Scott Tallon Walker - nZEB Design Discussion Talk Dec 2017

Scott Tallon Walker Architects
nZEB
The New Minimum Standard
“We cannot Solve our problems with the same
thinking we used when we created them.”
- Albert Einstein
Noel Hughes| 15th December 2017

Legislation
• Introduction
• EPBD
• Part L - UK
• Part L - Ireland
• Part L - Renovation
• Cost
nZEB Typology
• Domestic
• Apartment
• Office
• Education
• Sport Hall
• Retail
nZEB Design
Principles
• Form + Design
• Structural Types
• Solar
• Ventilation
• Construction
nZEB Tips +
Tricks
• Design Advice
• Resources Advice
• Management Advice
• Services Advice
• Design Risks
• Management Risks
• Construction Risks
nZEB | Chapters

nZEB | Introduction
nZEB Definition [EPBD (2010/31/EU) Article 2]
‘Nearly Zero-energy Building’ means a building that has a very high energy performance, as
determined in accordance with Annex I [of the EPBD].
The nearly zero or very low amount of energy required should be covered to a very significant
extent by energy from renewable sources, including energy from renewable sources produced on-
site or nearby;

nZEB | EPBD
Energy Performance of
Buildings Directive (EPBD)
The objective of the Directive is to
set a framework for the
application of minimum
requirements for the energy
performance of new buildings
across the EU.
• Member states to ensure that
all new buildings are “Nearly
Zero Energy Buildings” by 31st
Dec 2020
• Member states to ensure that
all new buildings owned and
occupied by Public Authorities
are `Nearly Zero Energy
Buildings’ after 31st Dec 2018
• Major Renovations to be at Cost
Optimal Level in Building Codes

nZEB | EPBD
EPBD Public Deadline
European Energy Performance of
Buildings Directive (2010/31/EU)
Article 09 states:
• all new buildings which
are owned or occupied by
Public Authorities need to be
nZEB the 31st December 2018
Note: “Occupied” is the
keyword, as it implies that
a premises must have a
valid nZEB Certificate of
Completion by 31/12/2018
for a public tenant to
occupy a new premises
without being in violation
of the EPBD and face fines
Allowing for the 21 day validation
period the last day for submitting
a non-nZEB compliant Certificate
of Completion is the 7/12/2017

nZEB | EPBD
EPBD + Renovation Works
Article 02 states:
• the total cost of the renovation
relating to the building
envelope or the technical
building systems is higher than
25 % of the value of the
building, excluding the value of
the land upon which the
building is situated;
or
• more than 25 % of the surface
of the building envelope
undergoes renovation;

nZEB | Part L
National Implementation
Article 4 states:
• Member States shall take the
necessary measures to ensure
that minimum energy
performance requirements for
buildings or building units are
set with a view to achieving
cost-optimal levels.
In Ireland and the UK, this is the
Part L energy building regulation.
Ireland UK

nZEB | Part L
UK and nZEB
The future requirements for nZEB
remain unclear in the UK. The UK
government is not expecting to
announce if the current
regulations will change before
spring 2018.
Scotland, Wales and NI
Scotland and Wales have
committed to meeting the nZEB
standard and to updating their
building energy standards as
necessary. However, progress
does not appear to be rapid
enough to deliver compliance by
the 2019 EU deadline
No information is available on
Northern Ireland’s progress to
nZEB. However, it is reasonable to
assume it is in line with the other
devolved regions

nZEB | Part L
London and nZEB
The Getting to Zero report, by the
London Energy Transition
Initiative (LETI) urged the Greater
London Authority (GLA) to make a
clear commitment to the ‘building
fabric first’ approach to energy
performance, for both heating
and cooling.
The report also recommends that
the current “zero carbon” targets
should be updated to be more
closely compliant with the nZEB
target by adopting international
building performance standards.
• Total energy requirements
should be in kWh/m²/yr,
replacing the current CO₂
emission methodology
• Also challenges the current
London Plan regarding carbon
saving. Namely gas CHP

nZEB | Part L
TGD Part L - Non
Domestic (2017)
To be applied 1st January 2019
• Provides an improvement in
performance in the order of
60% over TGD Part L (2008)
• Improved Fabric Specification
• Advanced Services and Lighting
specification
• Renewable Energy Ratio of
20%
TGD Part L - Dwellings
(2018)
• Public Consultation
Early 2018
• Application
2019 (subject to regulatory
process)

