Guidance on performing Part L2 (2013-2014) assessments

The <VE Compliance> View provides the means to test compliance with the conservation of fuel and power requirements of the UK Building Regulations, including (but not limited to) the Part L2 2013 regulations applying in England and L2 2014 regulations applying in Wales.

The following guidance is aimed at providing an overview of the implementation of the Part L2 2013-2014 Building Regulations in the VE software. Much of this guidance can also be applied to the improvement of EPC ratings.

 

New Part L2 regulations came into force in England on April 6^th 2014 (31^st July 2014 for Wales), and apply to non-domestic buildings beginning construction after this date. The regulations require designers to demonstrate further reductions in carbon emissions from building energy use relative to the standards set by the previous editions of the regulations. This is achieved by performing a detailed analysis of the carbon emissions of two buildings:

·       The actual building – the building as designed, but subject to standard patterns of occupancy and plant operation, and

·       The notional building – a version of the building that conforms to the standards defined in the National Calculation Methodology (NCM) Modelling Guide (for buildings other than dwellings in England/Wales) 2013/2-14 Edition ^[3] respectively.   The notional building is subject to the same occupancy and plant operation patterns as the actual building.

The analysis must demonstrate that the actual building’s carbon emissions improve on those of the notional building. It is this improvement that constitutes the tightening of the regulations in the 2013-2014 editions.

 

The analysis of carbon emissions must be performed with accredited software applying the National Calculation Methodology (NCM), implemented in a DSM method such as ApacheSim or BRE’s SBEM program (driven by either the native iSBEM interface or a proprietary interface such as VE-SBEM).

The actual building’s performance must improve on that of the notional building.

Assessments must be performed under standard occupancy and plant operating conditions. This means that under the new regulations, some of the data entered by the user to model the building for design work has to be replaced by different data for the purpose of compliance analysis.

It should be remembered that Part L2 places the requirement for standard occupancy and plant operating conditions on a model. The consequence of this is that, in addition to the actual and notional buildings, the designer will usually need to model and analyse (for design and other non-regulations purposes) a third building:

·       The real building – this is the building as designed, and with the occupancy and plant operation conditions expected to apply in reality, rather than the standard conditions stipulated for Part L2 compliance.

The real building is the building presented in the Apache View, where the special conditions required for NCM analyses are not applied.

 

The testing of carbon emissions constitutes Criterion 1 of Part L2. The full set of criteria is as follows:

·       Criterion 1 – Achieving the Target Emission Rate (TER).

·       Criterion 2 – Limits on design flexibility: this sets minimum standards for building fabric and system performance.

·       Criterion 3 – Limiting the effects of heat gains in summer: this imposes limitations on solar gains but is not in itself evidence that the internal environment of the building will be satisfactory.

·       Criterion 4 – Building Performance consistent with the BER: Quality of construction and commissioning: this lays down requirements that the building must meet after construction. (Not covered by VE Compliance.).

·       Criterion 5 – Providing for energy efficient operation of the building: certain information must be provided to the owners of the building. (Not covered by VE Compliance.).

Users of the VE Compliance software are strongly advised to study the official documents defining the regulations.

In the IES Virtual Environment all building regulations compliance testing is performed in the VE Compliance View. This covers range of regulations for England, Wales and Northern Ireland as applied to both dwellings and non-dwellings, together with their counterparts in Scotland.

The starting point for a compliance analysis is the input of geometrical data in ModelIT. The Template Manager, a central resource available from all Views, is typically used next to set up room system and ventilation parameters. Apache View, while not essential for compliance testing, commonly plays a part in the input of data for ratings (compliance and EPC) analyses that is shared by other Apache View applications, and Views such as SunCast and MacroFlo may also be invoked. The purpose of this section is to provide an overview of the roles played by the different parts of the VE in the compliance testing process.

 

ModelIT handles the input of the building geometry.

The Template Manager provides facilities for setting room conditions for a range of thermal applications. In the context of ratings, it also allows the specification of room activities that define the standard occupancy and plant operation conditions that apply in NCM procedures. In compliance tests these standard conditions automatically override certain of the Space Data settings that would otherwise be taken from the Room Template.

