EPBD-NCM

General Questions

What is NCM?

NCM is the National Calculation Method developed for DCLGto implement the EPBD. It was defined in DCLG's consultation document on the energy-related parts of the Building Regulations and the Energy Performance of Buildings Directive, issued in July 2004 click here for further details

What is EPBD?

EPBD is the (EU) European Energy Performance of Buildings Directive. Directive Implementation Advisory Group (DIAG) has been established to advise the UK Government on the energy performance of buildings and the implementation of the European Energy Building Performance Directive in a timely manner. For further information click here Part L

Can iSBEM be used in Scotland and Northern Ireland?

iSBEM can now be used for compliance with Building Regulations Part F in Northern Ireland.

The iSBEM_v3.0.b is now suitable to use with the Scottish Building Regulations Section 6.

Is there any training available for the iSBEM?

For further details on iSBEM training, please visit the Training page on the website.

Who do I contact to report a bug?

If you're experiencing problems using the iSBEM software or you have feedback to send to the team, please contact us via the feedback page We aim to respond to your query within five working days.

Building Regulations

How do I find someone certified in the use of SBEM for Part L2A compliance calculations?

The first individuals approved through the BRE Certification Competent Persons Scheme are now listed on their Red Book website. This list will grow as more people go through the scheme successfully. To download the Red Book Live click here the list can be found on page 58. You can now view the list on the website click here choose the option Browse the Red Books then select the Environmental Schemes.

Where can I find the latest Building Regs Part L2a and HVAC guide?

Non-Domestic Heating Cooling and ventilation Compliance Guide

 

 

Building Regulations Part L2a

I have a query on the Building Regulations and Energy Performance Certificates?

If you have specific queries on Part L or Energy Performance Certificate issues, please contact the CLG Part L helpline at:  CLGtechelplinepartflp@fabermaunsell.com

SBEM / iSBEM

What is SBEM and iSBEM?

SBEM stands for Simplified Building Energy Model. SBEM is a computer program that provides an analysis of a building's energy consumption. SBEM estimates the monthly energy use and carbon emissions of a building.

iSBEM is the Interface tool for the Simplified Building Energy Model developed for CLG in compliance to the EPBD.

How often is iSBEM updated?

The current version of iSBEM_v3.0.b is the latest approved version and future changes should be less frequent. Please visit the Latest News page in which we will announce newer versions of the application and manual as and when they are made available.   

What are the requirements to run iSBEM?

Current version of iSBEM (iSBEM_v3.0.b.mdb) runs on Microsoft Access 2002 onwards. We recommend at least 512MB RAM to run the application.

What do the SBEM/iSBEM version numbers mean?

Each release of iSBEM and SBEM will have a version number of the form X.Y.a

'X' will represent the Major Release Number, and will only change when there is a significant enhancement to the functionality or scope of the calculations or the data behind them. This should only change very occasionally - a few times only during the currency of a particular version of Part L.

'Y' is the Minor Release Number, starting at zero, which will change when we make minor improvements, or correct bugs, which have an effect on the numeric result of the calculation

'a'  is a letter representing the version number. This will change when we have to correct bugs which affect the ease of use of the tool, or the presentation of the output, for example, but have no effect on the calculated results.

So the first release should strictly have been v1.0.a. The second is v1.0.b

Where can I get iSBEM?

iSBEM is freely available to download from the Download Page. Please note you will need to fill out your details before downloading

How do I install iSBEM?

Details to install iSBEM are contained in the user manual which can be also downloaded from the Download Page

Will iSBEM run on Vista?

Yes. iSBEM will run on Vista though you will need Microsoft Access installed for it to work. If you don't have Microsoft Access you can order a free copy of the Runtime Access for Vista via the feedback page.

Before you install iSBEM you will need to be logged in as an Administrator. There will be a number of secuirty warnings you need to accept before you proceed with the installation and when you run the iSBEM. These are standard security warnings in built with Vista.

I can't access the F1 help in Vista?

Vista no longer supports the Help files from previous version of Windows. To over come this you will need to download and install the Windows Help program (WinHlp32.exe) for Windows Vista via the link below.

http://www.microsoft.com/downloads/details.aspx?FamilyId=6EBCFAD9-D3F5-4365-8070-334CD175D4BB&displaylang=en

iSBEM freeze's in Office 2007?