nZEB | Part L
TGD Part L - Non
Domestic (2017)
• Renewables requirement will be
included as Renewable Energy
Ratio (RER) = 20%
• Represents a very significant
level of energy provision from
renewable energy technologies
Regulation L5 (b)
• “Where the MPEPC of 1.0 and
MPCPC of 1.15 is achieved an
RER of 0.20”
• “Where the MPEPC of 0.9 and
MPCPC of 1.04 is achieved an
RER of 0.10”
• Renewable energy sources
include Photovoltaic, Heat
Pumps (Air source and ground
source), Biomass, Solar
Thermal ,Primary Energy
Savings from Combined Heat
and Power (CHP), Renewable
district heating

nZEB | Part L
Reference Building
Values
Current Conservation of
Fuel and Energy -
Dwellings 2011
Current Conservation of Fuel
and Energy – Non- Dwellings
2008
New Conservation of Fuel and
Energy – Non- Dwellings 2017
Improvement
Opening Areas
Offices and Shops - Windows and
Pedestrian Doors are 40% of the
total area of Exposed Walls
Offices and Shops - Windows and
Pedestrian Doors are 40% of the
total area of Exposed Walls
U- Values: Walls 0.21 W/m²K 0.27 W/m²K 0.18 W/m²K 33%
U- Values: Roof 0.16 W/m²K 0.16 W/m²K 0.15 W/m²K 6%
U- Values: Floor 0.21 W/m²K 0.25 W/m²K 0.15 W/m²K 40%
U- Values: Windows DEAP Table 6a 2.20 W/m²K 1.40 W/m²K 36%
Glazing Solar Transmittance DEAP Table 6a 0.72 0.40
Thermal Bridging
Default = 0.15 W/m2K
ACD = 0.08 W/m2K
Add 16% to fabric heat loss
Y-Value = Actual Length of Key
Junctions x Advanced psi value
Air Permeability 5 m³/(hr.m²) Floor Area 10 m³/(hr.m²)
5 m³/(hr.m²) Floor Area ≤250m²
3 m³/(hr.m²) Floor Area ≥250m²
30%
70%
Renewable Energy Ratio
10 kWh/m²/yr to heating or
4 kWh/m²/yr to electrical
None 20%
Proposed Performance requirements for Part L nZEB Buildings - Reference Building Fabric

nZEB | Part L
Building Type
Primary
Energy
CO₂
emissions
Building Energy Rating
Energy
Improvement
CO₂
Improvement
kWh/yr/m² kg/yr/m² Indicator BER % %
Office (Natural Ventilation) 2F 62.8 12.6 0.3 A2 65 65
Office (Air Conditioned) 2F 100.1 20.7 0.5 A3 66 67
Office (Natural Ventilation) 4F 60.1 12.1 0.3 A2 63 64
Office (Air Conditioned) 4Fl 98.6 20.5 0.5 A3 65 66
Hotel (Air Conditioned) 348.1 65.3 0.5 B1 66 67
Retail (Air Conditioned) 178.3 38.2 0.4 A3 68 67
Mixed Use 89.3 18.2 0.3 A2 69 60
School 57.6 11.2 0.4 A3 50 51
Proposed Energy and Carbon Dioxide emissions performance for Part L nZEB Buildings

nZEB | Part L
Par 2.3.4
The following improvements are
normally considered to be cost
optimal and will typically be
economically feasible when more
than 25% of the surface area of a
building is being upgraded
• Upgrading heating systems
more than 15 years old
• Upgrading cooling and
ventilation systems more than
15 years old
• Upgrading general lighting
systems that have an average
lamp efficacy of less than 40
lamp lumens per circuit-watt
and that serves greater than
100m²
TGD Part L (2017) - Major
Renovations
Par 2.3.2
When calculating the proportion
of surface area undergoing
renovation the area of the whole
building external envelope should
be taken into account including
i.e. external walls, roofs, floors,
windows, doors, and roof
windows and lights
Works to the surface area of the
building include the following:
• Cladding the external surface of
the element
• Drylining the internal surface of
an element
• Replacing windows
• Stripping down the element to
expose the basic structural
components and then
rebuilding to achieve all the
necessary performance
requirements.
Building Type
Primary
Energy
BER
kWh/yr/m²
Air Conditioned Retail 338 E1
Natural Ventilated Offices
and Other Buildings
124 B3
Air Conditioned Office 180 C3
Air Conditioned Hotel 342 E2
Schools 60 B1
Other Air Conditioned
Buildings
338 E2
Other Naturally Ventilated
Buildings
124 B3
Major Renovation - Cost Optimal Level

