What is SAP?
SAP is the Government's Standard Assessment Procedure for Energy Rating of Dwellings and is used to demonstrate the compliance for dwellings with Part L of the Building Regulations and to provide energy ratings.
It is the Department for Business, Energy and Industrial Strategy (BEIS) methodology for assessing and comparing the energy and environmental performance of dwellings. Its purpose is to provide accurate and reliable assessments of dwelling energy performances that are needed to underpin energy and environmental policy initiatives.
It is used to underpin the delivery of a number of key energy and environmental initiatives such as:
- Building Regulations
- Zero carbon homes stamp duty exemptions
- Code for Sustainable Homes
- Energy Performance Certificates
- General housing stock analysis
How does ventilation fit into SAP?
A part of the SAP calculation process, the energy balance of a dwelling is taken into consideration and its calculation takes into account a range of factors that influence energy efficiency. They include:
- Materials used for construction of the dwelling.
- Thermal insulation of the building fabric.
- Ventilation characteristics of the dwelling and ventilation equipment.
- Efficiency and control of heating system(s).
- Solar gains through opening windows.
- The fuel and power used to provide space and water heating, ventilation and lighting.
- District heating services providing heat and hot water to the dwelling.
How does a SAP Assessment work?
SAP works by assessing how much energy a dwelling will consume and how much carbon dioxide (CO2) will be emitted in delivering a defined level of comfort and service provision and this is based on standardised occupancy conditions.
The principal steps in undertaking a SAP calculation are as follows:
1. Determine the overall dwelling dimensions
2. Calculate the rate of ventilation
3. Calculate the heat losses
4. Calculate the water heating energy requirements
5. Determine the internal gains
6. Determine the solar gains
7. Determine the mean internal temperature
8. Determine the degree days
9. Calculate the useful space heating requirement and then the delivered energy for this and for water heating.
10. Determine the fuel costs from the delivered energy figures.
11. Calculate the SAP rating.
12. Calculate the carbon dioxide emissions.
Product Characteristics Database (PCDB)
The PCDB is a database of ventilation products tested and listed against their performance characteristics.
What Ventilation technologies are included in the PCDB?
Mechanical Extract Ventilation (MEV)
MEV is a fan driven ventilation system, which only extracts air from the dwelling. The SAP calculation is based on a throughput of 0.5 air changes per hour through the mechanical system, plus infiltration.
MEV can be either:
- Centralised: air is extracted from wet rooms via ducting and expelled by means of a central fan.
- Decentralised: air is extracted by continuously-running fans in each wet room.
Nuaire MEV systems recognised for use within SAP are:
- MEVDC, MEVDC2 and MEVDC-ES (Centralised)
- Genie-DCE and dMEV (Decentralised)
Balanced whole house mechanical ventilation
Balanced ventilation provides fresh air to habitable rooms in the dwelling and extracts stale air from wet rooms. Mechanical Ventilation with Heat Recovery (MVHR) is the product used in this category.
To find out more about MVHR, please visit our Residential Heat Recovery page.
Nuaire's MVHR products that are recognised for use in SAP are:
- MRXBOX95-WM1 and MRXBOX95AB-WM1
- MRXBOX95-WM2 and MRXBOX95AB-WM2
- MRXBOX95-WH1 and MRXBOX95AB-WH1