SAP

UNTANGLED

An introductory guide to
SAP for new homes
CONTACTS ACKNOWLEDGEMENTS

Further copies of this guide are The Zero Carbon Hub is very grateful to the following contributors/
available as a PDF download organisations for their involvement in developing this Guide.
from www.zerocarbonhub.org
Author
Zero Carbon Hub Gary Nicholls, Briary Energy Consultants
Layden House
76-86 Turnmill Street Project Advisors
London EC1M 5LG Rob Pannell, Tessa Hurstwyn, Ben Griggs, Zero Carbon Hub
T: 0845 888 7620
E: info@zerocarbonhub.org Graphic Design
Richard Hudson, www.richardhudson.me
Briary Energy Consultants
A solution service offering cost Steering Group
effective, value engineered SAP Chris Carr, Federation of Master Builders/Carr & Carr Builders
calculations. Sam Dawe, Innovaré Systems
T: 0203 397 1373 Darren Dancey, Crest Nicholson
www.briaryenergy.co.uk Jonathan Ducker, Kingspan
Chris Hall, BRUFMA
SIG360 Technical Centre Dyfrig Hughes, National Energy Services
Provides a service offering that Sarah Kostence-Winterton, MIMA
focuses on helping customers Mike Leonard, Building Alliance
deliver energy efficient buildings. Ian Mawditt, fourwalls
Central to SIG360 is an easily Andrew Orriss, SIG Plc
accessible impartial team of Graham Perrior, NHBC
technical specialists, who draw Dale Saunders, Taylor Wimpey
on an extensive range of Barry Turner, LABC
products in providing the most Luke Whale, C4Ci
cost effective build, suited to
your preferred building style.

Ideal Boilers
A leading supplier and
manufacturer of high efficiency
gas boilers with market leading
SAP performance. Made in Britain
with a range of warranty options
and a UK wide customer service
team on hand seven days a week,
when you choose an Ideal boiler
we provide you with ultimate
peace of mind. Our, award
winning boilers include combi,
heat only and system boilers.
CONTENTS

INTRODUCTION2 DESIGN STAGE

SUMMARY – POTENTIAL ISSUES INFORMATION REQUIRED

LEADING TO NON COMPLIANCE 3 – OVERVIEW 8

WHAT IS THE SAP CALCULATION, DRAWINGS AND TECHNICAL SPECIFICATION 9

AND WHAT IS IT USED FOR?  4
INFORMATION REQUIRED
SAP PROCESS 5 – LINEAR THERMAL BRIDGING 10

COMMUNICATION IS KEY TO PART L INFORMATION REQUIRED

COMPLIANCE6 – GLAZING 11

WHAT SHOULD I KNOW BEFORE I HAVE PROVIDED ALL THE INFORMATION,

APPOINTING A SAP ASSESSOR? 7 WHAT HAPPENS NEXT?  12

FACTORS THAT AFFECT THE ASSESSMENT 13

POTENTIAL TECHNOLOGY ADDITIONS 16

THE OVERHEATING CHECK IN SAP 18

BUILD STAGE

WHAT IS REQUIRED TO PRODUCE THE AS BUILT

COMPLIANCE CERTIFICATE AND EPC? 19

EXAMPLE IMPLICATIONS OF CHANGES

DURING CONSTRUCTION 20

USEFUL LINKS 22

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INTRODUCTION

SAP Untangled is aimed at the SME Builder and or alterations to the design at construction stage is
gives an overview of the Building Regulations Part highlighted. The information required by the
L1A compliance process with respect to the SAP assessor to complete the As Built SAP assessment
calculation. and produce the EPC for the dwelling is outlined.

This Guide is intended as a basic introduction to the The aim of the Guide is to make the SAP assessment
SAP assessment process and the information required process more transparent to those who may not be
by the assessor and Building Control in order to fully aware of its significance in achieving Building
achieve compliance with certain aspects of Building Regulations Part L1A compliance.
Regulations Part L1A and the successful production of
an Energy Performance Certificate for the home. The information in this Guide is based on the
current versions; Part L1A 2013, and SAP 2012.
The Guide starts by giving an overview of the SAP However most will also be applicable to dwellings
assessment process, and pointers on how to being built to Part L1A 2010. Note that the
choose your SAP assessor. information is only applicable to properties in
England. Scotland and Wales have different
It then goes on to detail the information required by regulations and are not covered by this Guide.
the SAP assessor at Design Stage in order to
produce a prediction of the energy use and carbon This Guide is one of a series of good practice
emissions of the dwelling. Simple cost effective guides that are aimed at addressing the
ways of meeting fabric energy efficiency and performance gap and improving the design,
carbon targets are explored. procurement and construction quality of new
homes. All publications in the series are available
The importance of the SAP calculation result for from the Zero Carbon Hub website.
compliance and the effects of product substitution

