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Extension – Highly Glazed Extension Report

SAP Calculations - EPC's - Air Permeability Testing - Water Calculations - Ventilation Testing

Energy Compliance Report

As specialists not generalists we only deal with Part L of the building regulations.

We take time to understand each project, not only on a technical level but also on a client level. We recognise that every client is unique requiring unique solutions to move their project forward. 

We stronlgly focus on communication and  managing our client’s expectations and guarantee we will always keep to (or beat) agreed time scales.

Notional & Proposed SAP Calculations

For “Highly Glazed Extensions”


Send us your plans

Send us the floor plans, sections, elevations and specifications of your new extension. Specifications should include details of floors, roofs, walls, windows and doors. Please also include any new primary or secondary heating that may be installed into the extension.


Your Existing Dwelling

We also require details of your existing dwelling. Preferably in plan form with specification details of heat loss floors, walls, roofs and openings . If you’re unable to supply plans and specifications please call for alternative ways we can do the calculations. We also need details of the primary heating system with associated controls, the hot water system with associated controls, any secondary heating, mechanical ventilation, fixed lighting and any renewables.


Part L Assessment

Calculations are done in conjunction with the ‘elemental recipe’ as defined in Appendix R of SAP2012. We model your proposed extension ‘against’ a notional extension of the same size but with 25% glazing and with all components being built to minimum allowable u-values.



Post Assessment

Once we’ve completed our assessment we will let you know if your extension is compliant. If it is great, if not we will advise you of the cheapest and least invasive way to achieve compliance.



You will receive a report that will demonstrate to your building control body that the CO2 emissions of your dwelling with the proposed extension are less than the CO2 emissions of your dwelling with the notional extension. subject to any additional specification or remedial improvements (if necessary). In essence this demonstrates Part L1b compliance.

Contact us

OFFICE: 01392 683664          MOBILE: 077968 46047        EMAIL: info@pecairsap.com


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Top Tips

HGE’s require SAP assessors to  show CO2 emissions from a proposed extension are equal to or better than an extension of the same size and constructed in accordance with the ‘elemental recipe’ as defined in Appendix R of SAP 2012 (the notional extension.)
Dimensions of the walls, floors and roofs for the proposed and notional extensions are identical (although the U-values of each element may vary.) The openings of the notional extension are modelled on the same orientations but are reduced in proportion so that the total of all the opening apertures are = to 25% of extension floor area. If the CO2 emissions from the proposed extension are less than those of the notional extension then compliance is achieved, if not consider the following: 
O If the extension is part of a bigger renovation, other upgrades made can be enough to compensate shortfalls i.e a new boiler.
O Upgrade fabric element heat loss specifications for the extension.
O Upgrade heat loss elements in the main house i.e add extra loft insulation.
O Add other CO2 efficiency products i.e a weather compensator.
O A good SAP assessor will have a myriad of solutions to ensure compliance is achieved.