SAP Part L Calculations and Examples

14, June, 2019 By yoke_admin Posted in

At Base Energy we can help design and assess your development to meet SAP / SBEM Part L 2013 compliance and we can help guide your development providing various cost effective solutions.

The new Part L 2013 is stricter than ever and harder to comply. You can’t just install solar PV panels and pass your SAP calculation. The fabric elements play a key part in the design and assessment of new buildings and if designed correctly will pass the building energy calculation. If you do not design it correctly from the outset, you will find it difficult to pass the SAP calculation at the end.

It is likely your project will need to exceed the minimum u-values* set out by Part L 2013, with their being a Fabric Compliance target. This is alongside the CO2 emission target, and the fabric compliance takes into account, u-values, air tightness, thermal bridging and thermal mass.

A SAP calculation is required for building regulations, Part L1a and Part L1b (existing). It is a heat loss calculation; working out the fuel cost of the dwelling and the CO2 emissions.

See below for an idea of the type of specifications needed to pass a Part L 2013 SAP calculation, based on some of our most common house types:

Standard Semi Detached House, 40sqm (Improved Fabric/Low Air Tightness Option)

Elements	Improvement	How to Achieve Compliance
Thermal Mass	Low Thermal Mass	Timber or Lightweight block
External Wall	Meet U-value of 0.24 W/m2k	100mm Crown Dritherm 32
Ground Floor	Meet U-value of 0.16 W/m2k	100mm Insulation Board
Roof	Meet U-value of 0.11 W/m2k	400mm Mineral Wool
Windows	Meet U-value of 1.3 W/m2k	Double Glazed, Argon Filled
Air Tightness	ATT of 4 m2/hm3 (@50Pa)	Seal Junctions Correctly
Thermal Bridging	Achieve Standard y-value (0.08)	Follow ACD Guidelines
Thermal Bridging Lintels	Lintel Psi Value (0.05)	Keystone Hi Lintels
Heating Controls	Install Improved Heating Controls	Timer and Temperature Zone, Weather Comp

Standard Semi Detached House, 40sqm (Renewables Option)

Elements	Improvement	How to Achieve Compliance
Thermal Mass	Medium Thermal Mass	Medium to Dense block
External Wall	Meet U-value of 0.26 W/m2k	100mm Crown Dritherm 32
Ground Floor	Meet U-value of 0.18 W/m2k	85mm Insulation Board
Roof	Meet U-value of 0.13 W/m2k	350mm Mineral Wool
Windows	Meet U-value of 1.4 W/m2k	Double Glazed, Argon Filled
Air Tightness	ATT of 5 m2/hm3 (@50Pa)	Seal Junctions Correctly
Thermal Bridging	Achieve Standard y-value (0.08)	Follow ACD Guidelines
Heating Controls	Install Improved Heating Controls	Timer and Temperature Zone Control
Renewables/Extra Features	Photovoltaic Panels	Approx. 0.5 kWp, South Facing

Standard Semi Detached House, 40sqm (Mechanical Ventilation Option)

Elements	Improvement	How to Achieve Compliance
Thermal Mass	Low Thermal Mass	Timber or Lightweight block
External Wall	Meet U-value of 0.24 W/m2k	100mm Crown Dritherm 32
Ground Floor	Meet U-value of 0.16 W/m2k	100mm Insulation Board
Roof	Meet U-value of 0.11 W/m2k	400mm Mineral Wool
Windows	Meet U-value of 1.3 W/m2k	Double Glazed, Argon Filled
Air Tightness	ATT of 5 m2/hm3 (@50Pa)	Seal Junctions Correctly
Thermal Bridging	Achieve Standard y-value (0.08)	Follow ACD Guidelines
Heating Controls	Install Improved Heating Controls	Timer and Temperature Zone Control
Renewables/Extra Features	Efficient Ventilation System	Mechanical Ventilation Heat Recovery

Large Detached House, 150sqm (Improved Fabric/Lower Air Tightness Option)

Elements	Improvement	How to Achieve
External Wall	Meet U-value of 0.18 W/m2k	150mm Crown Dritherm 32
Ground Floor	Meet U-value of 0.12 W/m2k	125mm Insulation Board
Roof	Meet U-value of 0.1 W/m2k	450mm Mineral Wool
Windows	Meet U-value of 1.4 W/m2k	Double Glazed, Argon Filled
Air Tightness	ATT of 7 m2/hm3 (@50Pa)	Seal Junctions Correctly
Thermal Bridging	Achieve Standard y-value (0.08)	Follow ACD Guidlines
Heating Controls	Install Improved Heating Controls	Timer and Temperature Zone Control
Renewables/Extra Features	N/A	N/A

Large Detached House, 150sqm (Standard Option)

Elements	Improvement	How to Achieve
External Wall	Meet U-value of 0.21 W/m2k	75mm Insulation Board
Ground Floor	Meet U-value of 0.16W/m2k	100mm Insulation Board
Roof	Meet U-value of 0.1 W/m2k	450mm Mineral Wool
Windows	Meet U-value of 1.3 W/m2k	Double Glazed, Argon Filled
Air Tightness	ATT of 5 m2/hm3 (@50Pa)	Seal Junctions Correctly
Thermal Bridging	Achieve Standard y-value (0.08)	Follow ACD Guidelines
Thermal Bridging Lintels	Lintel Psi Value (0.05)	Keystone Hi Lintels
Heating Controls	Install Improved Heating Controls	Time and Temperature Zone, Weather comp
Renewables/Extra Features	N/A	N/A

Large Detached House, 150sqm (Renewables Option)

Elements	Improvement	How to Achieve Compliance
External Wall	Meet U-value of 0.21 W/m2k	75mm Insulation Board
Ground Floor	Meet U-value of 0.17 W/m2k	85mm Insulation Board
Roof	Meet U-value of 0.11 W/m2k	400mm Mineral Wool
Windows	Meet U-value of 1.4 W/m2k	Double Glazed, Argon Filled
Air Tightness	ATT of 6 m2/hm3 (@50Pa)	Seal Junctions Correctly
Thermal Bridging	Achieve Standard y-value (0.08)	Follow ACD Guidelines
Heating Controls	Install Improved Heating Controls	Timer and Temperature Zone Control
Renewables/Extra Features	Photovoltaic Panels	Approx. 1 kWp, South Facing

Large Detached House, 150sqm (Mechanical Ventilation Option)

Elements	Improvement	How to Achieve Compliance
External Wall	Meet U-value of 0.21 W/m2k	75mm Insulation Board
Ground Floor	Meet U-value of 0.17 W/m2k	85mm Insulation Board
Roof	Meet U-value of 0.11 W/m2k	400mm Mineral Wool
Windows	Meet U-value of 1.4 W/m2k	Double Glazed, Argon Filled
Air Tightness	ATT of 4 m2/hm3 (@50Pa)	Seal Junctions Correctly
Thermal Bridging	Achieve Standard y-value (0.08)	Follow ACD Guidelines
Heating Controls	Install Improved Heating Controls	Timer and Temperature Zone Control
Renewables/Extra Features	Efficient Ventilation System	Mechanical Ventilation Heat Recovery

It is more difficult for larger houses to comply with the SAP assessment, and therefore require improved u-values and other energy efficient systems. The air tightness of larger houses is also more difficult to achieving low air test results.

There are many new products and materials available now which can be included in the SAP calculation. Such as improved heating controls, shower heat recovery, insulated lintels, thermal mass can actually have a big impact, with reduced heat demand and therefore makes it easier to comply.