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Accredited Construction Details

Accredited Construction Details (ACDs) have been developed to help the construction industry achieve the performance standards required to comply with the energy efficiency requirements (Part L) of the Building Regulations.

The details and introductory section of this document focus on the issues of insulation continuity (minimising cold bridging) and airtightness. They are not intended to provide any detailed guidance on other performance aspects such as vapour control and ventilation, which must also be considered by the design and construction team.

The details contain checklists which should be used by the designer, constructor and building control body to demonstrate compliance. The details have been grouped by generic construction type. It is strongly recommended that the introductory section ‘Accredited Construction Details’ is read in conjunction with the particular set of ACDs, in order to better understand the principles underpinning the details themselves.

Above information is from the Planning Portal website.

However since the 2010 & 2014 Part L changes have been in force the methods of achieving compliance have changed.

 

Please click our maps for SAP Calculations/SAP Ratings in your area.

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Accredited Construction Details 

Before the 2010 changes, it was commonly assumed that new dwellings followed the guidance for Accredited Construction Details which can be found on the Planning Portal website. In addition for a higher specification dwelling, designers would use guidance on the Energy Saving Trust website. These are known as Enhanced Construction Details.

Since the 2010 changes and more so the 2014 changes, Thermal modelling has been introduced as a way of achieving compliance along with the Planning Portal, Enhanced and manufacturers details.

The details that need to be justified under the new changes are as follows.

Came into force 6th April 2014 – Applicable to new dwellings application on or after that date.

External Wall Junctions Ref Junction Detail Accredited
Ψ (W/m·K)
Default
Ψ (W/m·K)
External Wall Junctions E1 Steel lintel with perforated steel base plate 0.50 1.00
External Wall Junctions E2 Other lintels (including other steel lintels) 0.30 1.00
External Wall Junctions E3 Sill 0.04 0.08
External Wall Junctions E4 Jamb 0.05 0.10
External Wall Junctions E5 Ground floor (normal) 0.16 0.32
External Wall Junctions E19 Ground floor (inverted) 0.07
External Wall Junctions E20 Exposed floor (normal) 0.32
External Wall Junctions E21 Exposed floor (inverted) 0.32
External Wall Junctions E22 Basement floor 0.07
External Wall Junctions E6 Intermediate floor within a dwelling 0.07 0.14
External Wall Junctions E7 Party floor between dwellings (in blocks of flats) a) 0.07 0.14
External Wall Junctions E8 Balcony within a dwelling, wall insulation continuous b) 0.00 0.00
External Wall Junctions E9 Balcony between dwellings, wall insulation continuous b) c) 0.02 0.04
External Wall Junctions E23 Balcony within or between dwellings, balcony support
penetrates wall insulation
1.00
External Wall Junctions E10 Eaves (insulation at ceiling level) 0.06 0.12
External Wall Junctions E24 Eaves (insulation at ceiling level - inverted) 0.24
External Wall Junctions E11 Eaves (insulation at rafter level) 0.04 0.08
External Wall Junctions E12 Gable (insulation at ceiling level) 0.24 0.48
External Wall Junctions E13 Gable (insulation at rafter level) 0.04 0.08
External Wall Junctions E14 Flat roof 0.08
External Wall Junctions E15 Flat roof with parapet 0.56
External Wall Junctions E16 Corner (normal) 0.09 0.18
External Wall Junctions E17 Corner (inverted – internal area greater than external area) -0.09 0.00
External Wall Junctions E18 Party wall between dwellings c) ..0.06 0.12
External Wall Junctions E25 Staggered party wall between dwellings c) 0.12

Junctions with party wall Ref Junction Detail Accredited
Ψ (W/m·K)
Default
Ψ (W/m·K)
Junctions with party wall P1 Ground floor 0.16
Junctions with party wall P6 Ground floor (inverted) 0.07
Junctions with party wall P6 Intermediate floor within a dwelling 0.00
Junctions with party wall P3 Intermediate floor between dwellings (in blocks of flats) 0.00
Junctions with party wall P7 Exposed floor (normal) 0.16
Junctions with party wall P8 Exposed floor (inverted) 0.24
Junctions with party wall P4 Roof (insulation at ceiling level) 0.24
Junctions with party wall P5 Roof (insulation at rafter level) 0.08