When you first run the application in Office 2007 it may not respond when you try to accept the licensing terms and conditions for the SBEM software. You will need to close the licensing box from the X in the top right corner. You will notice a bar across the top of the page with the following text "Security warning - certain content in the database has been disabled". Click the "Options" button, select "Enable this content" then click "OK". The iSBEM is then enabled to run normally on your PC.

I'd like to know more about how SBEM works

We will be producing, for CLG, a Guide to the National Calculation Methodology. It will describe the operation of SBEM, but will have a wider scope than this. Where detailed methods are already described elsewhere - for example in standards - we will refer to them

What is the notional building?

This is defined in the Advisory Documents. In essence, it is a building of the same size, shape and use as the actual building, but with U-values etc that are just compliant with the 2002 regulations.

Does the iSBEM work on other operating systems?

The first approved version of iSBEM has been developed to work on a Windows platform only (Windows 2000, Windows XP and Vista).

Unfortunately iSBEM will not be compatible with Mac or Linux. The SBEM will run on most platforms as it is standard c++ and can be compiled in Mac or Linux, but the iSBEM tool itself will be a Microsoft Access application which will not run on Linux or Macs.

 

How can I access the Help feature in iSBEM?

The "Help" button (labelled with a "?" mark) can be found in the top right hand corner of almost every sub-tab in iSBEM. Clicking on this button opens the Help menu. For the definition of a particular parameter, place the curser within that field and press F1 on your keyboard. This will open a window containing the Help item for that parameter. Alternatively, you can access the information in the iSBEM User Guide.

For a block of flats should SBEM be used for the common areas (corridors and reception)?

Each flat is a separate dwelling and must be assessed using SAP (the relevant guidance is in ADL1A). However, the common areas in the flats are not classified as dwellings. As stated in ADL1A paragraph 14, the appropriate approach to compliance depends on whether the common areas are heated or unheated. If the common areas are heated, the guidance in ADL2 should be applied using SBEM. When defining an envelope element between the common area and a flat, the flat should be classed as a "conditioned adjoining space". If the common areas are unheated, reasonable provision would be to provide fabric elements that meet the fabric standards set out in paragraphs 33 to 36 of ADL1A. 

A new activity will be added to the activity database in a future version of iSBEM for these areas. For now, please select Building type 'Hotel' and activity 'Circulation area (corridors and stairways)'. This activity has no DHW demand associated with it. It is still necessary to assign a DHW generator to these areas, this will not cause any problems in the project because the generator will not be used where there is no DHW demand. The default DHW generator should be used in this case, if gas is not available in the building, the DHW fuel should be changed to any fuel other than natural gas.

If you have queries regarding SAP, please go to the website www.bre.co.uk/sap2005  

On closing SBEM I get error message- Table tempMsysaccessobjects already exists

The quickest way to solve this is to reinstall iSBEM by clicking again on the downloaded .exe file (if you have deleted this you will need to download it again from the website). Before you do this, if you have any projects saved in the iSBEM "Projects" folder, copy this folder to another location on your computer so that your projects do not get overwritten. Once you have reinstalled iSBEM, you can copy the projects folder back into the new iSBEM folder.

Technical Questions

How do I treat communal areas that accompany units with independent heating systems when using iSBEM to produce an EPC?

Please refer to CLG's website at: http://www.communities.gov.uk/planningandbuilding/theenvironment/energyperformance/epbdfaqs/energperformancebuildings/epccommercial/?id=787704#question, which advises the following:

In the guidance (Improving the Energy Efficiency of our Buildings - A Guide to Energy Performance Certificates for the Construction, Sale and Let of Non-Dwellings - section 4.2.2 scenario B1 - a centre with conditioned central space and independent heating systems) - note was made of including a proportion of the energy consumption of the conditioned central space in the EPC for a unit. The following advice should replace 4.2.2 scenario B1 in the guidance:

In practice, where a centre has units and a common space all with independent heating systems, 1 EPC can be provided by a seller or landlord for the whole building only if it is being sold or let as a whole. Otherwise a seller or landlord should provide an EPC for the part (or unit) being sold or let plus an EPC for the common space. The prospective buyer or tenant can then make their decision on the basis of the energy rating for the unit and the energy rating for the common space that serves the unit.

Conversions and Files

I've used the conversion tool to convert my project to the current version, is there anything else I need to do?

Yes:

After converting a project, it is necessary to click through all the forms and tabs to to check all the information is correct. You should also double check and note the parameters listed on the updates page.

Which file do I need to give to my colleague so that he/she can look at my iSBEM project?

