New Build Info: Sap Assessments & Notional / Limiting U-Values

This page provides essential information when using our New Build Specifications.

In particular, please see the point below regarding SAP Calculations** & Starting / Limiting / Notional Values.

New Builds are a specialist area and should only be undertaken by competent, qualified and experienced professionals requiring the services of a professional architect who can approve all surveys, investigations and oversee employment of other professional services.

The specifications only apply to dwellings up to 2 storeys, with some specifications additionally applicable to 3 storeys.

The design and construction of the proposed works is always the responsibility of the designer, applicant and contractor.

When using our Specifications, checks should be made to ensure that they apply to your specific proposed works.

Additional Factors requiring attention for New Builds

In order to create a Complete Building Regs Specification, additional factors will need to be covered.

This should include:

• SAP Calculations**. Important Note: When using the New Build Specs and Detail Drawings, some will require modification according to your SAP assessment as many of the values provided are Starting Values***. In general, these will need to be adjusted for each project (and probably won't be accepted with the existing values).

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  Notional / Limiting U-Values in SAP Assessment

  Within the New Build Specifications, for Walls, Floors, Roofs, Windows and Doors we provide 2 sets of Specifications with corresponding U-Values:

  • Notional U-Values
  • Limiting U-Values

  Notional U-Values (Wales: Elemental)

  During a SAP Assessment, the Actual Dwelling is compared to a 'Notional Dwelling' which uses the standard Notional U-Values. Choosing lower U-Values closer to the Notional U-Values should help meeting the SAP requirements for the Building Fabric as well as for other SAP requirements.

  It may not be necessary to use Notional U-Values for all elements but the minimum Building Fabric requirements will need to be met.

  Notional values [expressed in W/(m2⋅K)] for specific elements in New Dwellings are:

  England

  • External Walls: 0.18
  • Floors: 0.13
  • Roofs: 0.11
  • Opaque Doors (< 30% glazed area): 1.0
  • Semi-glazed Doors (30-60% glazed area): 1.0
  • Windows & Glazed Doors (> 60% glazed area): 1.2

  Wales (Elemental)

  • External Walls: 0.13 (Corridors: 0.18)
  • Floors: 0.11
  • Roofs: 0.11
  • Opaque Doors (< 30% glazed area): 1.0
  • Semi-glazed Doors (30-60% glazed area): 1.0
  • Windows & Glazed Doors (> 60% glazed area): 1.3

  Limiting U-Values (Wales: Worst-Acceptable)

  The Limiting U-Values are the worst-acceptable U-Values for individual elements.

  It may be possible to use Limiting U-Values for one or more elements in a New Build but doing so would generally mean that other elements would need lower/better U-Values, particularly in relation meeting the requirements for the Building Fabric.

  Limiting values [expressed in W/(m2⋅K)] for specific elements in New Dwellings are:

  England

  • External Walls: 0.26
  • Floors: 0.18
  • Roofs: 0.16
  • Doors (including glazed doors): 1.6
  • Windows: 1.6

  Wales (Worst-Acceptable)

  • External Walls Houses: 0.18 | External Walls Flats: 0.21
  • Floors: 0.15
  • Roofs: 0.13
  • Doors (including glazed doors): 1.4
  • Windows: 1.4

  There may also the option for using U-Values between the Limiting and Notional U-Values. We provide a U-Value Filter (currently for registered users) on the website which can be used to select specifications/drawings with alternative U-Values. However, care should be taken in choosing a specification/drawing that is correct for the specific application.

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  SAP Assessments for Domestic New Builds

  BuildingRegs4Plans provide a SAP Assessment Service for Domestic New Builds

  More information here

  

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