Junctions within a roof or with a room in roof Ref Junction Detail Accredited
Ψ (W/m·K)
Default
Ψ (W/m·K)
Junctions within a roof or with a room in roof R1 Head of roof window 0.08
Junctions within a roof or with a room in roof R2 Sill of roof window 0.06
Junctions within a roof or with a room in roof R3 Jamb of roof window 0.08
Junctions within a roof or with a room in roof R4 Ridge (vaulted ceiling) 0.08
Junctions within a roof or with a room in roof R5 Ridge (inverted) 0.04
Junctions within a roof or with a room in roof R6 Flat ceiling 0.06
Junctions within a roof or with a room in roof R7 Flat ceiling (inverted) 0.04
Junctions within a roof or with a room in roof R8 Roof to wall (rafter) 0.06
Junctions within a roof or with a room in roof R9 Roof to wall (flat ceiling) 0.04

Came into force 1st October –  Applicable to new dwellings application on or after that date.

External Wall Junctions Ref Junction Detail Accredited
Ψ (W/m·K)
Default
Ψ (W/m·K)
External Wall Junctions E1 Steel lintel with perforated steel base plate 0.50 1.00
External Wall Junctions E2 Other lintels (including other steel lintels) 0.30 1.00
External Wall Junctions E3 Sill 0.04 0.08
External Wall Junctions E4 Jamb 0.05 0.10
External Wall Junctions E5 Ground floor 0.16 0.32
External Wall Junctions E6 Intermediate floor within a dwelling 0.07 0.14
External Wall Junctions E7 Intermediate floor between dwellings (in blocks of flats) a) 0.07 0.14
External Wall Junctions E8 Balcony within a dwelling b) 0.00 0.00*
External Wall Junctions E9 Balcony between dwellings a) b) 0.02 0.04*
External Wall Junctions E10 Eaves (insulation at ceiling level) 0.06 0.12
External Wall Junctions E11 Eaves (insulation at rafter level) 0.04 0.08
External Wall Junctions E12 Gable (insulation at ceiling level) 0.24 0.48
External Wall Junctions E13 Gable (insulation at rafter level) 0.04 0.08
External Wall Junctions E14 Flat roof 0.04 0.08
External Wall Junctions E15 Flat roof with parapet 0.28 0.56
External Wall Junctions E16 Corner (normal) 0.09 0.18
External Wall Junctions E17 Corner (inverted – internal area greater than external area) -0.09 0.00
External Wall Junctions E18 Party wall between dwellings a) 0.06 0.12
Junctions with a Party Wall a) P1 Ground floor 0.08 0.16
Junctions with a Party Wall a) P2 Intermediate floor within a dwelling 0.00 0.04
Junctions with a Party Wall a) P3 Intermediate floor between dwellings (in blocks of flats) 0.00 0.04
Junctions with a Party Wall a) P4 Roof (insulation at ceiling level) 0.12 0.24
Junctions with a Party Wall a) P5 Roof (insulation at rafter level) 0.02 0.04

Click the links to the below to see typical junction details. The Accredited Ψ values in the above table are from the Planning Portal website. These are standard details that apply to a lot of typical construction. The Enhanced details link will take take you to the Energy Saving Trust website and are a higher spec of details but help the DER/TER calculations a great deal.

Planning Portal Details

Enhanced Construction details

 

a) Value of Ψ is applied to each dwelling
b) This is an externally supported balcony (the balcony slab is not a continuation of the floor
slab) where the wall insulation is continuous and not bridged by the balcony slab
* Value valid only if balcony support does not penetrate the wall insulation. If it does so
penetrate, either a Y-value must be calculated for the junction, or the SAP calculation uses
the default overall thermal bridging of y = 0.15

 

 

Please Contact us for information on Accredited Construction Details
.


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