Sustainable Research Project Site Context - Passivhaus
Crescenzago, Milan
N
1 A00
Site Context - Chosen Section for Passivhaus Analyisis * Not to Scale
University of Nottingham Sustainable Research Project
Thomas James Newton Student ID: 4339958
Module Convenor: Guillermo Guzman Dumont A sustainable research project for Crescenzago, Milan with a focus on the application of Passivhaus principles. Submitted in partial fulfilment of the requirements for the module SRP (K14SRP)
in the University of Nottingham Department of Architecture and the Built Environment
4. Individual Development
PASSIVHAUS
Passivhaus is an international energy performance standard and design tool that enables buildings to be designed and constructed to achieve exceptionally comfortable and healthy living/working conditions. Buildings under the Passivhaus standard are also designed to achieve a low energy demand and minimal carbon emissions. The standard is characterised by six fundamental design concepts and strict criteria set by the Passivhaus Institute, who oversee the accreditation of buildings to Passivhaus criteria. This section aims to apply Passivhaus design principles to the Crescenzago Plot A and to establish how well it can achieve Passivhaus certification.
4. INDIVIDUAL DEVELOPMENT
85
PASSIVHAUS PRINCIPLES AND STANDARDS
Some of the basic principles for the construction of Passive House.
4. INDIVIDUAL DEVELOPMENT
86
Site Context - Passivhaus
N
1 A00
Site Context - Chosen Section for Passivhaus Analyisis * Not to Scale
M ila n
-
M et ro
V ia
A
ng
el o
V ia
R
iz zo li
Pa lm
an
ov a
Site Context - Passivhaus Selection
V ia
C iv it a
ve c
N
2 A00
Location of Passivhaus Site Scale: Not to Scale
ch
ia
Orientation
CLIMATE FILE – LOMBARDIA-MILANO (1996-2005)
Climate characteristics • • •
Warm Dry summers: Avg. Temp above 10oC Cold Wet winters: Temp between -3oC and 18oC Four distinctive seasons
Design Aim: • •
Maximize heat gain during Winter Minimize heat gain during Summer
4. INDIVIDUAL DEVELOPMENT
90
COMPACT FORM – FORM FACTOR
Buildings that are used for residential
purposes usually a lower
demand for cooling and ventilation when compared to commercial buildings such as sports halls and cinemas. As a result, the volume of a room should be design
as compact as possible. The
compactness of a building is indicated by its form factor, which has a considerable influence on a buildings overall energy demand. Typically, it is favourable to to achieve a form factor ≤ 0.7. As a result, as the surface area decreases relative to the volume, Passivhaus benchmarks become easier to achieve. Manually, this can be calculated using the formula below:
Maintaining a low SA/V ratio has been a priority since the beginning of the project. Since the start, the form of the building was kept compact, with its elongated face orientated along the E – W axis. The form factor has not changed throughout all design
Form Factor: 1.98
iterations.
4. INDIVIDUAL DEVELOPMENT
91
COMPACT FORM – TREATED FLOOR AREA
TFA: 859m2
4. INDIVIDUAL DEVELOPMENT
92
THERMAL BRIDGE FREE CONSTRUCTION Thermal Bridge A thermal bridge can occur at a structural element in a construction, where there is
greater thermal conductivity in the
element than its adjacent materials. This creates a path of least resistance, causing heat transfer between the inside and outside of the building. This should be eliminated at all costs to maintain the integrity of the thermal envelope and mitigate heat losses. Floor Slab Cold bridging in the foundation is eliminated by ensuring structural elements do not perforate the thermal envelope. As shown in the
wall building section, The slab of concrete is isolated using expanded polystyrene of 120mm under its base, and 350mm under/around the concrete ring beam. This helps supports the load of the wall whilst also preventing torsion of the steel ring beam. Cavity Closers - Thermal Break
Window Cavity Closer
Thermal breaks are used on all windows and door frames as a means to
mitigate
heat
loss.
Thermal
breaks
have
low
thermal
conductivity, and separate the inner and outer layers of the frame. Door and window rafters are separated to further eliminate chances of thermal bridging.
4. INDIVIDUAL DEVELOPMENT
93
THERMAL BRIDGE FREE CONSTRUCTION
For the envelope considered, there is a thermal bridge risk area as shown in the left figure. This could occur if the the structural steel beams which have a high thermal conductivity surpass the thermal envelope. Since this could create a track for heat transfer to the outside of the building, it has been been excluded from the DesignPH analysis.
