Steps to Performing Analysis

 

The following workflow is recommended for preparing and performing a <VE> Compliance analysis for Part L2 (2006). The plan need not be followed slavishly. Variations can be made in the ordering of the tasks and experienced users may wish to take alternative approaches to some of the stages. The purpose of the plan is to guide you through the basic process. (Extra data required by the SBEM-EPC method is not described in this section.)

 

The process usually begins with the entry of building geometry in ModelIT.

The building location is specified in the SBEMlocate utility. The L2 regulations currently specify 11 locations in England and Wales, but the use of any of Edinburgh, Glasgow or Belfast is also permitted if local circumstances make this appropriate.

On the other hand, Part F *requires* the weather location to be Belfast.

Unlike the ApacheSim route, it is not necessary for a VE-SBEM user to purchase the TRY and DSY weather files from CIBSE as SBEM holds this data internally.

Constructions for building elements such as walls, roofs and glazing are created in the Constructions Database (CDB) utility accessible via Apache View or <VE> Compliance. They should satisfy the U value requirements of Criterion 2. The construction definition should include allowance for non-repeating thermal bridging, using an area-based thermal bridging coefficient. Constructions may be assigned to building elements in either Apache View or <VE> Compliance.

Note that VE-SBEM assumes the ground floor U values entered in CDB have already been corrected in accordance with EN ISO 13370. This also means the floor area/perimeter method of calculating the ground floor should not be used, because it does not incorporate this correction. (This is different from iSBEM, which does allow uncorrected U values, with SBEM applying the correction internally).

At this stage you may wish to go to <VE> Compliance and set up some of the high-level data required for the compliance analysis.

First check that the Regulatory framework selector is set to ‘Part L2 (2006) – ApacheSim’.

In the ‘Building settings’ box near the bottom of the screen select a building type from the list. This indicates the type of building for Part L2 purposes and determines what room activities can be specified in the building. It also automatically sets the Building Category, which determines glazing areas in the notional building.

For a building with multiple use, the various parts can be analysed by including NCM activities from other NCM building types.

Not all zones may need to be included in a compliance run for example separate buildings may exist within the same model. The part(s) of the building included in a particular analysis is defined by the settings of the check boxes ‘Include room in Building Regs analysis?’ for each room on the Space Data Building Regulations tab.

An efficient way to assign Space Data is by means of Room Templates. A Room Template contains a collection of settings that define the internal conditions applying in a room of a given kind. By defining these conditions centrally you can assign them quickly to large numbers of rooms and transfer them readily to other models via the Import Template mechanism.

Room Templates contain data arranged on tabs under the headings Building Regulations, Room Conditions, Systems, Internal Gains and Air Exchanges. Not all this data is used in <VE> Compliance assessments, some being overridden by standard settings. It is therefore important to understand where and how the various components of Room Template data are used. In particular, if you do not intend to use the analysis options available in Apache View (which analyses the real building) you do not need to set Room Template data on the Room Conditions and Internal Gains tabs, or create air exchanges of the Auxiliary Ventilation type.

One of the attributes that can usefully be set in the Room Template is the NCM Activity, which is always partnered with an NCM Building Type. If these attributes are set in the Room Template, rooms assigned the template will automatically have the NCM Activity (and all the Space Data associated with it) set in <VE> Compliance.

If you adopt a policy of including NCM Activity settings in your Room Templates you will save a lot of time and effort assigning NCM Activities to individual rooms and groups of rooms in <VE> Compliance.

The next section provides guidance on the Room Template settings.

When creating Room Templates it is important to understand which Room Template settings will be used in <VE> Compliance and which are overridden by standard activity-based settings.

This tab contains data used exclusively by <VE> Compliance. Some of the fields can be set in the Room Template. Others appear only in the <VE> Compliance Space Data and must be set on a room-by-room basis.

The check box ‘Include room in Building Regs analysis?’ allows you to restrict the Part L analysis to part of the building only.

The ‘Type of room’ attribute is normally set to ‘Heated room’, but the following alternative settings are provided to cover various types of unheated space:

Unheated roof – use this type for an unheated roof space lying outside the insulated building envelope (ie where the insulation is at ceiling level).

Glazing cavity (required only rarely) – use this type for a glazing cavity that has been modelled as a separate room for calculation purposes.

Unheated buffer space – use this type for other types of unheated space attached to the building but lying outside the insulated building envelope. Examples are car parks and lean-to outbuildings.

Internal void or warm roof – use this type for floor and ceiling voids, and for roof spaces that lie inside the insulated building envelope (ie with insulation at rafter level).

