Sustainable Research Project - Extract

Sustainable Research Project Site Context - Passivhaus

Crescenzago, Milan

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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.

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PASSIVHAUS PRINCIPLES AND STANDARDS

Some of the basic principles for the construction of Passive House.

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Site Context - Passivhaus

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Site Context - Chosen Section for Passivhaus Analyisis * Not to Scale

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Site Context - Passivhaus Selection

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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

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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.

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COMPACT FORM – TREATED FLOOR AREA

TFA: 859m2

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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.

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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.

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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.

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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.

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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%

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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

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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.

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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.

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FIRST ITERATION EXAMPLE INPUTS - designPH

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FIRST ITERATION EXAMPLE INPUTS - designPH

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FIRST ITERATION EXAMPLE INPUTS - designPH

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OPTIMAL USE OF PASSIVE SOLAR GAINS - SHADING

1st Iteration

2nd Iteration

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OPTIMAL USE OF PASSIVE SOLAR GAINS - GLAZING

1st Iteration

2nd Iteration

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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.

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% IMPORVEMENTS â&#x20AC;&#x201C; TRANSMISSION HEAT LOSS (OPAQUE SURFACES)

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% IMPORVEMENTS â&#x20AC;&#x201C; TRANSMISSION HEAT LOSS (WINDOWS)

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% IMPORVEMENTS â&#x20AC;&#x201C; TRANSMISSION HEAT GAINS (WINDOWS)

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FINAL DESIGN

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COMPARISON BETWEEN 1ST AND LAST ITERATIONS

1st Iteration

Final Iteration

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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.

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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

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1/h

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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

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ADDITIONAL PHPP RESULTS - OVERVIEW

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ADDITIONAL PHPP RESULTS â&#x20AC;&#x201C; HEATING LOSSES AND GAINS

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ADDITIONAL PHPP RESULTS â&#x20AC;&#x201C; SUMMER VENTILATION

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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”.

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PASSIVHAUS ENTRY POP UP POSTER

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A3 TARMAC PASSIVHAUS ENTRY

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