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

0.28

-

Roof - Insulation at rafters

0.18

-

Roof - Flat Roof

0.18

-

Roof - Insulation at joists

0.16

-

Ground Floor

0.22

-

Windows

1.60

Roof Windows

1.60

Doors

1.80

Totals

-

Area weighted U-value

Compliance Results

Part 1 - Paragraph 4.1, AD L1B 2013 (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?

Part 2 - Paragraph 4.5, AD L1B 2013 (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 L1b.

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