nZEB | Part L
• Par 1.5.5: Commissioning
The key elements of a
commissioning plan, identifying
the systems that need to be
tested and the tests that will be
carried out and should be
developed at the design stage
• Par 1.5.4.2: Airtightness Testing
Air pressure testing should be
carried on all development sites
to show attainment of backstop
value of 5 m³/(hr.m²). The
tests should be carried out by a
person certified by an
independent third party
• Par 1.5.6.1: Ductwork Leakage
Leakage testing should be
carried out on systems served
by fans with a design flow
greater than 1m³/s
Other Part L (2017)
Requirements
• Lighting should meet minimum
recommended standards for
efficacy and controls
• Par 1.3.6: Overheating
Assessment
The designer should specify
what the indoor comfort
specification and perform an
overheating assessment to
ensure overheating is avoided
BMS
• Boilers over 100kW to have
BMS controls and AC systems
over 200m² to have BMS
controls
• A full BMS system will provide
full zoned time control and
weather compensation where
applicable, frost protection or
night set-back optimization and
monitoring and targeting

nZEB | Part L
Cost Impact
Independently access construction costs give
this increase at:
• Office 2% – 2.4%
• Air Conditioned Hotels 4.6% – 5.4%
• Air Conditioned Retail 2.4% – 3%
• Natural Ventilated Mixed Use 1.3% – 1.5%

nZEB | Typology
Key Question
What will an
nZEB look like?
Vandermaelen
Development,
Brussels

nZEB | Domestic Example
Silken Park
Location: Citywest, Co. Dublin
Completion: April 2018
BER: A2 (47-49.6 kWh/m²/yr)
Passive House Certified
Developer: Durkan Residential
Architect: BBA Architecture
Building type:
•Phase 3 of a private development,
consisting of a mix of terrace, semi-
detached and detached houses.
•Twenty-four 2-bed terraced/ semi-
detached houses (84m²),
•Twenty-nine 3-bed terraced/semi-
detached houses (109m²),
•Five 4-bed semi-detached houses
(120m²)
•One 4-bed detached (126m²)
•All 59 houses will come pre-wired for EV
charge points
•Roofs are designed to take the weight of
a solar PV system covering the whole roof

nZEB | Apartment Example
Roebuck Student Residences
Location: UCD
Size: 3097m2
Completion: 2010
BER: A3
Heat Demand: 12kWh/m²/yr
Primary Energy: 114kWh/m²/yr
PH Certified
Architect: Kavanagh Tuite Architects
Building Info:
• 6 storeys high, housing 300 students
• Residence style accommodation with en-
suite student rooms, kitchenette and
living on either side of a spine corridor
• External walls formed in structural
concrete, cast with permanent magnetizes
formwork requiring decoration finish only
Roof: 0.150 W/(m2K)
Walls: 0.170 W/(m²K)
Floor: 0.150 W/(m2K)
Glazing: 0.800 W/(m2K)
Curtain Wall: 1.200 W/(m2K)
Air Permeability: 0.600 ACH

nZEB | Office Example
Enexis Regional Office
Location: Maastricht, Netherlands
Size: 5912 m2
Completion: 2013
Cost: €6,715,500
Primary Energy: 34.7kWh/m²/y
Architect: Kent Pedersen Architects
Building Info:
• BREEAM excellent
• First Energy-Neutral design certificate in
the Netherlands
• The building has energy-efficient
lighting, daylight control, presence
detection
• PV cells on the roof
Climate Control: Demand Controlled
Solar Water Heater: 13.3m²
PV: 1406m²
Cooling: Free Cooling
Ventilation: Balanced