Apache View covers thermal applications such as heating and cooling load calculations, and simulation outside the context of ratings. The analysis in this View applies to the real building, for which all the input data is under your control. Where data is shared between the real building and the actual building, this data may be entered in either Apache View or VE Compliance. Examples of such shared data include:

·       Location

·       Constructions

·       HVAC systems

·       Renewables

VE Compliance covers thermal analysis specific to UK ratings analysis (Building Regulations compliance and EPCs. Some of the data required by ratings is shared with Apache View, as indicated above, and may be entered or edited in either View. Other ratings-specific data must be entered in the VE Compliance View. This includes:

·       Regulatory framework – e.g. Part L2 (2013) (assumed in the list that follows)

·       Building type

·       Room activities (may be specified by means of templates)

·       Data relating to lighting and lighting control

·       Heat bridging data

·       Stage of analysis (Design or As Built)

·       Data required by the BRUKL compliance calculator, including addresses, system characteristics and air-tightness properties

By default, VE Compliance displays data for the actual building. The notional building may also be inspected in this application. Facilities are provided for performing compliance simulations, test compliance simulations (on both the actual and notional buildings) and summertime temperature analyses for Criterion 3.

SunCast analyses shading and internal solar penetration, factors which may optionally be taken into account in compliance simulations.

ApacheHVAC and Radiance are other Views covering component-based HVAC system simulation and lighting simulation, respectively, that are also available as adjuncts to compliance simulations.

Vista provides facilities for viewing the results of VE Compliance and other simulations.

The definition, creation and purpose of these three buildings can be summarized as follows.

The real building is the building that you see in the Apache application. It is the building as designed, and with the occupancy and plant operation conditions expected to apply in reality, rather than the standard conditions stipulated for UK ratings analysis. In the Apache module it forms the basis for the analysis of heating and cooling loads and simulations.

The actual building is the building as designed, but subject to standard patterns of occupancy and plant operation for UK ratings as defined in NCM. The actual building is the building displayed by default in VE Compliance. It has the same geometry and construction as the real building but its activity settings (occupancy, internal gains, heating and cooling set points and minimum ventilation rates) and plant operation conditions are assigned standard settings in VE Compliance as a function of the NCM activities assigned to its rooms. It is also subject to rules governing the calculation of infiltration and auxiliary energy. Aspects of the actual building that are shared with the real building may be edited either Apache View or VE Compliance.

The notional building is a version of the actual building modified to conform to a clearly defined set of standards relating to glazing area, constructions and system characteristics. Its purpose is to provide a benchmark or target against which to measure the performance of the actual building. The notional building is subject to the same occupancy and plant operation patterns as the actual building. It can be viewed in VE Compliance by switching the Current Model from Actual to Notional. It is created automatically from the actual building, and may not be edited. (One exception to this rule is dealt with below.)

Users interested in compliance testing only are not obliged to consider the real building as an entity distinct from the actual building. They can thus bypass Apache View. They should, however, be aware that certain room template attributes are overridden in VE Compliance.

Aside from this point, which is covered in more detail below, the real building does not need to be considered further in the context of VE Compliance.

The actual and notional buildings, however, can usefully be described in more detail.

The actual building allows you control over the following aspects of the design, which it shares with the real building.

Data shared between actual building and real building:

·       Location

·       Geometry (including orientation and glazing)

·       Constructions

·       Most system characteristics including renewables

The actual building differs from the real building in terms of its occupancy and plant operation, which for the purpose of UK ratings analysis are forced to standard patterns linked to the activity associated with each room. The data in this category is

Activity (NCM Template) Space Data:

·       Occupancy

·       Equipment gains

·       Lighting illuminance levels (these, however, are subject to some flexibility, as well as options on control)

·       Room conditioning (heating and cooling set points and operation periods)

·       Minimum ventilation rates

For the purpose of UK ratings analysis, this data is outside your control and cannot be edited. Note that these attributes are present in the Room Template for use in the Apache module analyses, but the settings appearing there are overridden in the ratings analysis.

 

The standard settings for VE Compliance are brought into the room by means of a second template called the NCM Template which is applied in combination with the usual Room Thermal Template. The NCM Template contains the standard operating conditions (as listed above) associated with the room’s NCM activity. For example, a room assigned the activity ‘Open plan office’ in a building of type ‘Office’ has an NCM Template called ‘NCM Office: Office (Office: Open)’. This contains the occupancy and equipment gains, the lighting level and profile, the room conditioning settings and the minimum ventilation regime laid down as standard for NCM assessments of an open plan office. NCM Templates appear in the list of Room Templates in the Template Manager, where they can be examined in detail.

The activity (sometimes called the NCM activity) is assigned to the room on the Space Data Building Regulations tab, and may optionally be specified by means of the corresponding attribute in the Room Template. The activity, which is always associated with a particular building type, exists solely for the purpose of building regulations and is only used by VE Compliance. Setting the room activity automatically assigns the correct NCM Template and all the data associated with it. The name of the NCM template, together with that of the room template, can be seen displayed on the General tab of the Space Data dialog.