Acronyms

BFRC DOCEA HETAS OCEA

British Fenestration Domestic On Heating Equipment On Construction
Rating Council Construction Energy Testing & Approval Energy Assessor
Assessor Scheme
CPD TER
Continuing Professional EPC MCS Target Emission Rate
Development Energy Performance Microgeneration
Certificate Certification Scheme TFEE
DER Target Fabric Energy
Dwelling Emission Rate FGHRS OCDEA Efficiency
Flue Gas Heat On Construction
DFEE Recovery System Domestic Energy WWHR
Dwelling Fabric Assessor Waste Water Heat
Energy Efficiency Recovery

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SUMMARY – POTENTIAL ISSUES
LEADING TO NON COMPLIANCE

DESIGN STAGE AS BUILT STAGE

OO Poor drawings and lack of information or OO Poor drawings and lack of information or
specification. specification.

OO The ventilation strategy is not defined. OO The ventilation strategy is not defined.

OO “Minimum” U-values specified, without proof. OO “Minimum” U-values specified, without proof.

OO Heating details are not specified meaning OO Heating system and controls not installed as
assumptions need to be made, potentially per the Design Stage calculation inputs.
making the result poorer than if correctly
specified heating and controls are used.
OO Specified junction details not built to meaning
PSI-value inputs need to be adjusted.
OO Realistic air leakage figures are not assumed.
These should be set according to the
OO The air pressure test result is higher than
ventilation strategy, Building Regulations and
assumed in the Design Stage calculation.
past experience of air pressure test results
achieved.
OO Changes made to the dwelling design and/or
product substitution (if not communicated to
OO SAP conventions not adhered to, meaning
assessor during build.
incorrect DER calculation is produced.

OO Window specifications do not match design, in

terms of U-value, frame factor and g-value; or
BFRC figures specified, but different windows
installed.

OO Secondary heating installed when not in

original design.

OO SAP conventions not adhered to, meaning

incorrect DER calculation is produced, and
EPC audit failure.

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WHAT IS THE SAP CALCULATION,
AND WHAT IS IT USED FOR?

The Government Standard

Assessment Procedure (SAP)

SAP is the Government’s Standard Assessment

Procedure for the calculation of predicted energy use Building Regulations Part L1A
and resulting carbon dioxide emissions from a Compliance Criteria
dwelling. It is used as the main compliance tool for
Building Regulations Part L1A, to satisfy Criterion 1 and Criterion 1: Achieving the Target
provides information to satisfy Criterion 2 and Emissions Rate (TER) and Target
Criterion 3. It is also used to produce the Energy Fabric Energy Efficiency (TFEE) – i.e.
Performance Certificate (EPC) for the completed That DFEE ≤ TFEE and DER ≤ TER
dwelling. Criterion 2: Limits on design flexibility
- the thermal performance of building
The SAP calculation is based on the energy elements and efficiencies of services
balance of the dwelling over the course of a year should not fall below minimum values
taking into account a range of factors that
contribute to energy efficiency, and is based on a Criterion 3: Limiting the effects
standardised occupancy profile. of heat gains in summer
Criterion 4: Building performance consistent
The SAP calculation is undertaken via approved with the Dwelling Emission Rate (DER) and
software packages and is used to provide the Dwelling Fabric Energy Efficiency (DFEE)
following information for a new dwelling:
Criterion 5: Provisions for energy
OO The Target Emissions Rate (TER) efficient operation of the dwelling

OO The Target Fabric Energy Efficiency (TFEE)

OO The Dwelling Emissions Rate (DER)
A SAP assessment is carried out at two stages in
OO The Dwelling Fabric Energy Efficiency (DFEE) the design and construction of a new dwelling:
OO The SAP rating
OO At Design Stage, with a submission to Building
OO The Environmental Impact Rating Control before work starts on site

Building Regulations Approved Document Part L1A OO At As Built Stage, with a final submission on
gives guidance as to how to reasonably completion of the dwelling
demonstrate to Building Control that a building has The two submissions can be used by Building
been designed and constructed in compliance with Control to check compliance with required targets.
the appropriate energy efficiency requirements of A clear connection must be evident between
for new-build dwellings. Additional industry product specifications and the data inputs into the
produced guidance is available, for example NHBC SAP software. The As Built submission is required
Foundation ‘Part L 2013–Where to Start’ guides, to produce the EPC for the completed dwelling.
NF58 and NF59.

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SAP PROCESS

The Process in Stages

A sign of a good assessment is where information can clearly be Note: ‘Client’ here could be the Builder
seen to have flowed between the developer and the assessor, or another member of the design /
and that this matches what has actually been built / installed. development team.

