The Future Envelope 12 Interreg IT-AU FACEcamp project ------------ Conference on Building Envelopes 20-21 May 2019, NOI Techpark, Bolzano (Italy) "It’s all about performances".

1. The Future Envelope 12
It’s all about performances
How flow can you go?
Prof Darren Woolf
Hoare Lea / Loughborough University
www.interreg.net
FACEcamp final event | Bolzano, 20-21 May 2019
FACEcamp is funded by European Regional Development Fund and Interreg V-A Italy-Austria 2014-2020.

2. Contents
Ventilation flow:
• Case study 1: Simulating wind pressures (driving force for air flow
through façade)
• Case study 2: Calculating pressure losses (effective areas &
discharge coefficients) and resulting flow through façade openings
Heat flow:
• Case study 3: Heat flow through complex glazing systems
• Case study 4: Impact of glass temperature on room air flow
• Case study 5: Heat transfer with multiple phases (solid, air, water)
and condensation risk
The Future Envelope 12 final event 20-21 May 2019, Bolzano

3. Case study 1: Local wind pressure at a crack or opening
The Future Envelope 12 final event 20-21 May 2019, Bolzano
Wind flow
around
buildings is
very complex.
‘Steady-state’
CFD calculation
(no gusts,
averaged flow).

4. Case study 1: Local wind pressure at a crack or opening
The Future Envelope 12 final event 20-21 May 2019, Bolzano
Pressure on horizontal plane 20m above ground level
Positive and
negative
pressures with
different
magnitudes on
different areas
of façade.
One connected
pressure-flow
system.

5. Case study 1: Local wind pressure at a crack or opening
The Future Envelope 12 final event 20-21 May 2019, Bolzano
Natural ventilation
flow highly dependent
on pressure
differential between
connected openings
(e.g. across an
apartment from one
window to another).

6. The Future Envelope 12 final event 20-21 May 2019, Bolzano
Case study 1: Local wind pressure at a crack or opening
Dynamic thermal model
Positive
pressure
predicted
Uniform
horizontally
Negative
pressure
predicted
(sheltered)
Non-uniform
horizontally
CFD model
WINDWARD FAÇADE:

7. The Future Envelope 12 final event 20-21 May 2019, Bolzano
Case study 1: Local wind pressure at a crack or opening
LEEWARD FAÇADE:
Dynamic thermal model
Negative
pressure
predicted
CFD model
Positive
pressure
predicted

8. The Future Envelope 12 final event 20-21 May 2019, Bolzano
Case study 1: Local wind pressure at a crack or opening
Dynamic thermal model
settings for wind pressure
coefficient:
• Building type
• Exposure
• Height up facade
Apartment results:
Compliance test for overheating
risk in living room / kitchen
changed from ‘marginal fail’ to
‘pass’ using CFD-based wind
pressure coefficients.
Both bedrooms also improved.

9. Top-hung
The Future Envelope 12 final event 20-21 May 2019, Bolzano
Side-hung
Discharge coefficient and effective area
Bottom-hung
Free areaDischarge coefficient (Cd)
Pressure loss e.g.
due to turbulence
Effective area is NOT
a width x height)
Jones and Cook: A review of ventilation opening area
terminology, Energy and Buildings, March 2016
‘An effective area, defined as the product of its discharge
coefficient and its free area, is proposed as a standard
description because it is unambiguous and its measurement
is governed by recognised standards.’
[Also ‘new’ CIBSE AM10]
Flow rate = Factor x Pressure difference

10. Case study 2: Single-sided ventilation
The Future Envelope 12 final event 20-21 May 2019, Bolzano
Inside
Outside
Horizontal section through vent unit
Vent unit
zone
Outside
Occupied zone
Perimeter zone
Office space
(adjacent spaces not shown)

11. Case study 2: Single-sided ventilation
The Future Envelope 12 final event 20-21 May 2019, Bolzano
Flow in
Flow out
Air velocity
Flow
out
Flow
in

12. Case study 2: Single-sided ventilation
The Future Envelope 12 final event 20-21 May 2019, Bolzano
For same geometry, pressure
loss or effective area inwards ≠
pressure loss or effective area
outwards.
Effective area inwards (also
input to dynamic thermal
model) calculated to be six
times less than original
design target.
Design impact of study:
Attenuators removed.
Energy dissipation rate
Flow
in
Flow
out