Not all the Space Data is set by the NCM Template. Just as in the Apache module, each room in VE Compliance has a Room Template, and this sets the parts of the Space Data that are not covered by the standard activity settings – namely

·       User-supplied Space Data:

·       System characteristics

·       Measures to improve the efficiency of lighting systems

The Space Data displayed and used in VE Compliance is thus drawn partly from the NCM Template and partly from the Room Template, as follows.

The data on the Building Regs tab is entirely supplied by the user, with the exception of the NCM Template specifying the NCM activity (which the user may override).

The data on the Room Conditions tab is drawn entirely from the NCM Template. These parameters, which include set points and operation times for heating and cooling plant and hot water demand, are fixed for ratings analysis by the room activity, and override the corresponding settings in the room template.

The data on the System tab is drawn entirely from the room template. The system parameters are under your control, and may be adjusted as part of the process for achieving compliance.

The data on the Internal Gains tab is, with one permitted exception, drawn from the NCM Template. Occupancy and equipment gains form part of the standard pattern for the activity. Lighting operation must also follow the pattern laid down for the activity, and must deliver a given minimum illuminance, but here it is permitted to adjust the power consumption to reflect the actual lighting design. It is also permitted to implement daylight-linked lighting control by means of an approved simplified analysis (specified via an option on the Building Regs tab) or other means.

The data on the Air Exchange tab is drawn partly from the room template and partly from the NCM template. The NCM template stipulates ventilation rates for the activity, and these appear as Auxiliary Ventilation air exchanges, replacing any air exchanges of this type appearing in the room template. Other types of air exchange – those of type Infiltration and Natural Ventilation – are taken from the room template.

By applying these rules, VE Compliance automatically sets the attributes that are laid down by the room’s NCM Activity, while giving you control over those aspects where good design can produce energy and carbon savings – namely system performance, infiltration (air-tightness) and ventilation strategies involving the use of outside air for cooling. To this list can be added improvements to the building fabric and system characteristics, which of course do not feature in the room template data.

It should be added that wherever the room template is mentioned above, there is (as usual) the option to override the template settings manually in individual rooms or groups of rooms. However, NCM template settings cannot be overridden in this way, except in the special case of lighting gains.

System characteristics for the actual building (which it shares in the main with the real building) are set by means of Apache Systems, or optionally ApacheHVAC systems. A suitable set of systems should be created and assigned to groups of rooms. The ‘UK NCM system data wizard’ facilitates this process and allows the system characteristics to be specified using an iSBEM-like interface.

The notional building is derived automatically from the actual building according to rules laid down in the NCM methodology. These rules are set out in full in the official documents and what follows is a summary.

The location and geometry of the notional building (with the exception of glazing and door area) are copied from those of the actual building:

Glazing in the notional building is modified depending on the activity type, and there are particular rules applying to areas of display glazing and doors.

The notional building is assigned standard constructions for external elements – walls, roofs, floors and glazing. A special rule applies to ground floor constructions. Where the actual building has spaces that are designated ‘Unheated roof’, ‘Unheated buffer space’ or ‘Glazing cavity’ – indicating spaces that form part of the building envelope rather than the occupied areas – these spaces are absorbed into the elements by which they connect to the occupied areas in the notional building, which are assigned the appropriate standard constructions.

Rooms in the notional building are assigned the same NCM templates as their counterparts in the actual building, so that the occupancy, gain and plant operation regime in each room conforms to the appropriate NCM Activity.

In the notional building, Space Data that is not covered by the NCM activity (and which in the actual building is set by means of the Room Template) is also set by the NCM Template, which in respect of these attributes contains the data stipulated in the official notional building definition. There are also rules applying to infiltration rates.

 

Each space in the Notional building will have the same level of servicing as the equivalent space in the Actual building. In this context, “level of servicing” means the broad category of environmental control, summarised as follows:

a.       unheated

b.       heated only with natural ventilation

c.       heated only with mechanical ventilation

d.       air-conditioned

e.       mixed-mode, where cooling only operates in peak season to prevent space temperatures exceeding a threshold temperature higher than that normally provided by a full air-conditioning system.

Rooms which in the actual building are served by an Apache System of a given type are assigned the appropriate NCM notional building system in the notional building.

The reference building which features in the EPC analysis is derived in a broadly similar way to the notional building, following a different set of rules laid down in the NCM methodology.