Builder / design Build commences to Assessor calculates

team produce agreed specification. the As Built result
drawings and Any specification from information
changes during the
specification and Design Stage
build, checked with
the assessor assessment

SAP assessor Air tightness testing Assessor checks As

review of supplied carried out and Built compliance –
information results forwarded to if fails, discussion
assessor of remedial works

Review of initial On completion client Assessor lodges

assessment and requests As Built EPC with
advice on calculation from accreditation
compliance assessor scheme and
Landmark Registry

Assessor issues final Assessor reviews Assessor issues As

Design Stage supplied information Built SAP and EPC
calculation to client and requests any to client, who
forwards to Building
additional required
Control, with
supporting evidence

Client forwards Signed confirmation

Design Stage of As Built
compliance specification from
documents to client to assessor
Building Control

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COMMUNICATION IS KEY
TO PART L COMPLIANCE

Communication with your SAP assessor, across all aspects of the design and
construction process, is vital to ensure the SAP calculation accurately represents
bb Quick fact
the design and subsequent construction of the dwelling; and that in both cases
A common cause
compliance is achieved. Commercial pressures can sometimes negatively
of issues with
impact the quality and accuracy of assessments and information provided, so
compliance at
involving an assessor throughout the process can have significant benefits.
As Built stage
is product
Do not be afraid to ask the SAP assessor for references. If you are working on a
substitution. For
development that requires particular product knowledge, e.g. renewables, then
example, changing
ask the assessor to relay their experience in this area, such as the percentage
a high efficiency
of their work that involves renewable or low carbon technology.
product for a
poorer performing
It is easy to feel that energy assessments are an obstacle or tick box exercise
product.
with assessors often instructed too late in the design process. Remember that
SAP is a compliance tool. Interaction with the assessor, early in the design
process, will allow a dialogue should your design initially fail to comply.

A clear path to follow in terms of achieving compliance would be a fabric first

bb Quick fact
approach, followed by fit and forget technology and then renewables or other
For a building that
low carbon technology. However, bear in mind that the SAP assessor may not
contains more than
be a trained designer, so be aware of the extent of the assessors’ knowledge,
one dwelling, such
particularly on product specification and application, when trying to get a
as a terrace of
dwelling to achieve Design Stage compliance.
houses or an
apartment block,
During the build process, communication back to the assessor, when making
compliance can be
any changes that could affect the energy efficiency of the dwelling, is
calculated based
paramount. Ideally, check that the revised assessment will pass, before
on the floor-area-
implementing any changes. Do not be tempted to tell the assessor whatever is
weighted average
needed in order to get the As-built assessment and EPC produced. This will
of the TER/DER
create issues with Audits (which are carried out by the assessor’s accreditation
and TFEE/DFEE for
body) and subsequently issues with the accuracy of the EPC.
all the dwellings in
the building.

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WHAT SHOULD I KNOW BEFORE
APPOINTING A SAP ASSESSOR?

Example building
regulation
compliance report
aaIshave
the SAP assessor qualified and do they
Professional Indemnity insurance?

Your SAP assessor needs to be OCEA / OCDEA / DOCEA accredited,

(depending on scheme) to produce an EPC from an As Built SAP
assessment. It is recommended to use an accredited assessor throughout
the process and the status of the assessor can be checked on the
Landmark website: https://www.epcregister.com/searchassessor.html

Accredited professionals will also require at least £50,000 in ongoing

Professional Indemnity insurance, in order to remain a registered assessor.

aaWhat is the extent of the service being

offered and what are the fees?

The fee will depend on the service being offered. A basic service would
be for the assessor to enter the information you provide into the SAP
software to tell you whether the design complies or not, and then, based on
the information you provide, to produce an As Built version and EPC on
completion of the dwelling (if the dwelling is compliant).

An elevated level of service may be beneficial to you. For example, engaging

a knowledgeable assessor as a consultant early in the design stage, could
bb Quick fact often save money on the build cost, but may be subject to additional fees.

A SAP assessor HOWEVER, bear in mind that not all assessors will be energy efficiency
must complete a experts and they may not be sufficiently knowledgeable to identify
minimum of 10 appropriate solutions, or might even suggest options that would assist
hours of CPD per compliance without investigating their appropriateness or practicality. It is
year to remain therefore important to ascertain the competency and knowledge of the
certified. assessor before engagement.

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DESIGN STAGE

INFORMATION REQUIRED –
OVERVIEW

aaWhat information should

the drawings show?

