Area Weighted U-Value Calculator

Project Addess

Actual Extension

Net Area (m²)

U-value (w/m²k)

Heat Loss (W)

Proportion of Total

External Walls

-

Roof - Insulation at rafters

-

Roof - Flat Roof

-

Roof - Insulation at joists

-

Ground Floor

-

Windows

Roof Windows

Doors

Totals

-

Area weighted U-value

Notional Allowance Calculator

Floor Area of Extension

m²

25% of extension floor area

m²

Area of openings removed as a result of the extension

m²

Total Glazing Allowance

m²

Notional Extension

Net Area (m²)

U-value (w/m²k)

Heat Loss (W)

Proportion of Total

External Walls

-

Roof - Insulation at rafters

-

Roof - Flat Roof

-

Roof - Insulation at joists

-

Ground Floor

-

Windows

Roof Windows

Doors

Totals

-

Area weighted U-value

Compliance Results

Paragraph 10.7, AD Part L Vol.1 - 2021 (England)

External Wall u-value compliant?

Slope Roof u-value compliant?

Flat Roof u-value compliant?

Plane Roof u-value compliant?

Ground Floor u-value compliant?

Window u-value compliant?

Roof Window u-value compliant?

Door u-value compliant?

Paragraph 10.9, AD Part L Vol.1 - 2021 (England)

Actual area weighted u-value

Notional area weighted u-value

Compliance Achieved?

This online tool gives an indication of how an extension could comply using the Area Weighted U-Value Method Described in Building Regulations Part L 2021, 10.9.

Briary Energy supply this tool FOC to help homeowners and architects design buildings to comply with Part L.

We take no responsibility or liability for any errors or omissions in the content of this calculator. The information contained in this site is provided on an "as is" basis with no guarantees of completeness, accuracy, usefulness or timeliness.