nZEB | Office Example
GouweZone
Location: Gouda, South Holland
Size: 2747 m2
Completion: 2012
% of Renewables: 74%
Architect: EGM Architects
Building Info:
• A energy-neutral office development
• Completely CO2 neutral and uses 70%
less energy than typical office buildings
• All electric
• Tenants offered a multi-year contract
with a fixed all-in price in terms of
energy costs.
Heating: Electric Heat Pump
Delivery: Underfloor Heating and
Concrete Core Activation
PV: 620m²
Cooling: Free
Ventilation: Balanced

nZEB | Education Example
CREST
Centre for Renewable Energy & Sustainable
Technologies
Location: Enniskillen
Size: 455 m2
Completion: 2014
PH Certified
Architect: Paul McAlister, The Barn Studio
Building Info:
•Large areas of glazing to the south assist
with solar gain and allows natural light to
penetrate deep into the floor plan
• Reduces the amount of artificial light
required to the exhibition spaces.
•Utilises air to water heat pump, with
underfloor distribution
Roof: 0.160 W/(m2K)

Plein Oost School
Location: Haarlem, Noord-Holland
Size: 2521 m2
Completion: 2014
% of Renewables: 92%
Architect: Kristinsson
Building info:
• The school is energy-neutral
• Building houses two schools with
outdoor space and gym, a playgroup and
an after-school care centre
• Solar panels are installed with an east-
west orientation at an angle of 10
degrees
• The school board signed an agreement
with the municipality to finance the extra
investment , this is earned back through
lower energy and maintenance costs
PV: 672m²
Cooling: Heat Pump 27 MJ /m²
Ventilation:Balanced

Centre for Medicine
Location: University of Leicester
Size: 9863 m2
Completion: 2014
Cost: £42,000,000
PH Certified
Architect: Associated Architects
Building Info:
• BREEAM Excellent
• Reduced annual energy bills by 80%.
• Heating from local district heating
• Minor cooling from pipes in slabs
• Hot water from local electric heaters,
successfully avoided distribution losses
• Largest green wall in the UK outside of
London
Roof: 0.122 W/(m2K)

nZEB | Sport Hall Example
Södra Climate Arena
Location: Växjö, Sweden
Size: 3589 m2
Completion: 2012
PH Certified
Architect: Kent Pedersen Architects
Building Info:
• Tennis hall with four tennis courts, a
cafe, conference rooms, a gym,
changing rooms and technical facilities
• The hall is heated by air, the rest of the
rooms have radiators
• The entire system is demand-controlled
Roof: 0.068 W/(m2K)

nZEB | Retail Example
Tesco
Location: Tramore, Waterford
Size: 3970 m2
Completion: 2008
Primary Energy: 758 kWh/m²/yr
PH Certified
Architect: Joseph Doyle Architects
Building Info:
•First certified Passive House supermarket
in the world
•Waste heat of refrigeration plant
connected with ventilation system
• Uses 45% less energy than a
supermarket of a similar size saving 420
tonnes of carbon dioxide per annum
Roof: 0.15 W/(m2K)
Floor: 3.68 W/(m2K)
Perimeter insulation only - Ground below
building acts as a heat storage

nZEB | Retail Example
Quirke’s Pharmacy
Location: Clonmel, Tipperary
Size: 229m2
Completion: 2014
BER: A2 (46.75 kWh/m²/yr)
Heat Demand: 12 kWh/m²/yr
Primary Energy: 150 kWh/m²/yr
PH Certified
Architect: PassivHaus Architecture
Building info:
•Combined pharmacy at the ground level
and an apartment above
•Third non-residential passive house
building in Ireland
•Original building was over 200 years old,
and in poor condition before renovation
•Came in on budget, and opened a month
ahead of schedule
Roof: 0.097 W/(m2K)

nZEB | Databases
Passive House Project Database
http://www.passivhausprojekte.de
Netherlands Enterprise Agency
Energy Efficient Construction Database
https://www.rvo.nl/initiatieven/overzicht/27008

nZEB | Design Principles
Design is not just what it
looks like and feel like.
Design is how it works.
- Steve Jobs
These are principles are just ‘Rule of Thumb’
But if you know how the rule works and why
it is there – they you know what to do if
want to design something different

nZEB | Form + Design
Orientation
Basics: Sun rises in the East and sets in
the West
Obvious as it may seem, it is important to
remember that during winter the sun
actually rises south of east and in the
summer rises north of east.
So in the summer north facing facades will
very briefly be exposes to the sun.
It is important to consider the suns path
when design areas which may develop
micro-climates: sunken or sheltered area,
sun rooms + gardens and atrium spaces.
It is also important to consider the
potential impacts of glare from the low
winter sun when developing BREEAM and
LEED projects.