Ideally fully dimensioned design stage

drawings showing the following:

OO The building’s form –

plans, elevations, sections
OO Linear thermal bridging details,
if available
OO Opening sizes, type and orientation
OO The amount of low energy lighting
OO Dwelling orientation –
site plan with North point shown
OO Site address
OO The drawings need to be sufficient for aaWhat information should
the specification show?
an assessor to accurately take-off
dimensions. OO The thermal insulation of the building
fabric, including material build ups
sufficient to allow U-values to be
calculated.

aaWhat additional information

might be required? OO If available, U-value calculations
produced by competent persons in
accordance with BR443
OO Any Planning conditions relating to
renewable or low carbon technologies, or OO Proposed heating and hot water system,
a stated percentage improvement over controls and the fuels used to provide
Building Regulations Part L1A. heating and hot water.
OO Any procurement deals that are in place, OO Materials to be used in the construction
that dictate the choice of materials or
OO Proposed level of air tightness of the
products to be used.
dwelling
OO Proposed ventilation system
OO Any additional technologies that
influence the outcome for example,
waste water heat recovery, flue gas heat
recovery, photovoltaic cells etc.

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DESIGN STAGE

DRAWINGS AND
TECHNICAL SPECIFICATION

Questions to Address
bb Quick fact
Below is a list of areas to address to ensure the assessor has sufficient
There is no British
information on the drawings and specification in order to carry out the Design
Standard applied to
Stage SAP assessment.
architects
drawings, in the
Is there a key to the wall types Is the ventilation position
same way that
used in the construction? and type shown?
there is for
Usually on the plan See Building Regulations Part F for
engineering
information and advice
drawings, so
Are all the openings labelled?
drawings will often
Can be on plan or elevation Are the corridors heated,
differ in information
in apartment blocks?
and layout.
Does opening information include If so, then an SBEM calculation is
sufficient information regarding required for the corridor areas
U-values, g-values, frame type,
glazing emissivity, air gap size; Is there a site plan
whether argon or air filled showing orientation?
Usually in the specification North point can be shown on
dwelling plans instead
Are doors opaque or glazed?
Openings are treated differently for Are the controls detailed?
solar gains depending on the Usually in the specification along with
percentage glazing – the heating. Or separate heating design.
is this information adequately
transferred to the assessor? Is there any secondary
heating noted?
Are the room types labelled? e.g. Log burner
e.g. Utility room
Are there working chimneys?
Are the wet-rooms detailed, Sometimes dummy chimneys are
showing shower or bath? included to the roof only, for
e.g. Electric Shower aesthetic reasons

Are the openings dimensioned? Are chimney and flue

Window schedule could be provided sizes obvious?
Any additional open flues need to be
Are the heating and hot accounted for
water systems detailed?
Usually in the specification Are there section Drawings?
Required to ascertain ceiling heights
Is there a lighting plan?
Percentage of low energy lights

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DESIGN STAGE

INFORMATION REQUIRED –
LINEAR THERMAL BRIDGING

A thermal bridge (sometimes called a cold bridge) is

a localised weakness or discontinuity in the thermal
envelope of a building. They generally occur when
the insulation layer is interrupted by a more
conductive material. Improving junction details to
reduce linear thermal bridging will help achieve
Building Regulations compliance and is one
component in achieving healthy low energy homes.

There are two types of thermal bridges in buildings

– repeating and non-repeating. Repeating thermal
bridges are taken account of in the U-value
calculations for the building elements.

The remaining non-repeating or linear thermal

bridges are dealt with by PSI-values. These occur at
junctions between elements, such as a wall and a
floor or a window and a wall. At these locations heat
is more able to transfer through the construction,
resulting in greater heat loss from the dwelling and
Example of Junction Detail
localised ‘cold spots’ in the building envelope. The
and associated PSI-value
energy lost through linear thermal bridging is
Images © Scottish described by the PSI-value of the junction detail
Government multiplied by the length of the junction.

Various sources exist to obtain PSI-values for the

building junctions of interest, for input into the SAP
calculation (and aid design of the junctions themselves);

OO Generic industry sponsored libraries covering

bb Quick fact the common building types e.g. LABC
Registered Construction details or Scottish
Thermal bridges standards Accredited Construction Details.
can account for
OO Individual product or building system
20-30% of the heat
manufacturer sponsored libraries, covering
loss in a typical
specific building products/systems.
new build home.
As homes become OO Bespoke PSI-values calculated by ‘competent
better insulated persons’ for specific developments.
thermal bridges
become even more For more information see the Zero Carbon Hub
significant. Thermal Bridging Guide and NHBC Foundation
Part L 2013 How to Start Guides.