4. INDIVIDUAL DEVELOPMENT
94
AIRTIGHT BUILDING ENVELOPE Airtight barrier Climate Membrane
Airtight Membrane To comply with the Passivhaus approach, a continuous airtight barrier must be installed. This surrounds the buildings thermal envelope and structure, acting as both a vapour control membrane and air tight barrier. As shown in the top left figure, the barrier is positioned on the dry/warm side of the thermal envelope, preventing air and moisture from surpassing structural and insulative layers. Climate Membrane Shown in red in top left figure is also the wind barrier layer, which is used on the external side of the buildings thermal envelope. Its purpose is to prevent external (cold and damp) air from entering the structure. Design Integrity Passivhaus buildings often fail to achieve accreditation due to faults arising during the construction process which do not reflect PHPP design results. In particular, this is due to the integrity of the airtight membrane which often fails to remain intact both during and after construction. It is important to use specialist tapes when sealing junctions (door/window connections to wall). Finally, care must be taken to ensure the airtight seal is not pierced by tools/joints when plumbing and wiring.
4. INDIVIDUAL DEVELOPMENT
95
MECHANICAL VENTILATION WITH HEAT RECOVER (MVHR)
MVHR An Mechanical ventilation with heat recovery system allows air flowing into the house to be preheated. This works by extracting warm, low quality air from rooms (such as bathrooms) and using it to re-heat fresh air that is supplied to bed rooms and living areas. The operation of the MVHR unit cannot be modelled in DesignPH, and this exercise is typically conducted in more specialised software designed to model fluid dynamics. Further modelling can be conducted in PHPP which has only been modified slightly for the analysis of this site. Diagram showing MVHR unit extracting air from rooms with warm, low-quality air, removing some of the heat via heat exchange and redistributing fresh, re-heated air to the rest of the building.
A summary of results for the MVHR system for the final design iteration can be seen on the following pages.
4. INDIVIDUAL DEVELOPMENT
96
MVHR - VENTILATION DATA
Passive House planning:
VENTILATION
DATA
Building: Treated floor area A TFA
m²
Room height h
m
Volume for ventilation (A TFA *h) =
VV
m³
859 2.50 2148
(Areas worksheet)
(Worksheet Annual heating)
Type of ventilation system x
Balanced PH ventilation
Please check
Pure extract air
Infiltration air change rate Wind protection coefficients e and f Coefficient e for screening class No screening Moderate screening High screening Coefficient f
Several sides exposed 0.10 0.07 0.04 15
One side exposed 0.03 0.02 0.01 20
For annual demand:
For heating load:
Wind protection coefficient, e
0.07
0.18
Wind protection coefficient, f
15
15
Net air volume for press. test
0.60
0.60
2363
For annual demand:
For heating load:
1/h
0.00
0.00
1/h
0.046
0.116
Air change rate at press. test
n 50
Excess extract air Infiltration air change rate
n V,Rest
1/h
V n50
Air permeability
0.83
m³
q50
m³/(hm²)
Selection of ventilation data input - Results The PHPP offers two methods for dimensioning the air quantities and choosing the ventilation unit. Fresh air or extract air quantities for residential buildings and parameters for ventilation systems with a maximum of 1 ventilation unit can be determined using the standard planning option in the 'Ventilation' sheet. The 'Additional Vent' sheet has been created for more complex ventilation systems and allows up to 10 different ventilation units to be taken into account. Furthermore, air quantities can be determined on a room-by-room or zone-by-zone basis. Please select your design method here.