Form Optimisation
Basics: Compact building use less
energy
The greater the surface areas of a building
envelope, the more energy it will lose
through the fabric, thermal bridges and air
permeability.
A sphere has the smallest surface area by
volume (form factor) of any form. In the
winter a single storey home could use up
to 25% more energy compare to a two
storey home of the same floor area
The best form is a slightly elongated solar-
orientated form that provides a balance
between solar heat gains and heat losses

Thermal Comfort
Every person has a different opinion on
what is a comfortable internal temperature,
typical a temperature range of 18-22˚C
with a humidity of 40-60% is comfortable
for a human being.
Building services typical aim to provide an
internal environment of:
• 20˚C @ 50% RH
Any internal temperature of over 25˚C is
considered to be overheating.
Note: TGD Part L does not have a
requirement to address
overheating in a building.
However, Passive House
requires the number of hours in
a year that exceeds 25°C to be
limited to 10% annually.
+ Keeping cool what should be kept cool
+ Keeping warm what should be kept warm
+ Without energy consumption
= Comfortable Environment

Rationalise the Layout
Basics: Cold Rooms to the North, Warm
Rooms to the South – use
buffer zones
It is wise to plan a building such that
rooms that require little to no heating or
are only occupied occasionally (toilets,
store room, bedrooms etc) are located on
the northern face with ‘active’ room to the
southern face.
This rule is based on the ‘servant and
served’ principle of space planning.

Fabric First
A phrase that will become more prevalent
thanks to nZEB. ‘Fabric First’ is the
principle that the majority of a building
heat is lost and gained through its fabric.
Insulation is a barrier to heat flow both
inward and outwards of a structure and is
required to maintain an appropriate level of
thermal comfort.
Basics: The basic rule is to wrap the
buildings external envelope
continuously (including under
the floor slab) with 200 -
300mm of insulation
Significant amounts of energy
is lost due to the infiltration of
external air, mostly through
poor quality construction
junctions which are not airtight.
Insulation is the cheapest and most
effective way to save energy.
Insulation first, then Renewables

nZEB | Structural Types
Thermal Mass
High thermal mass building elements will
absorb heat slowly and store it. The store
heat will then be released slowly into the
building
In buildings with high thermal mass, the
highest indoor temperatures will occur in
the early hours of the morning, typically a
number of hours after the highest outdoor
temperatures have been reached. This
slow response time is known as the
‘Thermal Flywheel Effect’
Note: In a highly insulated building
with a stable internal
temperature the benefits of
thermal mass can be limited.
Without internal temperature
fluctuation, the stabilising effect
of thermal mass is irrelevant.

nZEB | Structural Types
Lightweight Structures
Lightweight structures with a low thermal
mass are better suited to building with an
intermittent use, which needs to be heated
quickly or are less sensitive to thermal
comfort requirements.
These buildings need to be well insulated
and benefit from a quick response heating
systems.
Heavyweight Structures
Heavyweight structure favour building
which is in constant use as internal
temperature swings are naturally
dampened and the heat gains are retained.
It is important to plan for the time lag
between the maximum internal and
external temperatures to prevent potential
overheating in the summer or valuable
heat energy being flushed away by the
ventilation system or night cooling

nZEB | Solar
Solar Shading
As designers, there are a range of solutions
for solar shading and prevent unwanted
solar gains
External shading devices perform better
than internal methods as they completely
prevent the sun’s rays from entering the
building. Internal blinds, while preventing
solar glare, will not prevent overheating
Basics: Southern solar shading should
be horizontal due to the high
angle of the summer sun.
East or West shading should be
vertical to shade against the
low angle of the sun.
Sothern Shading East/ West Shading

nZEB | Ventilation
Natural Ventilation
There are two main forces that underpin
natural ventilation systems, they are Wind
and thermal Buoyancy.
In Ireland and the UK, the external wind
conditions is the most dominating deciding
factor in the daily levels of natural
ventilation for most buildings.
Wind meeting a building creates a pressure
difference between its windward and
leeward faces, and this drives ventilation
Note: As most natural ventilation are
wind or external air pressure
drive, on still days they will
either operate at a greatly
reduce performance or be
completely ineffectual.