In the case of the first three types listed above – all representing types of unheated buffer space – an external ventilation rate must also be entered for the purpose of calculating U values for Criterion 2. All the above types of room are excluded from the floor area summation upon which the emission ratings are based.

The settings NCM Building type and NCM Activity together specify the activity assigned to the room for the compliance analysis, which in turn (via the NCM Template) sets the standard conditions applied for occupancy and plant operation. While these attributes are optional in the Room Template, it is a good idea to set them there to save effort in <VE> Compliance.

The building regulations tab has specific SBEM information; reference should be made to the BRE iSBEM user manual for description of terms. Within this section the air permeability, zone ventilation (supply & extract), destratification fans and SBEM lighting data can be defined.

The data set on this tab in the Room Template will be ignored in <VE> Compliance (but it will be used for assessments of the real building in Apache View).

In <VE> Compliance, the data on this tab can be viewed but not edited. It is taken from the NCM Template as part of the specification of standard occupancy and plant operation conditions.

The data set on this tab in the Room Template will be used in both <VE> Compliance and Apache View.

In either of these views, data on this tab is initially taken entirely from the Room Template (but as usual you have the option to override this data in individual rooms).

For compliance assessments, the important parameters on the System tab are the following.

In the Systems box:

HVAC system – this indicates the Apache System serving the room’s space conditioning needs

DHW system – this indicates the Apache System serving the room’s hot water needs including any solar energy system

In the System outside air supply box:

Free cooling flow capacity – this indicates the maximum intake of outside air that is available for free cooling. In the case of a naturally ventilated room, a value of 5 ach would be typical to model ventilation by window opening. In the case of an air conditioned room, where the outside air is brought in via the system, it would be usual to express the value in l/(s·m²) and a value of 0.5 in l/(s·m²) would be typical. Note that this figure represents the additional outside air intake over and above the minimum ventilation level. Free cooling is covered further in the User Guide.

Parameters on the System tab that can be ignored are:

Auxiliary ventilation system – this is not applicable because under the NCM conventions there is no conditioning of ventilation air.

Sizeable parameters (shown in blue) – sizing plays no part in <VE> Compliance.

Humidity limits – these are disabled for <VE> Compliance assessments in line with the conventions applying in the NCM systems approach.

Flow rate and profile for System outside air supply – in <VE> Compliance this type of air supply is replaced by standard ventilation patterns handled by Auxiliary Ventilation air exchanges.

The setting of data on the System tab is closely linked with the setting of data in Apache Systems, which is dealt with below.

The lighting data for VE-SBEM is defined via a button on the Building regulations tab.

Air exchanges are covered by the SBEM data on the Building regulations tab.

It is recommended that HVAC and DHW systems characteristics for <VE> Compliance analysis are specified within the framework of Apache Systems. Apache Systems provide a robust and uncomplicated system model that has been harmonised with that provided in iSBEM with the aim of providing a point of reference and common ground between these alternative compliance methods.

Systems are one of the aspects of building design where substantial carbon emissions improvements can be introduced. The system data is therefore under your control, and it is shared between the real building (as displayed in Apache View) and the actual building (as displayed in <VE> Compliance).

The Apache System HVAC model has three key parameters, which can be defined in summary as follows:

SCoP – the efficiency of the heating system

SSEER – the efficiency of the cooling system (if present)

Auxiliary Energy Value – energy required for fans, pumps and controls

These are the most important parameters featuring in the calculation of the energy consumed by the space heating and cooling systems. Taken together with the fuels specified for heating and cooling, they encapsulate most of the important data about system performance in relation to carbon emissions.

On the Apache System dialogue there are other parameters that are linked with the heating and cooling system efficiencies and do not represent independently editable settings. For example, the heating system’s Generator seasonal efficiency and Heating delivery efficiency are linked to the SCoP by the relation

SCoP = (Generator seasonal efficiency) × (Heating delivery efficiency)

so that in terms of carbon emissions they can be viewed as secondary to the SCoP.

On the cooling side an analogous relationship exists between SSEER and the following parameters:

EER – the cooling system generator energy efficiency ratio or COP

CDE – the cooling delivery efficiency, and

HRP – the heat rejection pump and fan power fraction

namely

SSEER = EER * CDE / (1 + (EER + 1)*HRP)

In terms of carbon emissions EER, CDE and HRP can thus be viewed as secondary to the SSEER.

These ‘secondary’ parameters are important for certain design tasks in Apache View – for example the calculation of boiler and chiller loads. But for <VE> Compliance, SCoP and SSEER are the key efficiency measures.

