Essential reading for anyone taking the Construction and Quantity Surveying pathway
This week the spotlight is on the Construction Technology and Environmental Services competency (T013). Here’s what the RICS Requirements and Competencies guide says about it:: ‘Candidates should have a clear understanding of the design and construction processes commonly used in the industry. They should have detailed knowledge of construction solutions relevant to their projects’.
This is a core competence under the Construction and Quantity Surveying pathway that must be achieved to level 3. To achieve competency level one, you should be able to ‘demonstrate knowledge and understanding of the principles of design and construction relating to your chosen field of practice’. At level two the candidate will be able ‘to apply their knowledge to the design and construction processes’. At level three you will have experience and be competent ‘to advise on the selection and application of particular processes within their area of experience. This should include liaison with specialists and consultants to develop project specific design and construction solutions’.
So you’ll need a wide range of knowledge and practical experience relating to your chosen field of practice. Lets look at an example of the type of question an assessor could ask at each level, relating to building technology and in particular mechanical services...
Question Can you outline the most common types of ventilation systems in a building?
Answer The common types of ventilation systems are:
• Natural ventilation
This describes the process of air entering and moving around a building by natural means and can be provided through;
- Openable windows; which are the most basic form of natural ventilation.
- Powered window actuators; which enable multiple windows to be controlled using a control strategy, e.g. the building management system (BMS). The windows can be programmed to open and close depending on the weather. Push button switches or hand held infrared remote control can also be used to power these actuators.
- Stack ventilation describes the process of warm air rising upwards through a building and leaving through high level openings. The air leaving the building causes cooler fresh air to enter the building through low level openings such as windows.
• Mixed mode ventilation
This describes a system which contains both natural and mechanical ventilation. The mechanical element is normally a supply only system; however an extract only or a supply and extract system can also be used. The mechanical element provides adequate airflow when natural ventilation is insufficient.
• Mechanical ventilation –Extract only
These systems are used in environments where the air becomes directly contaminated by a certain process or activity. These can be found in places such as toilets, kitchens and factories where they can offer consistent and reliable extraction.
• Mechanical Ventilation – Supply and Extract
This type of system includes a central air handling unit (AHU) normally containing air filters, along with separate supply and extract fans. With the addition of heating and cooling coils within the AHU the system has the ability to heat or cool air as required, while also having the option of heat recovery to improve energy efficiency. This allows some of the warm extracted air to be re-circulated into the supply, therefore reducing the amount of fresh air to be heated. A ductwork system is required to transport the air around the building.
Question Can you identify some of the issues to consider in the design of ventilation systems for buildings?
Answer The candidate may outline some of the following issues:
• Employer’s requirements – The chosen system and design needs to align with what the client wants to achieve from the project and the functional space requirements of the building.
• Occupant’s requirements – The range of internal conditions which the occupants are willing to tolerate.
• Cost –The budget available for the project and elemental analysis would need to be considered to determine how much is viable for the ventilation system. The whole life cost of the system should also be a major consideration.
• External conditions – The location of the building needs to be considered and may make natural ventilation wholly or partially un-feasible, e.g. noise and pollution levels and local weather conditions.
• Control – The level of control required will influence the design, e.g. if air needs to be extracted at a certain time from an area e.g. in a manufacturing plant.
• Space – The amount of plant and services space available for ductwork and air handling units.
• Depth of building –If the building is very deep, atriums can be introduced to get air through the building, otherwise mechanical systems will be required.
• Security – The location of the building, its purpose and contents will determine the level of security required. If a high level of security is needed then natural ventilation may not be feasible, or openable windows will need physical barriers such as grilles.
• Environmental issues – A certain BREEAM rating may be desired and may affect the choice of ventilation system. If a mechanical solution is necessary, factors such as the level (if any) of filtration required will be dependent on what items need to be discharged. Any contaminated substances will need to be filtered before they are discharged into the atmosphere.
Question On your project X, what ventilation system was used and how did you work with the team to ensure the most cost effective design solution was achieved?
Answer The answer will of course depend upon the candidate’s experience and the type of building they worked upon. The different systems vary greatly in cost with natural ventilation being the cheapest and mechanical ventilation (supply and extract) the most expensive. However, the chosen ventilation system needs to be fit for purpose and natural ventilation would not be suitable for a building such as a data centre, where there are high heat loads. The candidate should consider the design issues identified under level 2, meaning some ventilation systems would be unfeasible.
The mechanical system is an integral part of the overall building design and will have a knock on effect on most other building elements, including floor heights and plant space requirements. Therefore when considering the most cost effective solution it must be considered within the overall building context. The candidate would be able to outline their role in working closely with the design team through the design development to select the ventilation system(s) appropriate for the project. They would then be able to explain how they worked with the design team to get overall best value for money, taking into account the whole life cost. Some of the commercial issues to consider for mechanical systems are:
• Ductwork distribution through the building
• Builders work
• Fire strategy
• Exposed ductwork and plant (note, depending on location, this may result in increased cost of ductwork, although may save money overall through omitting ceiling finishes)
• Alternative types of insulation
• Open plan areas
• Avoiding over design and providing too high loads
• Location of plant relative to areas to be serviced
• Different ductwork profiles available (rectangle, circular, oval)
• Avoiding unnecessary controls
• Co-ordination with the building fabric, structure and other services to reduce risk.
Dean Mills, director, Turner & Townsend Cost Management
APC Trainer's advice is intended as guidance only and should not replace your own study