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DESIGN STAGE

INFORMATION REQUIRED –
GLAZING

It is important that the correct information regarding the glazing is provided to

the SAP assessor. The information your assessor will require will be based on
three routes:

Manufacturer is Manufacturer is SAP tables, if the

appointed and has appointed and has manufacturer is
supplied: supplied: not appointed:

BFRC certified Glazing type – is it Glazing type – is it

U-value and g-value double / triple double / triple
glazed, argon filled, glazed, argon filled,
low E glass? low E glass?
g-value (solar What is the frame
transmittance) material?
Frame Factor What is the overall
U-value?
Overall U-value
bb Quick fact
The British
Fenestration Rating
Common Pitfalls
Council (BFRC)
provides
OO Changes in frame type, during construction, can cause compliance issues.
independent
For example, changing from uPVC to aluminium or composite windows, will
verification of the
alter the U-value and frame factor.
energy efficiency
of windows. OO Changing from a BFRC rated glazing, to a ‘Manufacturers’ specified rating will
change the assessment.
OO Changing the overall U-value or g-value of the glazing, will affect the
assessment result.
Note: it is common for
window manufacturers
There may be confusion over the U-value supplied by the manufacturer, as this
to promote the ‘centre-
can take three forms:
pane’ U-value of a
window rather than the OO The U-value measured through the centre of a glazing unit alone – ‘centre-pane’
more realistic ‘overall’
OO The U-value of the window frame alone.
U-value, and this can
cause issues with OO The overall U-value of the window including glazing unit and frame – ‘overall’
the accuracy of the
information presented The overall U-value is the value required by the assessor, so care needs to be
to the assessor taken to make sure the correct value is provided.

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DESIGN STAGE

I HAVE PROVIDED ALL THE

INFORMATION, WHAT HAPPENS NEXT?

aaIdesign
have the desired specification and correct
stage drawings, now what?

The assessor will enter the data into the approved software. At this
stage the assessor will be able to indicate if the dwelling meets
compliance. A sign of a good assessment is where information can
clearly be seen to have flowed between the developer and the assessor.

Over the course of a build, any assumptions should be replaced with

known parameters, and it is essential that any changes from
assumptions to proposed are checked before implementing, to avoid
costly mistakes that can result in the dwelling failing to comply. For
example, switching heating systems during build but not consulting the
SAP assessor until the dwelling is completed – and finding it now fails.

There are currently six approved software providers for SAP

calculations, but not all provide EPC lodgement in house.

These are (program name in brackets):

OO Bryter Digital (Energy Design OO National Energy Services Ltd

bb Quick fact Tools SAP 2012 Calculator) (NHER Plan Assessor)
OO Elmhurst Energy Systems OO RUSFA
Air pressure tests of (EES Design SAP 2012) (SAPPER)
completed dwellings
are required in OO JPA TL Ltd OO Stroma Certification
accordance with the (JPA Designer) (FSAP 2012)
specific requirements
set out in Part L. If no In addition to the approved software providers above, there are a
more than 2 number of accreditation schemes for the assessor.
dwellings are being
erected on a site it is
possible to avoid the
need for pressure
testing if an
aaDoes Part F of the Building Regulations
(ventilation) affect my Part L strategy?
airtightness value of
15 is used in the SAP The ventilation strategy does affect the SAP calculation. The type of
calculations. system (e.g. background ventilators and intermittent extract fans;
However, this will passive stack ventilation; continuous mechanical extract (MEV);
make compliance continuous mechanical supply and extract with heat recovery (MVHR)),
considerably harder the airtightness target of the dwelling, and the presence of any
to achieve. chimneys or flues are the main aspects which influence the result.

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DESIGN STAGE

FACTORS THAT AFFECT

THE ASSESSMENT

The SAP calculation is based on the energy

balance of the dwelling over the course of a year aaCan the choice of boiler
influence the DER?
taking into account a range of factors that
contribute to energy efficiency: Yes – the type, make and model of the
boiler will influence the resulting
OO Materials used for construction of the dwelling efficiencies calculated in SAP. So if the
boiler has been chosen at Design Stage,
OO Thermal insulation of the building fabric
this needs to be conveyed to the assessor.
OO Airtightness and ventilation characteristics of the
dwelling, and ventilation equipment installed Note that two combination boilers with the
same overall SEDBUK efficiency may lead
OO Efficiency and control of the heating system(s)
to different DER outcomes due to potential
OO Solar gains through openings differences in “summer” and “winter”
seasonal efficiencies of those boilers.
OO The fuel used to provide space and water
heating, ventilation and lighting
At As Built stage and for the EPC
OO Energy for space cooling, if applicable production, there is a requirement to
confirm the installed boiler, cylinder size
OO Renewable energy technologies
and heat loss and all must be evidenced.
The calculation is independent of factors related to
the individual characteristics of the household
occupying the dwelling, for example:

OO Household size and composition;

OO Ownership and efficiency of particular domestic
electrical appliances;
OO Individual heating patterns and temperatures.

