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SAP Calculations for Conversions
Part L compliant SAP Calculations for conversions and change of use projects, completed by Elmhurst accredited assessors. Fast turnaround for clients nationwide.
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What Is a SAP Calculation for Conversions?
A SAP calculation for a conversion is an energy assessment used to show that a change of use project will meet the Part L energy efficiency standards. Conversions are treated differently to new build homes; there is no overall carbon or primary energy target to hit, but Building Control still need clear evidence that the fabric and services are reasonable for the new dwelling created.
Under Approved Document L, compliance for conversions can be shown in two ways. The first is an elemental approach using limiting U-values for new thermal elements and minimum efficiencies for building services. The second is to use a SAP conversion calculation to demonstrate that the dwelling has acceptable primary energy, carbon emissions and fabric performance. We specialise in the SAP route and can also help you check U-values against the standards in AD L.
The SAP conversion calculation looks at the existing structure, any new or upgraded walls, floors and roofs, the glazing and doors, and the heating, hot water and ventilation systems serving the finished dwelling. We make sure new thermal elements meet the limiting U-values for existing dwellings and that the overall conversion is reasonable and compliant for Building Control. Even where compliance is signed off using the elemental method, a SAP EPC will still be required if the dwelling is to be sold or let, and we can provide this at the As-Built stage.
Our conversion SAP service builds on the same approach used in our main SAP Calculations for dwellings, but is tailored to the specific rules for material changes of use and conversions under Part L.
Which Types of Conversions Need a SAP Calculation?
Conversion SAP calculations are commonly needed for a wide range of change of use projects. If you are turning an existing building into one or more homes, it is very likely that a SAP conversion calculation will be required for Building Control sign off.
- Garage conversions to habitable rooms - where an attached or detached garage becomes a living space, annexe or separate dwelling.
- Barn and agricultural building conversions - barn conversion SAP calculations check new thermal elements, glazing and heating so that rural homes meet current Part L standards.
- Commercial to residential conversions - shops, offices and other commercial buildings converted into flats or houses usually need a SAP for each new dwelling created.
- Loft conversions forming new dwellings - some loft conversions that create a new self-contained dwelling or flat will require a SAP calculation for conversion.
- Outbuildings and annexes - outbuildings and annexes that become separate homes or long-term living spaces can fall under SAP for conversion and change of use.
If you are unsure whether your project needs a SAP calculation for conversion, send us your drawings and a brief description of the work. We will review the plans and confirm what is required for Part L compliance before you commit to any fees.
What Is Included in Our Conversion SAP Service
Our SAP service for conversions and change of use projects is designed to give clear answers when the rules can feel confusing. We assess the existing building, your proposed upgrades and the new services to help you achieve a comfortable and compliant dwelling.
- SAP conversion calculations for garages, barns, commercial buildings, lofts and annexes.
- Assessment of existing elements and new thermal elements including walls, floors and roofs, with checks against the limiting U-values for existing dwellings in Part L (for example 0.18 W/m²K for walls and floors, 0.15 W/m²K for roofs).
- Review of glazing, doors and roof lights to check overall heat loss and solar gains.
- Heating, hot water and ventilation system checks against Building Regulations requirements.
- Clear pass or fail summary with practical recommendations where improvements are needed.
- Reasonable design stage revisions included so you can refine insulation levels and system choices.
- As-Built SAP and EPC at completion as an optional add-on.
- Email support for your architect, builder and Building Control officer throughout the project.
Pricing for Conversion SAP Calculations
SAP Calculations for conversions are priced per dwelling with fixed, transparent fees. The cost depends on the type and complexity of the conversion, for example a simple garage conversion SAP will usually be cheaper than a large barn or commercial to residential conversion.
Standard Conversion SAP
From £200 per dwelling for straightforward conversion SAP calculations where the building layout and specification are simple.
Complex or Barn Conversions
From £250 to £300 for larger or more complex conversion SAP projects such as barn conversions and commercial to residential schemes.
As-Built SAP + EPC
Reduced fee add-on for As-Built SAP and EPC where we have already completed the design stage conversion SAP for your project.
How the Conversion SAP Process Works
The SAP process for conversions is straightforward. We focus on giving clear advice so that you, your architect and your builder can keep the project moving without delays from Building Control.
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Send us your conversion drawings and details
Upload your floor plans, elevations, sections and site plan along with any details you have on existing and proposed construction, windows and doors, heating and ventilation. If anything is missing we will let you know before we start the conversion SAP calculation.
