SAP and Part L calculations from £225
Building control wants proof that a new home or conversion meets the energy standard. We coordinate the calculation with an accredited assessor, so it matches the drawings you submit.
£225 fixed fee, no VAT to add
Prefer WhatsApp? Send us a message · +44 7592 201353
The short answer
SAP, the Standard Assessment Procedure, is the method used to calculate the energy performance of a dwelling for Part L of the Building Regulations. The calculation is carried out by an accredited assessor, and we coordinate it with your drawings. Our fee is £225, no VAT to add.
SAP and Part L calculations
from £225
- Fixed fee
- £225
- VAT
- None to add
- Briefing the accredited assessor from your drawings, so the model matches what will be built
- A design-stage SAP calculation and the resulting energy performance figures
- A specification note of the fabric, glazing, heating and ventilation the calculation assumes
- Changes to the drawings or specification where the first run does not pass
- The calculation in a form you can send to building control with the application
- Coordination with the as-built stage, so the final calculation matches the finished work
£225. A starting fee: we confirm one fixed figure after checking your address. The council’s own fee, where there is one, is paid to the council.
Get my fixed feeHow the calculation runs
Design drawings
We send the assessor the plans, sections and the proposed construction.
Specification
Walls, roof, floor, windows, heating and ventilation are specified together.
First run
The assessor models the dwelling and compares it with the notional dwelling.
Adjust
If it does not pass, we change the specification, such as insulation or glazing, until it does.
Submit and complete
The design-stage result goes to building control and the as-built figures follow.
What SAP checks, in plain terms
A new dwelling must meet a minimum standard of total energy performance, assessed by comparing the actual dwelling with a theoretical notional dwelling of the same size and shape, with standardised fabric and services. The comparison must be made both at the design stage and when the work is complete, according to Approved Document L.
The notional dwelling’s properties are defined in SAP itself. So the specification you choose, such as a heat pump or gas boiler and the amount of glazing, can pass or fail the same house.
The limits behind the model
For a new dwelling, the limiting U-values are 0.16 for roofs, 0.26 for walls, 0.18 for floors and 1.6 for windows, in watts per square metre kelvin, with an air permeability limit of 8.0 cubic metres per hour per square metre at 50 pascals. These are backstops: the calculation can fail even when each element meets its limit.
Where a new element is added to an existing dwelling, such as an extension wall, the limits are tighter for walls and roofs: 0.18 and 0.15 respectively. Whether an extension needs a full SAP calculation depends on the building control body and the size of the extension, and we tell you before you pay.
- New dwelling limits: roof 0.16, wall 0.26, floor 0.18, window 1.6
- Air permeability at most 8.0 m³/(h·m²) at 50 Pa
- New wall in an existing dwelling: 0.18; new roof: 0.15
Design stage and as-built
The first calculation is on the design. A second, as-built calculation records what was actually installed, and a new dwelling must also be pressure-tested, as Regulation 43 requires. The two must agree, so the specification cannot drift on site without someone re-running the numbers.
We pass the as-built details to the assessor at completion, so the certificate that building control and a buyer will want matches the house.
Energy rules in numbers
0.16
Maximum U-value, in W/m²K, for any roof of a new dwelling.
Source: Approved Document L volume 1: conservation of fuel and power, dwellings (GOV.UK)
0.26
Maximum U-value, in W/m²K, for a wall of a new dwelling.
Source: Approved Document L volume 1: conservation of fuel and power, dwellings (GOV.UK)
1.6
Maximum U-value, in W/m²K, for a window of a new dwelling.
Source: Approved Document L volume 1: conservation of fuel and power, dwellings (GOV.UK)
8.0
Maximum air permeability, in m³/(h·m²) at 50 Pa, for a new dwelling.
Source: Approved Document L volume 1: conservation of fuel and power, dwellings (GOV.UK)
0.18
Maximum U-value, in W/m²K, for a new wall in an existing dwelling.
Source: Approved Document L volume 1: conservation of fuel and power, dwellings (GOV.UK)
0.15
Maximum U-value, in W/m²K, for a new roof element in an existing dwelling.
Source: Approved Document L volume 1: conservation of fuel and power, dwellings (GOV.UK)
2 stages
A new dwelling’s energy performance is calculated at design stage and again when work is complete.
Source: Approved Document L volume 1: conservation of fuel and power, dwellings (GOV.UK)
Questions about SAP
Do I need SAP for an extension?
Not usually a full SAP. An extension normally needs the elements to meet the limiting U-values, and some projects need an energy calculation. Your building control body decides, and we check with it.
Who is the accredited assessor?
An independent energy assessor with the right accreditation, whom we instruct for you. We coordinate; the assessor signs the calculation.
What if the calculation fails?
We change the specification, for example the insulation, glazing or heating, and the assessor re-runs it. We change the drawings to match.
Is this the same as an EPC?
No. An energy performance certificate is issued for a completed building and uses SAP data, but the design-stage calculation is the one building control asks for.
Pass the energy test on paper first
Send the drawings or the address. We reply with the scope and a fixed fee of £225.