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If you want a school, hospital or retail scheme to achieve Part L, design time may be most usefully spent on certain services. Andy Pearson reveals how

Are some types of schemes easier to make compliant with Building Regulations? How does the design of a building’s services impact on its ability to comply with Part L? How important is the efficiency of a heating scheme for a hospital? And is it more important to focus design time on this rather than on the lighting?

These are just some of the questions IES Consulting set out to answer by analysing its database of 150 non-domestic buildings that have achieved compliance since the Part L revisions came into effect in April 2006. “We had noticed trends in the ability of different building types to comply with the Building Regulations,” David McEwan, director of IES explains.

IES Consulting is a division of Integrated Environmental Solutions, the building performance analysis software developer. The consultancy uses the firm’s government-approved dynamic simulation modelling software, VE Compliance (part of the Virtual Environment suite of software), to model schemes for a variety of clients.

The consultancy analysed four types of building: schools, offices, hospitals and retail. For each of them, researchers looked at the key building services elements that make up the CO2 emissions as defined by the National Calculation Method (NCM), the government-approved procedure for demonstrating compliance with the Building Regulations for properties other than dwellings. These elements are heating, cooling, lighting, domestic hot water and auxiliary energy, such as the power consumption of fans, pumps and controls.

Using its database, IES Consulting set out to discover the critical services elements on which a designer should focus for each building type, in order to achieve sufficient CO2 reductions to pass the Building Regulations.

Although the research was based on Part L 2006, the similarities between the regulations for England and Wales, Northern Ireland’s Part F (November 2006) and Scotland’s Section 6 (May 2007) mean the results will be broadly applicable for buildings across Britain.

According to McEwan, hospitals are one of the easiest building types to pass Part L 2006, while retail units can be more difficult because the NCM database focuses on electricity, which shops use in abundance for lighting.

The findings for each building type are given overleaf. IES looked at a number of buildings for each type and then used a representative example. However, the decision on which energy-saving measures should be incorporated to ensure compliance is dependent on a variety of factors that need to be considered in the context of the building. “Schools, for example, must comply with Building Bulletin 101 for environmental design and certain comfort parameters must be met,” explains McEwan.

Offices

Key issues:

Lighting, auxiliary energy and cooling make up the most significant proportion of CO2 emissions in the notional office building.
Heating is also significant.
Air-conditioned offices offer more scope to achieve reductions in CO2 emissions, which is why they are perceived as being easier to make compliant with Part L.

Typical solutions:

Getting the lighting design right is important and usually offers an easy route to achieving significant CO2 reductions.
Maximise the use of daylight to reduce lighting gains.
Use more efficient cooling systems (whether based on mechanical air-conditioning or mixed-mode ventilation), thermal mass, shading or heat recovery.

Hospitals

Key issues:

Hospitals tend to be one of the easiest types of buildings to pass Part L.
Domestic hot water and heating are more significant in this type of building than others.
The detailed, complex geometry of these large schemes generally means it is essential to use accredited dynamic simulation modelling software.

Typical solutions:

Efficient heating and cooling systems are necessary because of the continuous occupancy. A combined heat and power solution is ideally suited to hospitals as there is always demand for heat, even in summer. Other options include local hot water generation and absorption cooling.
The lighting needs to be efficient, but this is generally not an area where significant Co2 savings can be made easily.

Schools

Key issues:

Lighting and heating are the most significant contributors to the target CO2 emissions rate.
Lighting offers the easiest and greatest reductions in CO2 emissions because it is powered by electricity, a high emitter.
Heating usually provides the second most easily achievable reduction in the emission of CO2.

Typical solutions:

Shading to classrooms to avoid overheating and glare.
Energy efficient lighting design to reduce energy usage.
Rooflights to maximise daylight in internal areas.
Natural ventilation to classroom areas, possibly with night purge.

Retail

Key issues:

Lighting contributes to more than 70% of the notional and actual total emissions so getting this right is the key to compliance.
Generally, retail buildings are the most difficult to make compliant with Part L.

Typical solutions:

Maximise the natural daylighting to help to reduce the lighting load.
Install an efficient lighting scheme and controls.

Making it real: how IES helps to achieve compliance

To achieve compliance with Part L 2006, a scheme must demonstrate it has achieved a reduction in CO2 emissions compared with the same scheme assessed using standards similar to those in the 2002 revision of Part L of the Building Regulations, known as the target CO2 emissions rate (TER). Which is where it starts to sound complicated…

The IES software uses three building models to prove compliance with the energy regulations:

The “notional” building is a version of the actual building that is modified to conform to standards similar to those in the Part L2 (2002) elemental methods, using a clearly defined set of standards relating to glazing area, construction and system characteristics. The notional building is subject to the same occupancy and plant operation patterns as the actual building.
The “actual” building is the building as designed but subject to standard patterns of occupancy and plant operation settings as defined in the national calculation method (NCM).
The “real” building is the building as designed with the occupancy and plant operation conditions expected to apply in reality.

To calculate the TER, the notional building is created to provide the benchmark against which the new building’s performance can be assessed to ensure it improves by a specified margin – a 28% cut in carbon emissions for an air-conditioned building and 23.5% for a naturally ventilated scheme.

The actual building is then modelled using standard NCM data but including the energy-saving elements in the real building, such as heat recovery and lighting controls. The CO2 emissions from the actual building are termed the building emission rate. It is the building emission rate that, for example, has to be 28% less than the TER for an air-conditioned building to prove compliance with Part L 2006.

IES compared the compliance calculation result for each building type with the relative significance of each building service within it. Example buildings, representative of the results obtained for each type, were selected to illustrate the differences between the types.

IES’s software works by allowing users to create the real building model from which to carry out their design calculations. When a compliance check is needed, the VE Compliance module automatically generates actual and notional models. NCM data is automatically assigned to the models, dependent on building location and type and room attributes. This data is standard across the different building types to provide a benchmark so comparative assessments can be made for compliance regardless of the specifics of real buildings.

The table (left) shows a selection of the NCM data used. There is a significant difference between the heating and cooling and other setpoints for different building types. The effect of this is to vary the significance of the energy contribution of each load.