x
Ventilation unit / Heat recovery efficiency design (Ventilation worksheet see below) Standard design Multiple vent. units, non-res buildings (Worksheet Additional vent)
Average air exchange
Average air change rate
Extract air excess (Extract air system)
Effective heat recovery efficiency unit
Specific power input
m³/h
1/h
1/h
[-]
Wh/m³
1385
0.64
0.00
75.0%
0.45
SHX efficiency
Heat recovery efficiency SHX
0.0% h*SHX
0%
4. INDIVIDUAL DEVELOPMENT
97
MVHR - VENTILATION DATA
STANDARD INPUT FOR BALANCED VENTILATION Ventilation dimensioning for systems with one ventilation unit
Extract air requirement per room
m³/h
Total extract air requirement
m³/h
35 24.5 30 736 Kitchen 18 60 1800
m³/h
1800
Occupancy
m²/P
Number of occupants
P
Supply air per person
m³/(P*h)
Supply air requirement
m³/h
Extract air rooms Quantity
Design air flow rate (maximum)
Bathroom 18 40
Bathroom (shower only)
WC
20
20
Average air change rate calculation
Type of operation
Daily operation duration h/d
Maximum Standard Grundlüftung Minimum
Factors referenced to maximum
Air flow rate m³/h
1/h
1800 1385 969 720
0.84 0.64 0.45 0.34
Average air flow rate (m³/h)
Average air change rate (1/h)
1385
0.64
1.00 0.77 0.54 0.40
24.0
Average value
Air change rate
0.77
Warning: Fresh air quantities are clearly higher than the fresh air requirement; risk of overly dry air!
Selection of ventilation unit with heat recovery
x
Central Unit within the thermal envelope. Central Unit outside of the thermal envelope.
Heat recovery efficiency Unit hHR
Sortierung: WIE LISTE Ventilation unit selection
0.75
97ud
Specific power input [Wh/m³]
Application range [m³/h]
0.45
n.a.
Frost required
n.a.
Unit noise level < 35dB(A)
n.a.
Go to ventilation units list Conductance value of exterior air duct Length of exterior air duct
Y
Conductance value of exhaust air duct Y Length of exhaust air duct Temperature of mechanical services room (Enter only if the central unit is outside of the thermal envelope.) Effective heat recovery efficiency
hHR,eff
W/(mK) m
0.000
See calculation below
W/(mK) m °C
0.000
See calculation below Room temperature (°C) Avg ambient temp. heat. period (°C) Avg ground temp (°C)
75.0%
20 7.3 15.3
Energy recovery efficiency (humidity) hERV
4. INDIVIDUAL DEVELOPMENT
98
OPTIMAL USE OF PASSIVE SOLAR GAINS
Orientation A majority of the building, and in this case the selected thermal envelop faces South. This is due not only due to urban context, but maximize passive solar gain, a key Passivhaus design principle. Bedroom are also positioned on the South faรงade of the building to maximise natural light throughout the day, but particularly during the morning hours
Daylighting The floor plan is designed using an open plan living area including kitchen and dining. This enables these areas to receive an adequate amount of natural daylight provided from south facing windows.
4. INDIVIDUAL DEVELOPMENT
99
OPTIMAL USE OF PASSIVE SOLAR GAINS - SHADING
First Iteration
Use of Shading Extended balconies are used as shading devices which work to provide a shaded seating area for residents, but mainly to shade a part of the buildings thermal mass during summer. In the winter however due to the lower angle of the sun, the building will still receive ample light and thermal gains (“GreenSpec,” n.d.) The chosen envelope experiences shading from all directions particularly on the south facing façade. This is useful for mitigating overheating in the summer, but does not overshadow too much during the winter. Cantilever balconies were incorporated
in the
initial design to create shading on the glazing below. The first iteration of the design showed that the envelope was overheating. From the analysis, it was evident that Solar gains were extremely high and needed to be reduced. This was achieved by reducing the glazing ration and increasing shading.
4. INDIVIDUAL DEVELOPMENT
100
FIRST ITERATION EXAMPLE INPUTS - designPH
4. INDIVIDUAL DEVELOPMENT
101
FIRST ITERATION EXAMPLE INPUTS - designPH
4. INDIVIDUAL DEVELOPMENT
102
FIRST ITERATION EXAMPLE INPUTS - designPH
4. INDIVIDUAL DEVELOPMENT
103
OPTIMAL USE OF PASSIVE SOLAR GAINS - SHADING
1st Iteration
2nd Iteration
4. INDIVIDUAL DEVELOPMENT
104
OPTIMAL USE OF PASSIVE SOLAR GAINS - GLAZING
1st Iteration
2nd Iteration
4. INDIVIDUAL DEVELOPMENT
105
SUPERINSULATION – FINAL COMPONENTS
Roof
Windows
The roof system achieves a U-Value of 0.12W/m2K. It is
South: Windows
composed of a 200mm layer of polystyrene, extruded and
These are ideal for cool, temperate climates and spacers to
fully bonded and placed between the vapour control
mitigate thermal bridges. They have triple glazing and and are
membrane and water proof barrier. This helps to keep the
design by by ACO.
roof dry by maintaining insulation above it.
will achieve a U-value of 0.84 W/m²K.