It is able to do this by using standardised

occupancy, heating patterns and internal
temperatures.

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DESIGN STAGE

FACTORS THAT AFFECT

THE ASSESSMENT

aaWhat about renewable energy

technologies – can they help? aaDoes installing a secondary
heat source cause problems
with compliance?
The installation of renewable energy
technologies will help reduce the DER of Unless a particular make and model is
the dwelling. The choice of technology will specified, the SAP default tables must be
be partly dictated by the site location and used. Specifying a make and model will often
layout. Ideally renewables will be used to show a higher efficiency than the default but
complement a good fabric specification and the efficiency and test standard of the
in any case the TFEE will need to be met. specified heating is required. Aside from the
efficiency of the secondary heat source, the
It is advisable to take expert advice on the presence of a chimney or flue for the
options and specific design of any system. appliance will also affect the SAP result.

Technologies to consider include: Unless you have a room sealed log burner,
a secondary heat source is likely to make
OO Photovoltaic cells (PV)
the SAP result worse.
OO Solar thermal (solar hot water)
There is a lot of conflicting information
OO Air source heat pump (ASHP)
regarding claims of efficiency (both gross
OO Ground source heat pump (GSHP) and net efficiencies might be quoted by
salesmen), which can be misleading. As
and rarely: stated above, make and model of specified
heating, together with efficiency and test
OO Small scale wind turbines
standard are needed. For example, HETAS
OO Small scale hydro-electric power is the official body recognised by
Government to approve biomass and solid
The critical inputs into the SAP calculation fuel heating appliances, fuels and services.
varies depending on technology, but your
assessor will be able to advise what Note that if there is a chimney or flue
information needs to be provided to them. provided but no appliance actually installed,
for the purposes of the SAP calculation it is
assumed that if there is an unconnected gas
point then a gas fire with efficiency of 20%
is present, and if no gas point then a solid
mineral fire with an efficiency of 37% is
present.

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DESIGN STAGE

FACTORS THAT AFFECT

THE ASSESSMENT

aaCan boiler controls

influence the outcome? aaWhat about
heating controls?

Using a delayed start thermostat, weather or Time and temperature zone control on the
load compensator will improve the DER. The heating system can also improve the DER.
specific product needs to be in the SAP This could take the form of:
Product Characteristics Database to be
applied to the calculation, so check this with OO Separate plumbing circuits, either with
your assessor before specifying. their own programmer, or separate
channels in the same programmer, or
These products can typically improve the
OO Programmable TRVs or communicating
DER by around 1.5%
TRVs that are able to provide time and
temperature zone control (conventional
TRVs without a timing function provide
only independent temperature control). In
this case the device must be located in the
SAP Product Characteristics Database.
Both cases are subject to the conditions in
the SAP Technical Document and apply if
there are at least two zones in which heating
times and temperatures can be controlled
independently of each other.

In the case of direct-acting electric systems,

including underfloor heating, it can be
achieved by providing separate temperature
and time controls for different rooms.

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DESIGN STAGE

POTENTIAL
TECHNOLOGY ADDITIONS

Waste Water Heat Recovery (WWHR)

Typically a waste water heat recovery system works WWHR should be planned in early or wet room
by extracting heat from the water that the shower layouts may not allow efficient installation and full
or bath sends down the drain. This heat is used to benefit. Two showers can be connected to the
warm the incoming mains water, reducing the same WWHR system provided that the length of the
energy required by the boiler to heat the water up drain pipe between shower and WWHR is not
to temperature. WWHR typically take the form of a excessive (generally less than 3 metres). Bear in
long vertical copper pipe, where the warm water mind they need to be installed below the shower,
runs alongside the colder mains water to exchange and in back to back installations, they may clash
the heat. It is a fairly simple device, with no with other services. For bungalows or apartments,
electrical components, no pumps or controllers, there is a shower tray option, although this is not as
and so it requires very little maintenance. efficient as the pipe version. Note that WWHR
systems are not compatible with instantaneous
electric showers.

There are three different system configurations, with

System A providing the maximum energy saving. In
this system the output of the heat exchanger is fed
to both the shower and combination boiler or hot
water system. Consult a manufacturer for advice.

With Waste Water

Heat Recovery, it is
important to match
the correct type and
application to the
heating system.

Images © Shower Save

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DESIGN STAGE

POTENTIAL
TECHNOLOGY ADDITIONS

Flue Gas Heat Recovery Systems (FGHRS)

Flue Gas Heat Recovery Systems takes advantage of the heat within the waste
flue gasses resulting from the combustion of gas in the boiler. This recovered
heat is used to preheat the cold water entering the boiler, thereby lowering the
amount of energy needed to warm the water up to the required temperature.
It can be applied to mains gas, LPG or oil condensing boilers.