13. Heat flow through glazing and comfort conditions
The Future Envelope 12 final event 20-21 May 2019, Bolzano
g-value
Shortwave
radiation
Surface
convection
Longwave
radiation
Sun patch spread over dynamic thermal
model surface (changes location over time)
Inside surface
temperature of glass
uniform over all
surface (unless areas
are split)
Local shading
Key glass
properties

14. Case study 3: Heat flow through complex glazing system
The Future Envelope 12 final event 20-21 May 2019, Bolzano
Closed cavity façade (CCF) system
Automatic interstitial blind
operation in dynamic
thermal model (reduced
solar gain & glare control).

15. Case study 3: Heat flow through complex glazing system
The Future Envelope 12 final event 20-21 May 2019, Bolzano
• R&D with vendors to capture
heat transfer and gains with
required controls.
• Challenge to vary blind operation
with incident solar gains and
resulting daylighting levels.
• Challenge to vary internal
artificial lighting and associated
heat gains with blind operation.
• Similar performance to brise
soleil system which allowed floor
to ceiling glazing.
Model 1
Single external surface
with four layers
including blind
Model 2
Single external zone
with controls for blind

16. Case study 4: Impact of glass temperature on room air flow
Winter
Glass inside surface
temperature 9.3°C
Summer
Glass inside surface
temperature 31.2°C
All surface temperatures fixed values in
CFD taken from dynamic thermal model
The Future Envelope 12 final event 20-21 May 2019, Bolzano

17. The Future Envelope 12 final event 20-21 May 2019, Bolzano
Summer
Case study 4: Impact of glass temperature on room air flow
Glass temperature 31.2°C
fixed and uniformCool jet does not
reach occupied zone
Supply air 0.7m3/s @14.0°C

18. The Future Envelope 12 final event 20-21 May 2019, Bolzano
Winter
Case study 4: Impact of glass temperature on room air flow
Glass temperature 9.3°C
fixed and uniformWarm jet does reach
occupied zone
Supply air 0.7m3/s @23.0°C

19. The Future Envelope 12 final event 20-21 May 2019, Bolzano
Case study 4: Impact of glass temperature on room air flow
Winter
Fixed glass
inside surface
temperature
Air
Surface
Variable glass
inside surface
temperature

20. Case study 5: Condensation risk and multi-phased flow
The Future Envelope 12 final event 20-21 May 2019, Bolzano
Supply
Extract
Pool
Spa
Heated floor
Basement pool / spa room with light well to garden area above
Light well ~28°C air temperature,
~60% RH

21. Case study 5: Condensation risk and multi-phased flow
The Future Envelope 12 final event 20-21 May 2019, Bolzano
Solid
Pond water (assumed 0°C at top surface)
Air with
moisture
Light well materials and conjugate heat transfer results (CFD)
Does condensation drip off underside of acrylic?

22. T.water(in) = f [T.water(out), heat gain in pipe and through plant room, flow rate]
Case study 5: Condensation risk and multi-phased flow
The Future Envelope 12 final event 20-21 May 2019, Bolzano
water(out)
water(in)
water(out)
water(in)
Pond water model

23. Case study 5: Condensation risk and multi-phased flow
The Future Envelope 12 final event 20-21 May 2019, Bolzano
Light well condensation risk
• Moisture dynamics – slight fogging or large droplets forming and falling?
• Strategy was to increase thickness of acrylic and gauge complaints!

24. Summary and conclusions
• Dynamic thermal and CFD modelling are powerful approaches used
to drive building design.
• Understanding limitations of the adopted approaches supports
good interpretation and, therefore, development of better designs.
The approach could impact pass-fail judgements for the design.
• Current approach to wind pressures and resulting ventilating flows is
quite simplistic. Often complex, particularly when using non-
standard openings.
• Heat flow through glazing can also be complex. The way that the
inside surface temperature is calculated may impact the room air
flow characteristics.
• Heat, air and moisture transport can be combined into one detailed
assessment providing added insights.
The Future Envelope 12 final event 20-21 May 2019, Bolzano

25. Thank you for your attention!
www.interreg.net
Prof Darren Woolf
Hoare Lea / Loughborough University
FACEcamp is funded by European Regional Development Fund and Interreg V-A Italy-Austria 2014-2020.