North: 400 series casement windows. Used to reduce noise to create a calmer, quieter living space. These can reduce outside
Outer Walls
noise by up to 60%, making it ideal for a residential building of this scale. U-value of 1.13 W/m²K.
Most of the outer walls, exposed to ambient air will use Kingspan membrane which achieves a U-value of 0.13 W/m2K. The insulation in the system is a layer of rockwool, 280mm thick. Framing board is placed between the steel frame and then covered with 10mm of orientated strand board. Finally, the
breathable membrane is then covered by a terracotta
cladding.
Outer Doors External doors will achieve a U-Value of 0.5W/m2K. Doors will be slightly glazed, allowing a bit of light through on the northern façade. Glazing within the door will be triple glazed. Doors will have a profile of 97mm and will house a vacuum insulated panel.
4. INDIVIDUAL DEVELOPMENT
106
% IMPORVEMENTS â&#x20AC;&#x201C; TRANSMISSION HEAT LOSS (OPAQUE SURFACES)
4. INDIVIDUAL DEVELOPMENT
107
% IMPORVEMENTS â&#x20AC;&#x201C; TRANSMISSION HEAT LOSS (WINDOWS)
4. INDIVIDUAL DEVELOPMENT
108
% IMPORVEMENTS â&#x20AC;&#x201C; TRANSMISSION HEAT GAINS (WINDOWS)
4. INDIVIDUAL DEVELOPMENT
109
FINAL DESIGN
4. INDIVIDUAL DEVELOPMENT
110
COMPARISON BETWEEN 1ST AND LAST ITERATIONS
1st Iteration
Final Iteration
4. INDIVIDUAL DEVELOPMENT
111
ACTIVE SUMMER VENTILATION STRATERGY
SUMMER
Passive House planning:
VENTILATION
Building: Building volume: Max. indoor absolute humidity: Internal humidity sources: Results passive cooling Frequency of overheating: Frequency of exceeded humidity: max. humidity:
Building type:
2148 12 2 15.8% 17.0% 13.6
Heat recovery hHRV : Energy recovery hER: Subsoil heat exchanger h*SHX :
m³ g/kg g/(m²h)
at the overheating limit Jmax = 25 °C
75% 0% 0%
Results active cooling Useful cooling demand: 10.1 Dehumidification demand: 35.4
kWh/(m²a) kWh/(m²a)
g/kg
Summer background ventilation to ensure adequate air quality
Air exchange via vent. system with supply air:
1.20
1/h
Air exchange via extract air system
0.60
1/h
Window ventilation air exchange
6.48
1/h
HRV/ERV in summer (check only one field) None automatic bypass, controlled by temperature difference x automatic bypass, controlled by enthalpy difference always Specific power consumption (for extract air system)
0.20
Wh/m³
An active summer ventilation strategy is introduced to mitigate cooling demand. This is done by building users actively opening windows and increasing air ventilation. *See further suggestions for Frequency of overheating.