The flue gas heat recovery system requires very little maintenance, with no
need for mains electricity. These systems should be planned in early as there
are additional space requirements for the FGHRS. Some boilers have the system
built in, and in others it takes the form of a “top box”. It is important that the
specific boiler and FGHRS are compatible so check this with the manufacturer or
seek further advice.

Systems can be either a “wet” or “dry” version

Image © Ideal Boilers

Image © Zenex

Wet version Dry version

Stores the condensate normally expelled into the The device works by using the flue gases which
atmosphere through the boiler flue. Heat from are already hot to pre-heat the incoming cold
this condensate is recycled to pre-heat water water as it passes through. This pre-heated
coming into the boiler from the cold mains water then enters the combination boiler by the
supply. The energy saved is greater in the wet standard connection.
version than the dry.

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DESIGN STAGE

THE OVERHEATING
CHECK IN SAP

SAP contains a basic “overheating check” at Appendix P. The calculation gives an

assessment of whether the building has a low, medium or high risk of overheating
during the summer months. However, it is a basic compliance check only and is
based on monthly averages so if there is a risk of overheating it will not be able to
give information on why, or what might be done to mitigate the risk.

Building Control use the outcome of the assessment as evidence that Criterion 3
of Part L1A has been met – i.e. that reasonable provision has been made to limit
heat gains and that the building does not have a “high” risk of overheating.

aaThe home buyer requires air conditioning,

can this cause a problem for compliance?

Cooling systems use energy and will therefore negatively effect the DER.
The type of system, Energy Efficiency Ratio and area served needs to be
entered into SAP in order to get an accurate DER figure. The use of
passive cooling measures should be considered first, with mechanical
cooling and air-conditioning installed where other measures cannot
ensure acceptable indoor temperatures are maintained.

aaIhow
have a large area of south facing glazing,
can I reduce the overheating risk?

OO If possible reduce the amount of south facing glazing in the design.

OO Include external shading such as window overhangs.
OO Include external shutters, preferably light in colour.
OO Use glazing with a lower BFRC g-value (solar transmittance). However,
bear in mind that it will worsen the DER, so it is a fine balance.
Note: overheating
OO Increasing the thermal mass can help to smooth out internal should be considered
temperature changes over the course of a day, but stored heat will at design stage, with
need to be removed, for example by night time ventilation. buildings at higher
risk potentially
OO Add blinds to the windows – but there is no guarantee that these will
undergoing a more
actually be fitted by an occupant, so should not be used in the
rigorous overheating
calculation unless specified.
assessment, for example
Note that these measures (apart from blinds) will affect the DER and DFEE. by the use of dynamic
thermal modelling.

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BUILD STAGE

WHAT IS REQUIRED TO PRODUCE THE AS

BUILT COMPLIANCE CERTIFICATE AND EPC?

bb Quick fact aaWhat is required to produce the As Built

compliance certificate and EPC?
U-value
calculations should The assessor will require the following information in order to produce an
be submitted to As Built compliance document and EPC. This information must then be
Building Control made available should an audit be carried out on the assessment by the
with the SAP SAP assessor’s scheme provider.
calculation. They
should be carried OO If available, or if there have been changes since the Design Stage
out by persons – As Built drawings (plans, sections, elevations).
competent to do OO OR a statement from the developer or equivalent person that the
so, and in dwelling has been constructed in accordance with the design
accordance with specification provided to the assessor and where applicable, written
BR443. confirmation to the assessor that the specific products have been
used in the dwelling concerned.
OO As Built specification, if different from the Design Stage specification
– Detailed construction information describing all the materials used
bb Quick fact in the building fabric. All services including space/water heating,
ventilation, lighting renewables and any other technologies, including
To complete an As
MCS certificates
Built assessment,
it is essential that OO U-value calculations (likely to be produced by your assessor) –
a Client advises the U-value calculation data sheet including construction layers
assessor when (materials,thickness and thermal properties) and U-value corrections
changes have been
OO Statement from developer or equivalent person confirming the
made from the
window properties as built or a certificate based on BFRC
information given
methodology
at Design Stage.
OO A copy of the air leakage pressure test certificate. For a dwelling that
was tested, test certificate for that dwelling. For a dwelling not
tested, test certificates for dwellings of the same type that were used
to derive the average. Testing must be conducted by a suitably
qualified person. (Or confirmation that testing was not required).
OO Confirmation of linear thermal bridging construction details and
PSI-values or own calculated values
OO Waste Water Heat Recovery Systems – Suitable evidence of correct
installation, e.g. Installation checklist and certificate

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BUILD STAGE

EXAMPLE IMPLICATIONS OF
CHANGES DURING CONSTRUCTION

Below are examples of potential Not building to the construction details for linear thermal
compliance issues created during bridging claimed in the SAP calculation at Design Stage will
construction. likely lead to increased heat loss and issues with achieving
DER and DFEE compliance at As Built stage if PSI-values
have to be amended in the calculation.

