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Section 1 Optimum Solutions

Section 2 Feasibility Studies


Description:  The purpose of this unit is to enable you to analyse solutions to given building services related problems and to identify optimum solutions.

Author:  Gates MacBain Associates

Section 1  Optimum Solutions

Aims and Objectives

At the end of this section you should be able to:
  • Develop strategies for identifying optimum solutions.

This is in continuation to the units: Design Strategies; and Design Parameters in which we looked into identifying the client needs, developing design parameters and identifying sources of information to ascertain the reliability of these parameters. 

The design team then has to explore various options, asses their feasibility and identify the optimum solutions. In this unit, we will develop strategies to identify such solutions.   

Design process and relevant stages 

Once the client needs are identified, the design team maps these with the regulations, standards and codes of practice to establish design parameters. Concept designs are developed and checked for compliance with health and safety and other pertinent legislation.  

These processes can be mapped with both RIBA Plan of Work 2007 (Stage A, C & D) as well as with CIBSE Design Compass (Preliminary design stage). Following table will show this clearly. 

Building Services design stage - Preliminary design


RIBA Stage A

Assess options against client requirements, performance, water and energy use,


Preparation of feasibility studies and assessment of options to enable the client to decide whether to proceed

Select  proposed systems


RIBA Stage C



Preparation of Concept Design including outline proposals for building services systems.



RIBA Stage D



Development of concept design for building services systems.

Integrated Design Process   

It is an established fact that the best way to approach a design problem is to follow an integrated approach: the whole team works on the ‘whole’ building so that feasibility of proposals can be assessed objectively. The integrated design process works with the architecture, the design, functional aspects, energy consumption, indoor environment, technology, and construction   

In such a process, performance targets for a broad range of parameters are established. The approach which is followed is to minimise heating and cooling loads and maximise daylighting potential. This can be achieved through orientation, an efficient building envelope and consideration of amount, type, and location of fenestration   

These calculated loads are met with through the maximum use of solar and other renewable technologies without compromising  on performance targets such as indoor air quality, thermal comfort, illumination levels and noise control.   

The process is repeated to produce at least two or three concept designs. The most promising is chosen for further development.     

Building Information Modelling (BIM)   

BIM is a 3D modelling software which is intelligent enough to create optimised, efficient, and environmentally friendly building designs. The tool is useful in feasibility analysis of design proposals. It can be used in a truly integrated manner to ensure ‘fitness’ with the other services and building elements. The idea is that all professionals involved in the design including building services engineer work on the same model. For a building services engineer, BIM is useful in carrying out life-cycle cost analysis as well as analysis of energy systems and components. The tool is useful not only in feasibility analysis but also in evaluating final designs.     

Essential Features   

An ideal environment friendly design with adaptive capacity may include all or some of the following features:     

Building and building envelope   

In a good environmental design, orientation, form and layout of the building could be used to reduce the energy used in heating or cooling a building. This would require increased thermal efficiencies from building envelopes which would have an effect on the other choices such as roofs and façade.  

The approach is to minimise heating and cooling loads and maximise potential for daylighting. The arrangement, size and performance of the windows, glazing and façade systems, will impact on daylight and internal comfort. 

Operable shading devices should be used to allow more flexibility for the users.  


Natural or passive ventilation is to be used where possible. For such a system, dark coloured ducts should be used for extraction as these absorb heat from the sun and can help air inside the building rise up and out of the building. To draw fresh air, light coloured ducts should be used. 

Another option is low carbon mechanical ventilation. Using large extraction ducts can reduce air pressure so decreasing fan power.  

Thermal mass  

The thermal mass represents a building’s ability to store heat. A building structure can be used to act as a thermal storage which can help to cool the building. Thermal mass can be achieved by providing thicker walls or ceilings. However, location of these elements within a structure is important as this factor only may determine the effectiveness of thermal mass.  


Buildings will have to be provided with some form of mechanical cooling due to probable future climate changes. The building should have a combination of conventional air conditioning and passive cooling options. Such a system should operate ‘on-demand’ which means that mechanical option will come into play only when the passive features fail to achieve the required comfort levels.  

Green roofs  

Green roofs help to improve the comfort conditions in upper floors of a building by a significant reduction in roof top temperatures. These roofs also act as insulators and reduce noise. 

The resources listed contain a more detailed explanation of feasible and optimum solutions.  



  • Churcher, D. (2008) Design Activities and Drawing Definitions (BG 6/2009), 2nd edition. BSRIA
  • Longmaid, J (2004). A Practical Guide to system selection (BG 9/2004). BSRIA 
  • Pennycook, K. (2007). A Quality Control Framework (BG4/2007), 2nd edition. BSRIA

Self-Assessment Task

You are a design engineer for a mixed-use large complex building. 
  • Produce a list of essential features you would like to incorporate in the building.

Section 2  Feasibility Studies

Aims and Objectives

At the end of this section you should be able to:
  • Critically analyse feasible solutions to specified tasks and problems across a range of building services related subjects.

