Understanding Lux Level Requirements for Commercial Lighting Design

Lighting design plays a key role in commercial buildings which are typically used by people to perform a task or conduct an activity. To achieve their tasks or activities in a workspace, the right amount of illuminance is necessary, over-lighting is as much as a hindrance to accomplishing tasks as under-lighting. Commercial lighting compared to industrial or residential lighting involves higher initial costs, higher maintenance, longer durability and lifespan and higher service costs. To identify the illumination level requirements or lux level requirements of a commercial building, it would be useful to understand the units of measurement of illuminance, the intensity or amount of light and the efficacy of the relationship between lux and lumen.

Illuminance or lux is the intensity of the level of light and ‘luminous flux’ or lumen is the amount of light produced. Lux is the unit of measurement usually measured in foot candles, one lumen is the measurement of the intensity of the light output and is equal to one lux across an area of one square meter. Given an area you may need to illuminate, the measurement of lux helps you identify the output or lumen required. Typically, for an office which is brightly lit around 400 lux of illumination is required and an office space which uses 100W incandescent bulbs in ceiling panels would produce 1600 lumens as the output of light. When a lighting design company designs light fixtures for a large commercial area, the number of light fixtures is usually increased to get higher lumen keeping in mind the lux level requirements.

A primary factor in ensuring efficiency in light design is achieved by balancing lux and watts or managing the amount of power used to produce light. The measurement of energy efficiency or the power required for light fixtures (luminaires) to operate is known as watts or wattage. The rate at which a light fixture converts power to light or watts to lumen is known as luminous efficacy and measured in lumens per watt (LPW). Typically, an office or commercial space with ceiling panels which would use 32W T5 or T8 fluorescent lamps would usually produce 50 lumens/watt.

Lux level requirements are calculated to determine the appropriate number of lights, the type of light fixtures and the best possible commercial lighting solution, based on the size of the office or commercial space, the type of task or activity which will be conducted and the energy efficiency standards required.

In most cases, based on the client requirements of lux levels, office spaces are over-lit and are usually more than rates mentioned in the lighting standard codes and guidelines developed by professional lighting bodies. Lighting consultants and MEP engineering design teams while keeping in mind client requirements must also consider lighting codes and guidelines which mention the minimum lux level requirements that need to be maintained. Several lighting professional bodies have published handbooks and guidelines, some of which include lighting guides published by the Chartered Institution of Building Services Engineers (CIBSE) in the UK, the IESNA Lighting Handbook by the Illuminating Engineering Society of North America and guides and lighting codes provided by the Lighting Council Australia.

To improve energy efficiency and reduce consumption, several countries have presented lighting codes and green building solutions which have made lighting manufacturers develop higher energy efficient light fittings. For offices and commercial spaces, the stipulated lighting watts/m2 is considered to be within the range of 10 to 15 watts/m2. With the increase in the use of LED light fixtures, lighting consultants are required to maintain lighting watts within the range of 5 to 8 watts/m2, while maintaining lux level requirements.

To ensure commercial lighting designs provide higher energy efficiency, lower energy consumption and better control on energy usage, lighting consultants and MEP engineering design teams must consider trending lighting solutions in the industry. From LED fixtures with advanced lighting controls, energy harvesting technologies, interactive lighting to connected lighting, there are several trends which a lighting design company could use to provide high energy-efficiency and customer-centricity in lighting design solutions for commercial spaces.

Why MEP Contractors Change MEP Design Models

In the MEP environment, a building’s MEP designs are initially developed at high level and then detailed to make them clash free and installation ready. MEP designers/consultants play a significant role in design decisions, construction planning, cost estimation and documentation. While design development is typically the role of the consultant and design detailing is done by the MEP contractor, when using MEP (M&E) BIM models and Revit BIM libraries, contractors invariably need to make changes to the MEP design model created by the consultant. 

To make a design installation ready, contractors may have to make several changes to the design-intent such as resizing of ducts, re-routing of pipework, adding wall penetrations, bolt locations and datum points for hangars and changing equipment. Once these changes are made by the contractor, the design would be installation ready and will need to be approved by the MEP consultant. The question that this article seeks to answer is why do MEP contractors need to make these and other changes to MEP design models?