In order for someone else to look at your iSBEM project, they will need the nct file for the project. This has the name with the .nct extension which by default is found in the Project folder ( C:\NCM\iSBEM_v3.0.b\Projects).

NCM Databases

Which activity should I choose?

The activity chosen may not exactly match the occupancy, loads etc in the real building, but should be reasonable for a space of that usage type. An important thing to note is that both the notional and the actual building use the same activity parameters (occupancy times and density DHW loads etc), so both the TER (Target Energy Rating) and the BER (actual Building Energy Rating) are determined on the basis of these figures. This makes small differences in parameters from the real building unimportant.

Can I have more than one building type in my project?

It is acceptable in iSBEM to choose more than one building type in a project. For example if you have an office building which contains a small shop, you will notice that there are no suitable 'retail' activities for the building type 'Office'. However, you could change the building type to 'Retail' for this area and choose one of the activities included for the retail building type. Generally though, if there is a suitable activity under the default building type, you should use this.

Some of the information in the databases is incorrect

We have tried to use information from established sources, but this has not always been possible. Please tell us which information you doubt, so that we check and, if necessary, correct it.

How can I modify the parameters in the activity database?

You can't. The parameters associated with each activity are standardised to allow consistent comparisons between buildings and can not be modified by the user.

What do I do if I'm using materials with different properties from those in the construction database?

You can enter your own constructions into iSBEM. You will need to calculate the U-value and effective thermal capacity - and to have evidence that these figures have been properly calculated.

Zoning

What is an indirectly conditioned space?

An indirectly conditioned space is one in which it is intended that the heating, cooling or ventilation is be provided indirectly from an adjoining space. An example of this would be a corridor next to offices which is not directly heated but is conditioned through the movement of heat and air from the adjacent offices. An indirectly conditioned space should be considered to be conditioned by the HVAC system that supplies the most important surrounding area. Elements between a (directly)  conditioned space and an indirectly conditioned space should be labelled as adjacent to a "conditioned adjoining space" and NOT to an "unheated adjoining space"

I have heard that daylight zoning is no longer required. Is this true?

Sub-dividing zones according to daylight is part of the NCM zoning rules and is still applicable. However, a new feature in version 3.0.b of iSBEM gives the user the option to either do the subdivision themself, as with previous iSBEM versions, or let the tool do it instead, i.e., the user would enter the zones as per the other zoning rules but without applying the daylight sub-division and select to let SBEM automatically sub-divide the zones into daylighting sub-zones, if needed, following the zoning rules for zones with access to daylight from windows and rooflights. If you select not to let SBEM do the sub-division automatically, then you need to specify the percentage area of each zone where the lighting is controlled so as to respond to daylight. If that percentage is entered as 100%, this means that the whole area of the zone has lighting controls that respond to daylight, and SBEM will perform no further sub-divisions for this zone (this is the case if you have already done the daylighting sub-division yourself). If the percentage value that you enter is less than 100%, for e.g., 70%, then SBEM will sub-divide the zone into two daylight zones whose areas are 70% and 30% of the total area of the zone, respectively. SBEM will then consider that the 70% daylight area will have lighting controls responding to daylight while the lighting in the 30% daylight area will not be affected by daylight. NB: If your zone has a non-typical layout of windows and/or rooflights, and you are worried that SBEM's automatic sub-division might not correctly reflect the access to daylight in the zone, it is recommended that you carry out the daylighting sub-division yourself, as with previous iSBEM versions.

In iSBEM version 3.0.b, where can I enter the number of corners for each zone?

Version 3.0.b of iSBEM is able to calculate the number of corners for you so you no longer need to calculate and input the values yourself.

How do I decide whether a space is unconditioned or indirectly conditioned?

It depends on whether it is easier for heat to flow between the space and outside or between the space and adjacent conditioned spaces.  A few guidelines are:

(a) if a space has no elements that are adjacent to outside (but does have elements adjacent to conditioned spaces) it is indirectly conditioned.

(b) if the elements between the space and the outside are insulated, but those between it and adjacent conditioned spaces are not, it is also an indirectly conditioned space.

(c) if the elements between the space and adjacent conditioned spaces are insulated (for example in an atrium), it is an unconditioned space.

How should risers and other small unconditioned spaces be treated in SBEM?

Small unconditioned areas such as small risers and store cupboards can be absorbed into adjacent conditioned spaces. In iSBEM this would involve adding their floor area to the adjacent conditioned space. For larger areas, these areas should be treated as indirectly conditioned spaces (see FAQ on this subject above).

