.5m
5m
Mixing ventilation in practice when warmer inside and
stack area >> base vent area
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Conventional Natural Ventilation
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Winter – Upwards displacement ventilation
Not to be distributed to 3rd parties
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Recommended Winter Strategy
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Winter – Mixing ventilation
Not to be distributed to 3rd parties
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Recommended Summer Strategy
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Summer – Upwards displacement ventilation
Not to be distributed to 3rd parties
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Night Cooling
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QAC, Birmingham
Not to be distributed to 3rd parties
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East Malling School, Kent
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Pilgrim School, Kent
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Exact interface can be adjusted for each project as required by the client
Control Interface
Not to be distributed to 3rd parties
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Atrium Design
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Port Regis School, Dorset
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Monkseaton School, Newcastle
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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
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Internal Climate
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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
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Internal Comfort
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Before
After Harston Primary School
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Internal Comfort
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Summary
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• Natural ventilation low energy
• Design parameters – Vent area
– Head
– Thermal mass
– Wind
• Control strategy – Mixing Winter
– Displacement Summer