nZEB | Ventilation
Single-Sided Ventilation
For spaces that have only access to a
single external façade, a maximum of 6m
can be effectively ventilated.
Allow for an opening area of at least 5% of
the floor area to be ventilated.
Cross Ventilation
Cross ventilation relies on the pressure
difference between the windward and
leeward facades. It is effective for spaces
who’s depth is no greater then 5 times the
ope height. Again allow for an opening
area of at least 5% of the floor area to be
ventilated.
Stack Ventilation
Stack Ventilation relies on buoyancy of air
and requires a temperature difference of
over 2 ˚C to be inside and outside.
• Rule-of-Thumb:
In Ireland/UK, all year around natural
ground floor ventilation will need a
five-storey high stack
Single –Sided Ventilation
Stack Ventilation
Cross Ventilation

nZEB | Ventilation
Mechanical Heat Recovery
Through the use of a mechanical
ventilation system with a heat recovery
unit (MVHR), it is possible to extract heat
from the exhaust air and use it to warm
incoming fresh air.
Such systems need a well-insulated
building with an airtight building envelope
Note: Unless a building achieve an
airtightness of a minimum of 3
Air Changes per Hour – MVHR
will not be cost effective
At higher ACH rates an MVHR
unit will use more energy in run
its air pump that any energy
recovery from the exhaust air

nZEB | Ventilation
Night Time Purging
Thanks to the high energy performance in
nZEB. And combined with an increase in
airtightness levels (1.0 ACH should be
achievable, the minimum Passive House
requirement is 0.6 ACH) will potentially
increase the risk of overheating.
A cost-effective mean of cooling a building
is night purging.
This can either be mechanical or natural
ventilation system and can be a smart
system controlled by a BMS or a simple as
an opening windows at night.
It is a highly efficient, simple and cheap
method of cooling a structure and reducing
the risk of overheating
No Night Time Purging Night Time Purging

nZEB | Construction
Thermal Bridges
Thermal bridging occurs in building
envelopes where there are gaps or breaks
in the insulation envelope creating
pathways for heat loss.
Thermal bridging also occurs in building
envelopes when materials with higher
thermal conductivity (such as steel, timber
and concrete) are used. These materials, if
not properly detailed, will create pathways
for heat to bypass the thermal insulation.
Types of Thermal Bridges:
• Linear Thermal Bridges
• Repeating Thermal Bridges
• Non-Repeating Thermal Bridges
• Geometrical Thermal Bridges
Heat always looks for the
path of least resistance

nZEB | Construction
Airtightness
It is vital to reduce air infiltration in a
structure. The additional costs of air
tightness measures is negligible but are
entirely reliant on build quality.
TGD Part L Non-Domestic 2017 requires a
minimum of airtightness of 3 ACH.
If a design team wishes to achieve a
higher rated building performance and the
10% renewable target – A high airtightness
value will be required.
Note: The graph shows the annual heat
gains and losses of two version of a
domestic dwelling, with the only
difference being airtightness.
The first house has a 5 Air change
per hour and the second has the
minimum Passive House requirement
of 0.6 ACH.
The result is an energy saving of
40% thanks to a reduction in heat
losses.
32.6
7
5
4.9
14.2
14.2
4
3.2
8.2
8.1
7.4
7.4
11.4
7.7
34.6
13.7
22.4
18.3
25.8
20.4
0
10
20
30
40
50
60
70
80
90
5.0 ACH Losses 5.0 ACH Gains 0.6 ACH Losses 0.6ACH Gains
Comparing Airtightness
Ventilation Thermal Bridge Windows Floor
Roof External Walls Non-useful Heat Gains Heat Demand
Internal Heat Gains Solar Heat Gains

nZEB | Tips + Tricks
It is always cheaper to do
the job right the first time
- Phil Crosby
Some basic thing to watch out
for on a nZEB project

nZEB | Design Advice
Keep it Simple
Building occupants will ignore or override
complex controls and systems. And over
time they will forget how to effectively
operate a system, typical ruining and
energy saving or adding to ‘wear and tear’.
People feel more comfortable when they
have control over their environment. So
any design must be robust, intuitive and
simple.