Errors

When using the tool I receive an error 'Cannot open any more Databases'

This sometimes occurs with MS Access. If you see this error, click on 'OK' and move to another top level form (e.g. move from 'Building Services' to 'General').

The program crashes or produces an error

There is an error file (text file) produced by the tool named .err which may give you more information about the error. This will not report all errors depending where in the calculation they occur. There is also an error file for the notional building _not.err. If the program crashes or produces an error and looking at these files does not help, send the nct file for the project to sbem@bre.co.uk so that we can investigate further.

Notional Building

In a hospital, I have a space that contains activities that require high ventilation rates and high pressure drop filtration. This inevitably generates auxiliary energy demands well in excess of those of the notional building

It is proposed to revise the activity database and the definition of the notional building to cover this situation. In principle, reasonable provision would be to apply an SFP of 2.0 to the minimum necessary fresh air flow rate if HEPA filters are not necessary, or a value of 3.0 if they are. 

Default values

Some of the default values do not comply with Building Regulations

That's right - they are intended to apply mainly to existing buildings. The user needs to positively attest compliance - for example, by inserting the values that apply to the particular building. We could make the defaults automatically compliant, but that would still leave the user to ensure that the building complies when built.

Overheating

I notice that iSBEM version 3.0.b lists results of an overheating calculation in the compliance document. Do I still need to do the overheating calculation separately?

The overheating calculation implemented in SBEM version 3.0.b was originally developed to provide guidance for recommendations accompanying EPCs, and discussions are currently taking place regarding possible refinements of the calculation for building regulations compliance checking purposes. Hence, a modified version of this calculation might be available in the future. In the meantime, you will need to continue carrying out the overheating compliance check separately outside SBEM as you have been doing with versions prior to 3.0.b.

Project Database Tab

U-values and CM values

Why are the construction thermal mass (CM) values different in Northern Ireland from those for the rest of the UK?

In Northern Ireland builders tend to use wet plaster rather than plasterboard, and this leads to higher thermal mass (CM) values. 

Changing the U-values doesn't have much effect on the results.

In some non-domestic buildings, heating is responsible for only a small part of the carbon dioxide emissions. Further insulation then has a limited effect and may increase the cooling needs.

How is the CM value (effective thermal capacity) calculated for a construction?

The CM values are calculated by:

For each construction element:

Calculate the contribution of each layer of construction as density (kg/m3) x thickness (m) x specific heat capacity (kJ/(kgK))

Starting from the layer of the construction closest to the space add these values together until any one of the following conditions is satisfied:

the total thickness of layers exceeds 0.1 m

you have reached the mid-point of the construction

you have reached an insulating layer

Metal Cladding

What is the definition of metal cladding?

Constructions involving metal cladding are roof or wall systems where metal forms an integral part of the construction, such as metal twin skin systems where the insulation is located between the metal skins and where the metal skins are typically in the range 0.4 mm to 1.2 mm.  Cladding with z-spacers would come into this category as would composite metal panel systems.

If the metal is simply used as an external shield against weather, such as a rainscreen, this is not classed, for the purposes of SBEM calculations as "metal cladding". 

Metal cladding systems are divided into two broad categories, these being:

(a) built up metal cladding systems involving rail and bracket or z-spacer systems with insulation within the panels

(b) composite panel metal cladding systems with insulation inside the panels

Why do I need to specify whether my construction involves metal cladding?

This information will be used for the building default thermal bridges calculations. In the geometry tab, thermal bridge psi values can be entered, or the user can choose to use the default values. There are different psi values for junctions involving metal cladding and those junctions not involving metal cladding. If either of the constructions involved in a particular junction is a metal cladding construction, the psi value for metal cladding will be used when calculating the heat loss or gain associated with that junction.

Geometry Tab

Areas

When entering the area of a wall with glazing, do I deduct the area of the glazing from the total area of the wall?

No, the area of any envelope element is inclusive of any windows, rooflights, and doors.

What is the Surface Area Ratio for a window?

The surface area ratio specifies the developed to projected ratio for the window. The developed area is the area of the window (glass plus frame) and the projected area is the area of the opening in the wall. So for domed or conical rooflights, for example, this would be bigger than 1. It cannot have a value less than 1.

Psi values

What are psi values and why are they needed?