PROBLEM TO AVOID INSULATION MISSING BELOW DPC

OUTSIDE
COLD SPOT =
CONDENSATION
INSULATION
BRICK MISSING

INSULATION

BLOCK

INSIDE

PLAN OF SUB FLOOR VENT BLOCKING INSULATION

PROBLEM TO AVOID MISSING EDGE INSULATION

INCORRECT OR MISSING
EDGE INSULATION

THERMAL BRIDGE
INSULATION
MISSING FINISH
SCREED
INSULATION
FLOOR STRUCTURE

POOR DETAILING IMPRACTICAL

TO BUILD ON SITE

SCREED BRIDGING THRESHOLD

Refer to the ‘Builders’ Book’ published by the Zero Carbon Hub for further information and tips on how
to avoid these problems.

20 SAP UNTANGLED | ZERO CARBON HUB

BUILD STAGE

EXAMPLE IMPLICATIONS OF
CHANGES DURING CONSTRUCTION

PROBLEM TO AVOID HEAT LOSS THROUGH UNINSULATED PIPES

PIPES NOT Not insulating the primary pipework could have over a
INSULATED 2% negative effect on the DER and would mean that the
installation does not meet the recommended minimum
standards set out in the Building Services Compliance
Guide. In addition, the uninsulated pipework could
contribute to a summertime overheating problem.

Running uninsulated pipework in internal corridors in

apartment blocks can cause an overheating issue, and
not just in the summer months.

PRIMARY PIPEWORK NOT INSULATED

PROBLEM TO AVOID SUBSTITUTING THE BOILER ON SITE

Changing the boiler, without re-running the SAP

calculation can cause issues with compliance, even if
the overall SEDBUK figures are the same. This is
particularly evident in combination boilers where the
efficiency of hot water production can differ, meaning
the DER could be affected.

Not installing full zonal controls, weather compensation

or delayed start thermostat, when these have been
assumed in the Design Stage calculation, will have a
negative effect on the DER.

Swapping fuel types will have huge implications –

e.g. installing an electric boiler where the Design Stage
calculation was based on gas

Always check with the SAP assessor before changing the specification between Design Stage and As
Built Stage, especially when substituting products.

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USEFUL LINKS

Accredited Assessor List Domestic Ventilation Compliance Guide

https://www.epcregister.com/searchassessor.html http://www.planningportal.gov.uk/buildingregulations/
approveddocuments/partf/associated
Zero Carbon Hub Builders Book
http://www.zerocarbonhub.org/full-lib NHBC Foundation ‘Part L 2013 – Where
to Start’ guides, NF58 and NF59
Zero Carbon Hub Services Guide http://www.nhbcfoundation.org/Publications/Guide/
http://www.zerocarbonhub.org/full-lib Part-L

Zero Carbon Hub Thermal Bridging Guide LABC Registered Construction Details
http://www.zerocarbonhub.org/full-lib https://www.labc.co.uk/registration-schemes/
construction-details
Building Regulations Part L (2013):
Conservation of Fuel and Power Scottish Standards – Accredited
http://www.planningportal.gov.uk/buildingregulations/ Construction Details:
approveddocuments/partl/approved http://www.gov.scot/Topics/Built-Environment/
Building/Building-standards/publications/pubtech
Building Regulations Part F (2010): Ventilation
http://www.planningportal.gov.uk/buildingregulations/ British Fenestration Rating Council
approveddocuments/partf http://www.bfrc.org/

Domestic Building Services Compliance Guide

http://www.planningportal.gov.uk/buildingregulations/
approveddocuments/partl/compliance

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NOTES

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NOTES

24 SAP UNTANGLED | ZERO CARBON HUB

NOTE: This Guide is not a legal document and does
not form part of a Building Regulations approved
specification. It is for information and good practice
purposes only. Consult your Building Control Officer
for details on approved specification’s and policy.

Published February 2016, version 1.0

Copyright © 2016 Zero Carbon Hub

Please contact Zero Carbon Hub if you wish to

reproduce, publish or electronically store any part
of this document
Zero Carbon Hub
Layden House
76-86 Turnmill Street
London EC1M 5LG

T. 0845 888 7620

E. info@zerocarbonhub.org
www.zerocarbonhub.org