Reduce Energy demand through
Design
The building sector accounts for about
40% of total energy consumption and 38%
of the CO2 emissions in the US and about
27% of the emissions in the UK are
attributed to the buildings
Strategies to reduce energy consumption
are highly dependant on building type and
a clients requirements.
This means that the Architects is best
placed to reduce the initial building energy
requirements through clever space
planning and an understanding of how
building services/ systems will be used
Review the ASHRAE Advanced Energy
Design Guides for further information

Minimising Thermal Bridging
The need for structural integrity, and the
need to allow light and access into a
building leads inevitably to the use of
different materials with different thermal
properties.
Good design of each of these details to
minimise the thermal loss is crucial both to
keep heating demand down and to avoid
cold spots where condensation might form.
Have as must of the structure
as possible inside the thermal
envelope
No penetrations means no
Thermal Bridges
Retrofit Window Details
1. Solid Block Wal – No Insulation
2. External Insulation to Wall +
Large Thermal Bridge through
existing Concrete Sill
3. External Insulation to Wall, which
Window within the Insulation
Layer

nZEB | Resources Advice
Develop a Library of Standardised
Thermally Modelled Details
TGD Part L – Non Domestic (2017) will
require all key junction detail to be
Thermally Modelled by an accredited
accessor
The NSAI, have established a national
register of Thermal Modellers (there are
currently on 14 in the country).
The typical cost of to model a detail is
€200-300 for a 2D thermal model and
€300-400 for a 3D thermal model. With a
2-3 day turnaround time for each detail.
It is prudent to develop an internal library
of accredited standard details to minimise
cost and time delays

nZEB | Management Advice
Real Collaboration
Due to the added complexity of achieving
the nZEB energy standard, a collaboration
between the construction team is essential.
Full buy-in from the design team is
required. Primary and secondary structures
are the principal causes of thermal bridging
and the oversizing of mechanical service is
a major source of additional cost.
Most important the main and sub-
contractors need to be fully aware of the
requirements and the additional pressure
they put on on-site quality control.
nZEB cannot be delivered with a
‘business as usual’ attitude

nZEB | Management Advice
Fixed Design at Construction
The TGD Part L – Non-Domestic (2017)
requirements for thermal modelling of all
details in addition to the complications of
NEAP software and the Renewables
requirements. This will result in any change
to the building strategy during construction
being onerous and potentially costly.
For example, if a Contractor changes the
specified wall insulation material with a
similar product with a different U-value and
thermal bridging properties (y-factor).
Then a new thermal model will have to be
produced and the building energy
requirements reassessed.
There is considerable risk related to
undeveloped details or service strategies
being issued for tender.
The old motto remains true:
If you haven’t drawn it - You
haven’t thought about it

nZEB | Services Advice
Simplify Services
If a technology drive approach is taken to
meet nZEB requirements, it is estimated
that it could add 20-30% to the
construction cost.
The principles behind a ‘Fabric First’
approach is to minimise the need for M+E
services through good design and a high-
performance building fabric.
Further savings can be made if service
routes are thought of early in the design
process. Plant spaces should be centralised
to facilitate the shortest and most efficient
route runs.
Plants requirements should be established
early in the design to ensure that they are
not oversized as this will add unnecessary
cost and increase the buildings energy
usage

Minimising HVAC Usage
Air condition systems consume a significant
amount of energy and design consideration
must give address any overheating risks.
Offices will be most at risk of overheating.
But with an appropriate use of solar
shading and building strategies such as
night cooling. HVAC can be greatly reduced
or phased out entirely.