There are two types of thermal bridges which occur within buildings; repeating thermal bridges and non-repeating.  Repeating thermal bridges should be taken into account when calculating the U-value of a construction.  Non-repeating thermal bridges are dealt with differently and these occur at junctions between building elements and around windows and doors.

iSBEM allows you to define psi values for such thermal bridges. The psi values is the linear thermal transmittance of a thermal bridge, in W/(mK).

For each type of junction, you can enter a Psi value (W/mK) or tick the box indicating whether or not that type of junction complies with the relevant standard. The standard for junctions involving metal cladding are set by the Metal Cladding and Roofing Manufacturers Association (MCRMA) and the standards for junctions not involving metal cladding are Accredited Robust Details.

The defaults for all the junctions in the building have been set to comply with the relevant MCRMA and Robust Details standards, except for the roof to wall junctions involving metal cladding, where a Psi value has been added.

Building Service Tab

General

Why is the VRF option no longer available?

From version v2.0.a onwards, these two system types were removed from the HVAC system type options and replaced by the system type "Split or multi-split system". This change was made in order to simplify the HVAC system options (multisplit can be used for VRF as VRF is a type of split/multisplit system) and in order to remove ventilation from HVAC systems where the ventilation is not an integral part of the system heating/cooling strategy. If these systems are accompanied by mechanical ventilation, mechanical ventilation should now be defined at zone level, with a suitable ventilation SFP.

I have an activity that requires tight humidity control, how can this be entered in iSBEM?

SBEM does not consider energy for humidification and dehumidification in the energy calculations. This may be included in future versions of iSBEM.

I'm using a heat recovery dehumidifier in a swimming pool, how do I take that into account?

SBEM does not consider energy for humidification and dehumidification in the energy calculations. This may be included in future versions of iSBEM. 

You can't specify the boiler size?

For further information you will need to refer to the "Non Domestic Heating, Cooling and Ventilation Compliance Guide" which is available from:

Non-Domestic Heating Cooling and ventilation Compliance Guide

My HVAC system is not included within SBEM, what can I do?

If your system is not included within SBEM it would be acceptable to use a 'workaround' in order to produce results using the existing systems in SBEM. However, decisions made in this process must be justified to building control.

When using a workaround in SBEM, the aim is to calculate the CO2 output of this system in your building. To do this, it is acceptable, where a system is not included in SBEM, to substitute it with another system. If a heating and cooling system exists in the  building, a heating and cooling system must be chosen in order to include cooling in the calculations.

Generally a system with the same fuel type should be chosen, if this is not possible, it may be acceptable to adjust the system seasonal efficiency in order to achieve the same carbon intensity as in the actual system. For example, where a system uses gas for FCU heating coils and an electric heat pump for an associated warm air ventilation system, it could be acceptable to select a FCU system with an electric heat pump and then increase the system COP in order to reduce the carbon intensity of the system to account for some of the heating being provided by gas.

Defining a bivalent system in iSBEM

A bivalent heating system is one in which the heating is supplied by two different types of heat sources. An example could be a heat pump with a gas boiler for backup. Within iSBEM, a fuel type and a seasonal efficiency have to be input in order for the SBEM calculation to produce the overall CO₂ emissions per kWh of the total heating provided by the two heat sources. First, the proportion of the heating demand met by each heat generator needs to be estimated, in a manner that can be justified to Building Control. Then, an efficiency equivalent to the 2 systems based on their respective loads, efficiencies, and emission factors (obtained from ADL2A) needs to be calculated. Also, in order to ensure that the notional building is correctly defined (according to definition in ADL2A), if the fuel of one of the 2 generators is gas, it is necessary to define the fuel type for the equivalent heating system, which is entered into SBEM, as gas. Even if the calculated equivalent efficiency figure in this case is over 100%, this is just an artificial value for a "virtual" boiler needed to produce the correct carbon emissions in the SBEM calculation. If gas is not used in the building, the heating fuel should be defined as oil and the corresponding emission factor for oil is to be used in calculating the equivalent efficiency. Therefore, for example, if a heating system uses a heat pump of COP 3 providing 75% of the annual heating demand, and the remaining 25% of demand is met by a natural gas boiler of 85% efficiency (the CO2 emission factor for grid-supplied electricity is 0.422 kgCO2/kWh and for natural gas is 0.192 kgCO2/kWh), the heating fuel type is entered as natural gas into iSBEM, and the equivalent efficiency can be calculated as follows:

I created a project using an iSBEM version prior to v2.0.a, and it contained a Variable refrigerant flow system or Split or multi-split system, But after converting the file to iSBEM v2.0.a, v2.0.b, or v2.0.c, the system type has become Central heating using water: floor heating. What can I do?