Auxiliary energy value is a concept that has been developed in connection with the NCM methodology. This parameter indicates the power consumption of fans, pumps and controls associated with the space heating and cooling systems. It is expressed in terms of Watts per square metre of floor area served, and is incurred when the heating and cooling systems are running.

Parameter values can be entered directly into the Apache System dialogue. But it will usually be appropriate to make use of the UK NCM System Data Wizard to assist this task.

The UK NCM System Data Wizard has been based on the analogous facility in iSBEM. Its purpose is to guide you through the process of describing the system properties and to generate values for the three key parameters.

In addition to the key parameters mentioned so far, there are other system parameters of importance such as heating and cooling system fuels and ventilation heat recovery effectiveness. These are also generated automatically from data entered in the wizard.

More information on using the wizard is provided in the <VE> Compliance User Guide.

New nomenclature for heating, cooling efficiencies has recently been introduced that aligns <VE Compliance> with the NCM. Definitions of these can be found in the DCLG document ‘Non-Domestic Heating, Cooling and Ventilation Compliance Guide’. This is freely downloadable from the DCLG website:

http://www.odpm.gov.uk/index.asp?id=1130726

SCoP and SEER values for commonly available plant can be found at:

www.eurovent-certification.com

The DHW system wizard enables the definition of the delivery efficiency, storage and the secondary circulation efficiencies and pumping power. The DHW heating demand can be derived from a solar water heating system. This system will use solar power, when available, to pre-heat the water for the DHW system. A storage system can be defined for the solar water heating system.

Note that Apache Systems may be imported from other projects on the back of Room Templates, allowing system data to be transferred between projects.

Four renewable systems are available for use within the actual building; CHP, Wind, PVs and Solar water heating. CHP should be sized to provide the base load of heating for the building and the power generated will be used to offset the electrical energy usage in the building. Wind and PVs will, when the prevailing weather conditions permit, provide electrical energy that will offset electrical energy usage in the building.

The carbon emission factors to be used in L2 (2006) compliance assessments are stipulated in the NCM methodology for a range of fuels. The Fuels Data facility in Apache View and <VE> Compliance allows fuel carbon emission factors to be edited. The default values are those which conform with NCM. For compliance runs, any departure from these values, or use of fuels not on the NCM list, would need to be carefully justified in supporting documentation.

We now return to the Building & System Data dialogue to prepare for the compliance calculations. For VE-SBEM, Building & System Data is distributed over three tabs.

First, on the General tab, fill in the address and contact details.

Then move to the Building & System Performance tab. This contains data required by the BRUKL compliance checker that collates the calculation results and generates the compliance report.

Building air permeability at 50 Pa – this is not yet available in VE-SBEM.

Location Description – optional

Project Complexity – Level 3, 4 or 5

Related party disclosure – optional

Stage of analysis – As built or As designed

The remaining parameters appear in the box labelled ‘Adjustment for management features’. These settings allow credit to be taken in the BER calculation for management features applied to electrical power and lighting:

Electric power factor

Lighting systems have provision for metering?

Lighting systems metering warns of ‘out-of-range’ values?

 

The final tab deals with Thermal Bridging which SBEM applies to all junctions. If nothing is changed on this tab the default psi values shown will be used. To obtain non-accredited defaults for any or all of the non-metal clad junction types, uncheck the box(es) on the right before clicking the “Restore defaults” button.

When you are satisfied that the actual building model is defined as intended, click on the button ‘CO2 Emissions: Part L compliance’.

The progress of the SBEM calculation is indicated on the screen.

Results from both buildings, together with data provided on the Building & System Data dialogue, is then fed into the BRUKL compliance calculator. The calculations performed there to produce the Building CO₂ Emission Rate (BER) and Target CO₂ Emission Rate (TER) are set out in Appendix B

When the process is complete a summary of the result of the Part L2 analysis will be displayed on the Results tab, and you can click on a button to display the compliance document generated by BRUKL. Any failures are shown in red text in the document.

If the result is a pass for all of Criterions 1 – 3 you may move on to the next stage.

Otherwise you will need to improve the design and try again.

Assuming a successful outcome, the Part L2 (2006) compliance process is now complete in relation to those aspects that can be tested before construction. The reports generated, together with appropriate supporting evidence, can now be submitted to Building Control.

The content of Part L submissions should be agreed in advance with the local Building Control officer as there may be differing interpretations during the early stages of implementation of the new regulations. These are likely to be resolved over time as a sufficient number of Competent Persons are trained and accredited. It may be necessary, for instance, to agree how compliance with Criterion 4 will be met post construction as part of the pre-Construction report.