• To adjust invert elevations – During the installation of plumbing or drainage pipes, MEP contractors deal with the point of the bottom inside of the pipe, this is known as the invert elevations. To guide pipe design and match the invert elevation height, elevation information can be vertically adjusted at the centre of the pipe using Revit. However, if you are unaware that the elevation information is in centre of the pipe, it could cause confusion in adjusting invert elevations and create discrepancies while coordinating with other disciplines. This is the reason why MEP contractors need to manually adjust invert levels, create spot elevations for the inside bottom of the pipe and change the design models to install pipes which are coordinated with other disciplines. 
• To retrofit MEP systems into a prefabricated module environment – Planning for prefabrication of MEP components into the 3D model would not be considered by designers and therefore the contractor is the party who will make adjustments to services to allow them to fit into prefabricated modules to maximise the advantages that are gained from off-site fabrication. In several MEP projects which require prefabrication of risers, ceilings and plant room areas, MEP services drawings and modules specifically for fabricators and installers is necessary to facilitate proper installation. MEP contractors make changes in the MEP design model to ensure that services fit within modules within the ceiling or riser space to allow prefabrication of MEP components off-site allowing faster installation on-site.
• To facilitate efficient spatial coordination – When installing MEP systems, effective spatial coordination with other building services and disciplines is imperative. A consultant may leave clashes in a model as his focus will be on getting a design issue by a due date. A contractor is more concerned with actual fitting so after conducting a clash test on the 3d model, MEP contractors will invariably change design models to ensure that all services are not clashing. The installation programme of the MEP system depends on clash free layouts and MEP contractors must make sure that MEP systems are spatially coordinated with other disciplines in the 3D model before creating M&E (MEP) Coordinated Drawings.
• To deal with constructability issues – There are several factors that influence the constructability or sequence in which MEP systems are installed. Some of the conflicts that require a change in MEP design include routing, fitting and sequencing of large equipment within a given space, conflicting piping network and installation of MEP systems within a crowded space. As MEP contractors need to tackle several conflicts and constructability issues before installing MEP systems, a change in MEP design usually occurs. 
• To install MEP systems economically and efficiently – While the MEP design intent may seem to be perfectly coordinated, it need not necessarily be economic or efficient when it involves installation. There are several costs involved when changes need to be made after installation such as re-routing pipes to reduce bends, re-positioning ducts to allow supply and extract in the correct locations, changing equipment or adding wall penetrations, bolt locations and datum points for hangars. To make sure that MEP systems are installed economically and efficiently, MEP contractors must make changes to MEP design models.
• Changes in materials and components – In some cases the MEP model from a consultant is accurately modelled with specified parts, materials and components. However, in some cases projects do not have specified parts and a consultant may use library elements from Revit leaving the contractor to update the model using his planned procurement schedule. This will result in changes due to sizes and access requirements for new components such as a change from copper to plastic pipe which is thicker or a change from one set of pumps to another that may be larger and may have different valve arrangements. The knock-on effect of such component changes can mean that other systems also need to be changed. 

Given the many reasons why MEP contractors need to change MEP designs and with the adoption of MEP (M&E) BIM practices, there is an overlap in the scope of MEP contractors and consultants during the planning phase. To know more about how you can reduce the duplication of efforts, additional costs, manage project schedules and reduce scope overlap, read more in this post to find out the possible routes that can be taken.

To ensure MEP design models are installation ready for MEP contractors to use on site, a viable solution would be to work with a 3D BIM coordination specialist or MEP engineering design service provider. At XS CAD, our experienced team of MEP designers in India provide BIM support and spatially coordinated building services drawings for key stakeholders in the MEP (M&E) industry, from MEP (M&E) consulting engineers and MEP (M&E) building services contractors. In our spatially coordinated MEP building services models, we use the latest 3D MEP (M&E) modelling software (Revit MEP) and clash detection technology (Autodesk Navisworks) to provide 3D M&E (MEP) coordinated drawings which adhere to engineering standards, the structural and architectural elements within a building.