For the answer, please click here.

What is 'AUXILLARY' energy used for?

This is energy used by the HVAC system pumps, fans and controls.

Fan coil units are defined as including central ventilation to the space, which Specific Fan Power (SFP) and flow rate should I enter for this system?

The auxiliary energy figures for this system include an allowance for the fans in the fan coil units, (and there is a minimum acceptable performance figure in the HVAC guide - 0.8 based on the average of all fan coils). The SFP that users input should be just for the central plant - the fan coil allowance will be included automatically. Similarly, the flow rate should be for the central plant.

What enhanced management features are needed in order to claim the adjustment factor offered in Table 3 of ADL2A?

The adjustment factor is available for "automatic monitoring and targeting with alarms for out of range values". This means:

a complete installation that measures, records, transmits, analyses, reports and communicates meaningful energy management information.

It would normally include primary and secondary metering to the standard set out in TM39, with automatic meter reading, transmission and storage of the consumption data to a central point and software that analyses the consumption data, produces reports to predetermined criteria and communicates the resulting information to the energy manager.

The key element over and above the provisions set out in paragraph 43 of ADL2A is the analysis and reporting software. The checks the software carries out and the alarms it raises will be a function of the particular installation, but its purpose should be to immediately highlight any unexpected change in energy demand that might indicate energy wastage. The software should also facilitate benchmarking of measured energy performance.

Does the HVAC system Variable Refrigerant Flow include ventilation to the space at HVAC level?

Yes it does. If your building has a VRF system for heating and cooling only and a separate zone level ventilation system in order to provide the fresh air, you should select the system "split or multisplit system" instead, specifying a generator seasonal efficiency appropriate to your VRF system, and then separately specify mechanical ventilation at zone level

DHW

Why does the DHW energy increase so much when I define the system as a storage system?

In iSBEM the user can either enter the storage volume or losses for the system or can leave the boxes blank so that default values are used. The default values are fairly conservative and assume, for example, that the storage tank is poorly insulated. We recommend that users enter the actual storage losses for the building.

Why does a DHW generator need to be assigned to all zones?

A DHW generator should be assigned to ALL zones where DHW demand is generated. For example, the DHW demand in an office building tea making area is generated by the occupants in the nearby occupied areas in the building, not in the tea making area itself. Therefore the DHW generator in the tea making area should also be assigned to the adjacent office zone.

Lighting

The lighting option of "Lighting chosen but calculation not carried out" is not available. Why?

The lighting option of "Lighting chosen but calculation not carried out" is not available for zones which have been assigned certain activities classed as office, industrial and storage areas. For these areas, Approved Document L2a states that an average luminaire lumens per circuit watt calculation must be carried out. In this case the user can specify the "Full lighting design carried out" option.

In the case where a full design has not been carried out, the option "Lighting Parameters not available" can be used for these areas.

In the lighting controls, how are Hours Off and Fraction Off defined?

These are for display lighting and must be specified if the zone has time switching or dimming for this lighting. If time switching is selected, the hours off specifies the number of hours per average day the lighting is switched off. The fraction off specifies the fraction of display lighting which is turned off by the time switch. If this is 1, all the display lighting is switched off by the time switch.

If dimming is selected, the hours off specifies the number of hours per average day the lighting is dimmed. The fraction off specifies the fraction of display lighting which is dimmed by the time switch.

Ratings Tab

Output Document

Are there more detailed output reports available?

There are various output reports from SBEM which you may find useful when analysing where the energy use occurs. One of these is called "<project name>.sim". If you add .csv to the end of this file name so it is now called  "<project name>.sim.csv", you can open this file in MS Excel. This report gives various information including details of U-values and some other data. Towards the end of the file there is a breakdown of energy use both by fuel type and end use for both the whole project and for each HVAC system.

SBEM results are different to TAS/ IES results for the same building. Why?

All interfaces which uses SBEM as the calculation engine (such as iSBEM and Hevacomp) will show the same results if the same building with all the same details are entered.

Other accredited simulation software such as TAS do not use SBEM as the calculation engine. They may give slightly different results but it is not possible to say if the emissions will be higher or lower as this will depend on the building. It is important to remember that for Part L, you are comparing the emissions from the building you enter to a "notional" building. Therefore if the assumptions/methodologies are slightly different, this will be applied to both the actual and notional building and therefore and differences should be limited