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We complete your SAP conversion model
We build a SAP conversion calculation that reflects the existing building and your proposed upgrades. We check new thermal elements, glazing and services against the relevant Part L requirements and provide clear recommendations
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You receive your SAP report for Building Control
Once the SAP for conversion meets the required standards, we issue your design stage SAP report and Part L documentation. These can be sent straight to Building Control so that your conversion can proceed without hold ups.
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As-Built SAP and EPC at completion
When the conversion is finished we can update the SAP with the final specification, air test results and photographic evidence. We then provide the As-Built SAP and lodge the EPC for the new dwelling or dwellings.
Most conversion SAP calculations are completed within two to three working days once we have the information we need. If you have a tight Building Control deadline, let us know and we will confirm what is achievable.
What We Need for a Conversion SAP Calculation
Conversions and change of use projects often start from imperfect information. We work with what you have and help you fill in the gaps so that the SAP calculation for your conversion is both realistic and compliant.
- Floor plans with dimensions and room labels for the existing building and proposed layout.
- Elevations and sections showing existing and proposed openings, floor levels and roof form.
- A site plan showing orientation, access and any attached or adjacent buildings.
- Details of existing construction where known, for example wall, floor and roof build ups.
- Proposed insulation upgrades to new thermal elements and any upgraded existing elements.
- Window and door schedule with sizes, types and U-values if available.
- Heating and hot water system specification, including boiler or heat pump models and controls.
- Ventilation information, such as extractor fans, dMEV, MEV or MVHR systems.
- Any proposed renewable technologies, such as solar PV or connection to a low carbon heat network.
If you are unsure about any of these details, we can work from reasonable assumptions and update the SAP as the design is refined. We will always highlight assumptions so that you and your builder can decide where upgrades will have the greatest benefit.
For conversions there is no requirement for airtightness testing under Part L; if no test is carried out we will normally use the standard SAP default of 15 m³/m²·h @ 50Pa, or we can enter a measured test result if you have one.
Why Choose Us for Conversion SAP Calculations
Conversion projects rarely fit a standard pattern. You need a SAP assessor who understands how to balance existing construction, new thermal elements and modern services so that the finished dwelling meets Part L without unnecessary cost. That is the focus of our conversion SAP service.
- Elmhurst accredited OCDEA with experience in a wide range of conversion and change of use projects.
- SAP conversion calculations for garage, barn, commercial to residential, loft and annexe projects.
- Fixed, transparent pricing with no hidden extras or rush fees.
- Fast turnaround times and clear communication throughout.
- Practical recommendations that work on real sites, not just on paper.
- Design stage and As-Built services so you can use a single assessor from start to finish.
- Reports written in clear language that Building Control officers can follow with ease.
Conversion SAP Frequently Asked Questions
Does my conversion need a SAP calculation?
A SAP calculation for a conversion is normally required when a building that was not a dwelling becomes one, or when you create a new self-contained flat. This includes barn conversions, commercial to residential projects and some garage and loft conversions. If you are unsure whether your conversion needs a SAP calculation, send us your plans and we will confirm this for free.
What drawings do I need to send for a conversion SAP?
For a conversion SAP calculation we need floor plans, elevations, sections, a site plan, details of existing and proposed construction, and a window and door schedule. Heating and hot water specification, ventilation details and any planned insulation upgrades or renewables are also helpful.
What are new thermal elements in a conversion?
New thermal elements are new or significantly upgraded walls, floors and roofs that separate the dwelling from the outside or from unheated spaces. In a conversion SAP we assess these new thermal elements to make sure they meet the U-value limits in Part L and that the overall conversion meets the Building Regulations requirements.
Do all loft conversions need a SAP calculation?
Not every loft conversion needs a SAP calculation. A SAP conversion calculation is usually required where a loft is being turned into a separate dwelling or flat, or where there are significant changes to the thermal envelope. If your loft conversion is part of a change of use or you are unsure, send through your plans and we will advise.
What happens if my conversion fails the SAP calculation?
If your SAP conversion calculation does not meet the Part L targets we will explain the reasons and provide a clear list of improvements. This may include better insulation to new thermal elements, improved glazing, changes to the heating system or the addition of renewables. We will work with you until the conversion passes.
Do you provide the EPC at completion?
Yes. Once the conversion is complete we can produce an As-Built SAP and lodge the EPC for the new dwelling or dwellings. If we have already completed the design stage SAP for your conversion, the As-Built SAP and EPC are available as a reduced price upgrade.
Will Building Control accept your SAP conversion reports?
Yes. All of our SAP conversion calculations are completed by an Elmhurst accredited OCDEA using approved software. Our design stage and As-Built reports are suitable for submission to Building Control and are accepted across the UK.
Ready to get your SAP Calculation?
All SAP calculations completed by an Elmhurst-accredited OCDEA and accepted by Building Control nationwide.