4. INDIVIDUAL DEVELOPMENT
112
ACTIVE SUMMER VENTILATION STRATERGY
Secondary calculation: Hygienic air exchange through window ventilation Estimation for window air exchange to ensure sufficient air quality Open duration [h/d]
Mast.Bed 0.2
Liv.Room 2
Climate boundary conditions Temperature diff interior - exterior Wind velocity
278 4
278 4
18 2.00 2.85
18 1.90 1.40
Description
Window group 1 Quantity Clear width Clear height Tilting window (check if appropriate) Opening width (for tilting windows)
K m/s
m m m
Window group 2 (cross ventilation) Quantity Clear width Clear height Tilting window (check if appropriate) Opening width (for tilting windows)
18 1.00 0.50 x 0.100
m m m
Difference in height to window 1
m Total
Result: Air exchange
1.49
4.98
0.00
0.00
0.00
0.00
6.48
4. INDIVIDUAL DEVELOPMENT
1/h
113
RESULTS - PASSIVHAUS STANDARDS
Passivhaus Certification Requirements
Plot A Passivhaus
Passed
Specific Heating Demand (SHD)
≤ 15 kWh/m2.yr
11 kWh/m2.yr
✓
Specific Cooling Demand
≤ 15 kWh/m2.yr
10 kWh/m2.yr
✓
≤ 10 W/m2
6.8 W/m2
✓
≤ 120 kWh/m2.yr
79.12 kWh/m2.yr
✓
≤ 0.6 ac/h @ 50 Pa
0.6 ac/h @ 50 Pa
✓
Standards
Specific Heating Load Specific Primary Energy Demand Air Changes per hour
Expected Requirements Super insulation
0.15 W/m2K
0.13 W/m2K
✓
Super windows
0.85 W/m2K
0.72 W/m2K
✓
Super doors
0.8 W/m2K
0.5 W/m2K
✓
Thermal bridging
eliminated
eliminated
✓
1m3/hm2
1m3/hm2
✓
>75% efficiency
>75% efficiency
✓
Air tightness MVHR Efficiency
4. INDIVIDUAL DEVELOPMENT
114
ADDITIONAL PHPP RESULTS - OVERVIEW
4. INDIVIDUAL DEVELOPMENT
115
ADDITIONAL PHPP RESULTS â&#x20AC;&#x201C; HEATING LOSSES AND GAINS
4. INDIVIDUAL DEVELOPMENT
116
ADDITIONAL PHPP RESULTS â&#x20AC;&#x201C; SUMMER VENTILATION
4. INDIVIDUAL DEVELOPMENT
117
FURTHER IMPROVEMENTS
Overheating Passive House planning:
SUMMER
VENTILATION
Analysis of the final model shows that although the envelope achieves Passivhaus standards, the frequency of overheating is still very high. Further design iterations will need to design overheating out whichBuilding: can be achieved through the following steps: Building volume: Max. indoor absolute humidity: Internal humidity sources:
Results passive cooling Frequency of overheating: Frequency of exceeded humidity: max. humidity:
2148 12 2
15.8% 17.0% 13.6
m³ g/kg g/(m²h)
at the overheating limit Jmax = 25 °C
Building type: Heat recovery hHRV : Energy recovery hER: Subsoil heat exchanger h*SHX :
75% 0% 0%
Results active cooling Useful cooling demand: 10.1
kWh/(m²a)
35.4
kWh/(m²a)
Dehumidification demand: g/kg
Summer background ventilation to ensure adequate air quality HRV/ERV in summer (check only one field) 1. Re-orientate the building: Solar gain is not the only way a Passivhaus heat heat, meaning design should not solely depend on it. As a Air exchange via vent. system with supply air: 1.20gains 1/h None automatic bypass, controlled by temperature difference
x
result, optimal orientation for Passive Solar Heating may not be as important as initially thought. The orientation slightly east facing which automatic bypass, controlled byis enthalpy difference always
increases the chance of excess solar gain, leading to the challenge of providing adequate shade. This could be designed out by facing further south. Air exchange via extract air system
0.60
1/h
Specific power consumption (for extract air system)
0.20
Wh/m³
ventilation “Solar air exchange 6.48 1/h 2. Do not heat the building withWindow windows: gain should not be maximised in a Passivhaus building, it should be optimised”.
3. Maintain sensible glazing ratio: It is recommended that windows on a south-facing should be a maximum of 25% of the external wall area. This is adequate for daylighting (except for very deep rooms.) Windows facing other directions should be much less than 25% of the external wall area. “As a rule of thumb glazing (excluding frames) should be around 15 – 20% of the TFA”. 5. Account for realistic occupancy. PHPP “uses a set level of occupancy to calculate internal heat gains” and as a result heat demand. This however is arbitrary and not accurate of how the building will actually be used. Forecasting building usage/occupancy could help better estimate internal heat gains and reduce overheating frequency. 7. Minimise building services heat loss. Account for hot water system heat gains when designing in PHPP to aid the iterative design process. 8. MVHR summer bypass: “If the air is hotter outside than inside, the heat exchanger should be used and not bypassed”. As applied in the current scenario, “heat exchange transfers heat from the incoming air to the outgoing air, cooling the air as it enters the building”.
4. INDIVIDUAL DEVELOPMENT
118
PASSIVHAUS ENTRY POP UP POSTER
4. INDIVIDUAL DEVELOPMENT
119
A3 TARMAC PASSIVHAUS ENTRY
4. INDIVIDUAL DEVELOPMENT
120