SAP 2012 – What’s changed? (Thermal Bridging)

Up to 19 new linear thermal bridging junctions in the recently published SAP2012

SAP dictates how a dwelling will perform against the TER set by the standards, so picking out the changes from SAP2009 gives us a few pointers as regards dwelling performance under the next regulations.

  • A further 19 junctions have been added into SAP Appendix K (Most of them room in roof junctions or various junctions with external or party walls).
  • A few junctions approved and default values have been amended.
  • All references to confidence factors  have been removed (No competency or accreditation schemes available).
  • For some junctions there is no ‘approved’ value, so the default value will be required to be used unless a tested value is available.

Thermal bridging Image (roof junctions)

The new and amended junctions and values are outlined below:

 

Ref

Junction Detail

Approved value (W/mK)

Default value (W/mK)

Notes

Junctions with an external wall   

 

 

 

 

 

E5

Ground floor (normal)

0.16

0.32

Amended description

E19

Ground floor (inverted)

N/A

0.07

New junction

E20

Exposed floor (normal)

N/A

0.32

New junction

E21

Exposed floor (inverted)

N/A

0.32

New junction

E22

Basement floor

N/A

0.07

New junction

E23

Balcony (penetrates wall insulation)

N/A

1.00

New junction

E24

Eaves (insulation at ceiling level – inverted)

N/A

0.24

New junction

E18

Party wall between dwellings

0.03

0.06

Previously 0.06 / 0.12

E25

Staggered party wall between dwellings

N/A

0.06

New junction

Junctions with a party wall   

 

P6

Ground floor (inverted)

N/A

0.07

New junction

P2

Intermediate floor within a dwelling

N/A

0.00

Previously 0.00 / 0.04

P3

Intermediate floor between dwellings

N/A

0.00

Previously 0.00 / 0.04

P7

Exposed floor (normal)

N/A

0.16

New junction

P8

Exposed floor (inverted)

N/A

0.24

New junction

Junctions in roofs or room-in-roof   

 

 

 

 

 

R1

Head

N/A

0.08

New junction

R2

Sill

N/A

0.06

New junction

R3

Jamb

N/A

0.08

New junction

R4

Ridge (vaulted ceiling)

N/A

0.08

New junction

R5

Ridge (inverted)

N/A

0.04

New junction

R6

Flat ceiling

N/A

0.06

New junction

R7

Flat ceiling(inverted)

N/A

0.04

New junction

R8

Roof wall (rafter)

N/A

0.06

New junction

R9

Roof wall (flat ceiling)

N/A

0.04

New junction

With additional junctions now considered and additional heat losses added from those junctions, the designer will need to compensate elsewhere in the specification, as well as putting much more thought into how elements come together at junctions.

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About

Jon Ducker is a qualified energy assessor working for Kingspan Insulation Ltd. He has an extensive knowledge of energy efficiency, renewable energy systems and sustainability in buildings with an expert knowledge of the relevant sections of buildings regulations and standards and their interactions with SAP. He provides authoritative advice regarding energy assessments for a wide range of public and private sector clients.