Criterion 1, 2 & 3

The DER and TER values are obtained from the simulated carbon dioxide emissions of two dwellings.

The ‘actual building’, which forms the basis of the DER calculation, is the building as designed, but subject to standard settings for secondary heating and lighting. Refer to L1A paragraphs 25 to 29 for further guidance. The DER calculation also must include, for final submission to Building Control, the measured air permeability.

The ‘notional building’, which forms the basis of the TER calculation, is a version of the actual building modified in accordance with rules relating to glazing area, insulation and system efficiency. These rules are defined in Appendix R of the SAP methodology^[5] document.

Both buildings have their carbon emissions calculated using the SAP methodology and the results of this are automatically fed into a compliance checklist; a template of which is provided by BRE.

It is important to note that the stipulation of standard input for L1 (2006) compliance calculations (DER & TER) means that calculation results as calculated for L1 (2006) will in general be different from those calculated for the ‘real’ building i.e. a ‘straight’ SAP calculation.

To obtain the TER, the CO2 emissions for the notional building are modified by certain factors as set out in the Design Standards section L1A.The purpose of these factors is to tighten the requirement on the actual building so that its performance exceeds that of the notional building. By this means the 2006 regulations impose a measurable degree of improvement over the standards applied in the 2002 regulations.

 

Criterion 2 imposes constraints on U-values and other aspects of building and system performance.

Maximum and mean U-values for different classes of construction must not exceed stated values. The software applies checks for compliance with this requirement before performing the actual and notional building simulations.

Conditions are also laid down in the following areas (see L1A section headed Design limits for fixed building services):

Heating and hot water service systems

Mechanical cooling

Mechanical ventilation systems

Insulation of pipes, ducts and vessels

Lighting (Internal & External)

 

This criterion is aimed at controlling summertime temperatures in dwellings. The key provisions are set out in L1A paragraph 46 and 47:

46  … provision should be made to limit internal temperature rise due to solar gains. This can be done by an appropriate combination of window size and orientation, solar protection through shading and other solar control measures, ventilation (day and night) and high thermal capacity…

47  SAP 2005 Appendix P contains a procedure enabling designers to check whether solar gains are excessive. Reasonable provision would be achieved if the SAP assessment indicates that the dwelling will not have a high risk of high internal temperatures.

The software provides an automated test by Appendix P.

L1 (2006) constitutes one of the Regulatory Frameworks covered by the <VE> Compliance view of the <Virtual Environment>. A brief summary of its features follows.

 

The <VE> Compliance view covers the following Regulatory Frameworks, which may be selected using the Regulatory Framework selector on the <VE> Compliance toolbar:

Part L1 (2006) – England/Wales/NI

Part L2 (2006) – ApacheSim method

Part L2 (2002) – England/Wales/NI

Section 6 (2004) – Scotland

Part L (2008) – Eire

These Regulatory Frameworks all share core features of the <VE> Compliance view, such as the model workspace, the browsers, the menus and the toolbars. For a description of these please consult the <VE> Compliance view User Guide.

 

Unlike L2 (2006) ApacheSim Regulatory Framework L1 (2006) does not produce a geometric model of the notional building. The notional building is handled purely numerically following the guidance of Appendix R of the SAP methodology document. 

Where there are unheated buffer spaces (including unheated roofs) in the actual building, the notional building treats these as heat loss paths for adjacent heated rooms (following the principles laid down in BS EN ISO 13789:1999 ^[2] ). For these adjacencies standard constructions are applied, replacing the heat loss paths (including the unheated spaces) in the actual building.

 

Data relating to individual rooms is entered via the Space Data tabs for the actual building. General Building Regulations data, such as the room ‘type’, is specified on the Building Regulations tab. Other tabs specify data for heating, cooling, gains and ventilation, are for the purposes of general simulation using ApacheSim or Part L2 (2006).

 

Building regulations data relating to constructions (for instance, whether a window is classified as display glazing) is entered via fields labelled ‘Building Regulations’ within the construction data dialogues in APcdb.

 

The Part L analysis and results dialogue on the lower edge of the <VE> Compliance view is divided into two parts:

Part L1 (2006) – England/Wales/NI - Analysis: facilities for specifying the Part L1 analysis to be performed

Results: facilities for viewing the results of the analysis

This dialogue also provides a route to the Part L1 (2006) ApacheSim building and system data.