When we say that a project or a system is feasible, what do we really mean? The dictionary definition of feasibility is suitable, capable of being done, capable of being used, etc. In case of a building services design, the design team has to assess various design options available to them in terms of:  
  • Technical: Is the proposed system technically sound and fit-for-purpose?
  • Financial: Is the proposal in line with the budgetary constraints?
  • Performance in use: Will the proposed system perform as expected?
  • Environmental: What will be the impact of system operation and maintenance on the environment?
  • Health and safety issues: Is the proposed system complies with health and safety regulatory requirements during installation and while being maintained?
  • Energy use: What is the contribution of renewable (zero and low carbon) technologies and what is the overall energy performance of the proposed design?
  • Climate change: Is the proposed design has the adaptive capacity?

These questions are to be answered in the light of design brief/client needs, relevant legislation, standards and constraints and are effectively an assessment exercise and should include a series of consultations between the design team and the client. A brief outline of these aspects follows.  

Technical feasibility 

This includes considerations such as plant size, interaction among various services and how these fit into the other structural elements. These technical solutions should be mapped against client needs as research shows that though clients were complimentary regarding the technical soundness of installed services, these were not required. There may be more than one solution which are technically feasible. The design team should also consider issue of building in redundancy for future needs.  

Financial feasibility 

A costing exercise should be carried out for each option using whole life cycle approach and compared with the expected budgetary allocation. This includes that at times, cost can be an over-riding factor in final selection of a system.   

Performance in use 

The options should be assessed against acoustic, thermal and visual environments as detailed in the brief and as is suitable for the type of building and the business. BSRIA publication listed in the resources (BG 4/2007) list some examples of design errors and its implications.  

Environmental feasibility 

The options available should be compared in terms of their pollution potential during construction, operation and demolition, and their impact on water, energy, waste and materials resources. UK regulation compliance for new buildings is demonstrated by achieving better or equivalent carbon emissions performance (in kg CO²/m²/year) compared with a target emissions rate (TER).   

Health and Safety issues 

The options should be assessed against their potential to pose any un-necessary risks during installation, operation, maintenance, decommissioning and removal of proposed services. While doing so, designer should be aware that all these requirements carry equal weight.  

Energy use 

A part-to-whole approach should be adopted: taking each area and then aggregating it to get a clear picture. A whole building approach including HVAC options and lighting choices is proven to result in more efficient designs.  

Climate change 

The options should be assessed for their potential to cope with the possible climate changes and their effect on the building services. This simply means to assess how easy it would be to modify or replace the services.   

Optimum Solutions 

The dictionary definition of an optimum solution is ‘the one which best fits the situation and uses the resources in the most efficient manner’.

Based on the assessment of various options, the engineer should be able to identify the optimum solution which will satisfy client needs and will comply with standards and legislative requirements.  

The search for an optimum solution is necessarily an integrated design exercise. Integrated design solutions where building elements together with service functions are integrated into one system to reach an optimal environmental and cost performance. 

Hence an optimum solution might involve optimising the building’s standard components such as windows, walls, floors, etc. alongside HVAC and electrical systems to minimise size, waste and energy use.   

Design Options  

While carrying out the feasibility analysis, the engineer would be face with making choices among the various options available which have to be benchmarked against the performance criteria and other factors as described earlier. The options are discussed below. Please note that this is not an exhaustive list.  

Heating, ventilating and Air-Conditioning (HVAC) 

The options available might include: natural or mechanical ventilation; passive solar systems, use of renewable technologies; and zoning options.For the heating system, the choices have to be made about the system and source of energy such as: standard gas boilers, heat pump; Ground source heat pumps; mechanical pumps, etc. The coefficient of performance (COP) is a good tool to indicate the performance  

Lighting and electrical 

The engineer should assess various glazing and shading options in order to control glare and solar gains. Possible interactions of lighting with other services such as internal heat gains from lighting when calculating the heating and cooling loads, the effect of solar control on the natural ventilation flow, etc. should also be examined. With the help of energy calculations, optimum control solutions could be identified to achieve maximum energy savings.   

Public Health 

For public health, the options include: Water collection, treatment and distribution systems; hot and cold distribution systems, reclaimed water systems, green roofs, SUDS, etc.  

LZC technologies 

For low and zero carbon technologies (LZC), potential impacts of future developments of the surrounding area should be taken into account such as future high buildings that could affect solar & daylight availability, etc.   

A combination of systems is likely to result in an efficient design.   

The resources listed contain a more detailed explanation of feasible and optimum solutions.



  • Churcher, D. (2008) Design Activities and Drawing Definitions (BG 6/2009), 2nd edition. BSRIA
  • Longmaid, J (2004). A Practical Guide to system selection (BG 9/2004). BSRIA 
  • Pennycook, K. (2007). A Quality Control Framework (BG4/2007), 2nd edition. BSRIA

Self-Assessment Task

  • Describe how you would justify your choice of the system in the previous section to the client.

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