Appropriate Renewables
In an urban location, most nZEB will
mostly like rely on electric based
Renewables, such as PV panels and Heat
Pumps (typical ‘air to water’ or ‘air to air’)
Micro Wind is typical not cost effective in
Ireland and extremely rarely in an urban
location
Note: Micro Wind turbines are designed to
operate at a wind speed of 10-12 m/s.
Average Irish wind speed at 10m above
ground is 4-6m/s (less in urban
environments). The performance of
wind turbines at these speeds drops
significantly
Biofuels maybe be cost-effective for rural
development, but is dependant on the
space available for the storage of fuels
The Future is Electric

nZEB | Design Risks
Overheating
With the increase in U-value requirements
and airtightness under TGD Part L - Non-
Domestic (2017), the potential for
overheating will increase.
There are a number of definitions for
overheating; CIBSE defines it as:
‘internal temperature of 28˚C is surpassed
for over 1% of the time’ and Passive House
as: ‘25˚C is surpassed for over 1% of the
time’. It is recognised that an internal
temperature of above 35˚C will create a
significant danger of heat stress.
The Irish TGD does not define overheating
but the designer should specify what the
indoor comfort they wish to achieve and
perform an overheating assessment.
However, any overheating risk can be
reduced or eliminated through the
appropriate design decisions

nZEB | Design Risks
Mould Growth
The mould grows over a wide range of
temperatures, but favours
temperatures similar to those inside
building and wall build-ups.
Thanks to the warmer internal
environments created by the TGD Part L -
Non-Domestic (2017) standard, mould will
thrive if moisture movement across build-
ups is not properly considered.
Irish building regulation has a minimum
requirement for surface temperature (fRSI),
the requirement of which have to be
covered by the designer's professional
indemnity insurance.
The surface temperature factor is
established by dividing the measured
surface temperature by the difference in
temperature between the inside and
outside air (20˚C as per ISO standards).
See adjacent table for TGD Part L - Non-
Domestic (2017) fRSI requirements.

nZEB | Design Risks
Setout of Services
In order to meet the new TGD Part L -
Non-Domestic (2017), all primary service
distribution routes will need to be
insulated, as well as many secondary
services.
For example, the heat gains in a large
building from uninsulated domestic hot
water can be substantial, particularly
during summer months and contribute to
overheating. If a ø32mm pipe needs 25mm
insulation, the resulting ø82mm pipe may
increase the width requirements of service
zones and studwork
The setout of pop-up positions to floor slab
and penetrations to external walls will all
need to take account of the requirements
for additional insulation

nZEB | Management Risks
Tender + Fear Factor
A substantial upskilling of onsite contractor
is required in order to meet the nZEB
standards. While there are a number of
programmes nationally aim at this, they
have not seen widespread adoption by the
construction industry.
The need to educate key onsite member
will inevitably effect tender prices and
construction programmes. There is also the
prospect of contractors applying a ‘fear
factor’ sum - overpricing works which they
are unsure or unfamiliar with.
When drawing up tender documentation,
clarity must be provided on
• The high level of construction quality
• The additional level of inspections
(recommended multiply airtightness
test to ensure a consistent
performance)
• Any additional foreman responsibilities
• All damages or bonuses associated with
meeting key requirements

nZEB | Management Risks
Buying Design Risks
The majority of cost-saving measures
regarding the implementation of nZEB are
made at both the initial design and design
development stages of the project
programme.
Combined with the TGD Part L - Non-
Domestic (2017) implementation date of
early 2019, presents a potential risk when
bidding for projects at Construction stage
only.
There will be significant manhours and cost
in upgrading a substantively completed
design to the new TGD Part L - Non-
Domestic (2017) standards.

nZEB | Construction Risks
On-Site Quality Control
The importance of commitment from on-
site contractors to the nZEB process cannot
be understated.
Contractors who have successfully
completed low-energy projects have
recommended the used of continuous
onsite inspect and the appointment of an
onsite champion. Areas of concern would
be:
• Airtightness
• Continuity of Insulation
• Integrity of vapour control layers
Suitable clause will need to any contract to
ensure onsite construction quality (with
appropriate awards and damages) and key
dates for inspection will need to be
included in the construction programme
Be prepared for “I have been building
for XX years” arguments

Scott Tallon Walker ArchitectsNoel Hughes| 15th December 2017
Good Luck
You’ll be fine

Scott Tallon Walker - nZEB Design Discussion Talk Dec 2017

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Scott Tallon Walker - nZEB Design Discussion Talk Dec 2017