Modern House

Thermcalc Limited

Design Stage SAP Calculations

A SAP Data form will need to be completed showing the proposed design specifications for each dwelling and along with a set of plan, section & elevation drawings in PDF format. These can then be e-mailed to

Final As Built SAP Calculation and EPC
A completed final SAP and EPC checklist is required in order to provide the final as built SAP calculation and EPC & e-mailed  to
Information required on the checklist plus additional documentation is as follows:

1. Design stage job ref no. J_____
2. Royal Mail post addresses and to which plot that they apply.
3. Make, model of boiler, heat pump etc and hot water storage tank size if applicable.
4. Confirm kilowatt rating of any photovoltaic arrays, size and make of evacuated tube or flat
plate collectors.
5. Please supply MCS certificates for renewable energies, proof of glazing U-Values and an
air pressure test certificate if applicable.
6. Any changes to the original design stage SAP calculation if applicable.
7. Sign, date and supply e-mail address at the bottom of the form.

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Fees (From 1st January 2021)

Total Floor Area up to 300m2 the fee will be £95.00 + VAT
Total Floor Area between 300m2 and 400m2 the fee will be £125.00 + VAT
Total Floor Area between 400m2 and over the fee will be £165.00 + VAT
Final As Built Calculations including EPC document the fee will be £65.00 + VAT
(Please Note that the final SAP & EPC fee is for design stage work was previously carried by Thermcalc Limited. If not

the design stage calculation fee will be payable in addition to this)
Duplicate dwelling calculations £50.00 + VAT
Amendments the fee will be £50.00 + VAT
All SAP calculations and EPC´s will be E-mailed to
clients in PDF format only.
Please note that due to new Government legislation, final SAP calculations & EPCs can only be provided once the EPC checklist & relevant other documentation such as air test certificates & MCS cerrtificates are received.

Modern House
L1A Regulations - SAP 2012

Most of the changes in Part L 2013 focus on residential new build, which makes
sense considering that the zero carbon target is only 2 years away. There is 6%
uplift in the Target Emissions Rating (TER) on 2010 levels. This is slightly lower
than the 8% target originally put forward as the Government’s preferred option
when it consulted in 2012, the reasoning being that “it was difficult for detached
houses to achieve the 8% target through fabric measures only, on basis of cost
effectiveness and consistency of construction.”
The most significant difference between 2010 and 2013 Building Regulations is
the introduction of Target Fabric Energy Efficiency (TFEE) and Dwelling Fabric
Energy Efficiency (DFEE). These are measured in kWh/m2/yr and practitioners
will need to learn to use them a lot in the short-term future. For a dwelling to
comply with Criterion 1, the DER must be less than the TER and the DFEE less
than the TFEE. So, what is the TFEE and how is this calculated? The TFEE is
approximately equal to the Interim FEES (Fabric Energy Efficiency Scheme) level,
as defined by Zero Carbon Hub a couple of years ago.
Another new element within Part L 2013 is the introduction of the Elemental
Recipe. This recipe includes a performance specification for the building fabric
and services, which is compliant with Criterion 2 and if it is followed by the design
team should achieve compliance in almost all dwellings for Criterion 1. [1] This
recipe will give a compliant DER and a compliant DFEE (as the TFEE is
calculated by increasing the kWh/m2/yr of the elemental recipe by 15%). This
doesn’t mean that all buildings need to be designed in line with the recipe.
Developers and the design team can always decide to follow a different
specification if their approach still meets the TER and TFEE.


Thermcalc Limited

(Accredited On Construction Energy Assessor)

Quidos QUID207582

1 The Landway, Borough Green, Sevenoaks, Kent, TN15 8RG.

Tel: 01732 886195   E-Mail:



Thermcalc will only produce calculations for new build dwellings & conversions into
dwellings from existing buildings. Calculations will not be carried out for commercial
buildings or house extensions. Please note that accredited construction & Y-Value
calculations are not provided by Thermcalc Ltd but can be included in your
calculations if provided by a third party.

Thermcalc Limited

General Information

To avoid using renewable energy in your house design, low U-Values, good primary heating
and a low air pressure test result may do the trick. (See design example below). Note that
this does not work in every case, so a heat pump or solar panel array maybe required to
help you gain a pass. (Note that the use of an air source or ground source heat pump for
the primary heating will make getting a pass in your calculations a much easier task,
generally no accredited details will be required and possibly avoiding an air test where sites
have 2 or less dwellings for the project)
Example of Low U-Values for Guidance Only
Floor = 0.10
Walls = 0.18
Roofs = 0.13
Accredited detail construction not required Y= 0.15.
Gas boiler with 89% SEDBUK rating
Weather compensator added to boiler
Primary Heating Controls - Use time temperature zone control.
Secondary heating such as a HETAS approved log burner or open fire

Party walls The following u-values are specified in the SAP calculation:
Solid. Wall u-value = 0.0
Unfilled cavity with no effective edge sealing. Wall U-value = 0.5.
Unfilled cavity with effective sealing around all exposed edges and in line with insulation layers in abutting elements. Wall U-Value = 0.2.


L1A Construction Examples 

(SAP & EPC Forms Download at The Bottom of The Page)

For Guidance Purposes Only

Ground Floor
Beam/Celcon Std/150mm Celotex XR4000/Screed (Note that ground floor U-values vary
dependant upon the perimeter & area of the floor)
Sheltered Floors
e.g. floor between dwelling & garage > (250mm Mineral wool laid between joists)
Block Type
Aircrete blocks e.g Celcon, Thermalite and Durox. These blocks give an improved Thermal
Mass Parameter (TMP) in your calculations which improves the SAP rating.
Walls Fully Filled Cavity
Brick/100mm Xtratherm Full Fill CavityTherm CT/PIR (includes 5mm unvented airspace) /100mm
Celcon Standard/12.5mm P´bd on dabs. U-Value = 0.18
Brick/100mm Dritherm 32/100mm Celcon Standard/52.5mm Celotex PL4000. U-Value = 0.18

Brick/10mm Low-E Residual Cavity/90mm Kingspan K106/100mm Celcom Std/12.5mm P'bd on dabs

Walls Partially Filled Cavity

Brick/50mm Low-E Cavity/75mm Celotex CW4000/100 Celcon Std/12.5 P'bd ondads. U-Value = 0.20

Cold Roof

400mm Mineral Wool (K=0.04) Cross Laid . U-Value = 0.10

Sloping Roof -bUnVented With Breather Membrane

120mm Celotex XR4000 Between Rafters/52.5mm Celotex PL4000 Under Rafters. U-Value = 0.15

Flat Roof

130mm Celotex EL3000 Over Joists. U-Value = 0.17


Redfan Solutions

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Standard Assessment Procedure (SAP)


Contact Us

1 The Landway, Borough Green, Sevenoaks

TN15 8RG, UK

Thermcalc Limited

Telephone: 01732 886195

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