CPD: Metal ceilings
This CPD module takes a look at the design of suspended metal ceilings
This CPD module, sponsored by SAS International, takes a look at the design, specification, integration and performance of suspended metal ceilings across the Middle East
Ceilings are an element that is often undervalued by the occupants of a building. However, they play an important role in their comfort. Meeting occupant demands for a modern office environment requires consideration to be given to acoustics and space flexibility.
Low maintenance costs and product durability are factors that also need to be addressed, while architects and clients will be looking for the optimum aesthetic finish. Suspended ceilings are traditionally installed to provide acoustic comfort and service integration.
The choice of tile provides the desired acoustic performance. Metal ceiling tiles are supplied with factory-formed apertures for luminaires and other services, reducing on-site waste and installation time. Engineered systems can also ensure that product quality is significantly better. Working closely with project teams and coordinating service options, prefabrication can lead to on-site cost savings.
There are a number of different design and performance options that need to be considered when specifying a ceiling, including:
Material typE: A range of different ceiling materials are available on the market, including mineral wool, gypsum and metal. In addition to meeting the requirements of LEED and Estidama, the long-term environmental benefits of metal meet the sustainability demands of modern projects. With a 25-year lifecycle and minimal ongoing maintenance, metal provides the durability that clients want.
It is specified on numerous construction projects for its performance and, unlike other materials, it has a closed lifecycle loop, as it can be recycled into new steel. With 40% recycled content, steel is the most recycled material globally.
Offering significant value to the client, there are no disposal costs at end-of-life, with a retained residual value contributing toward future refurbishment.
Steel can be used for applications such as cladding, soffits and ceilings, especially in locations where humidity and proximity to the sea must be considered. Steel is being supplied to projects in the region because of its durable and versatile qualities, which offer a cost-effective and sustainable solution. It can withstand weathering and, applied with a powder paint coating, is guaranteed for 40 years.
The leading suspended ceiling manufacturers are able to provide full ISO 14025 Environmental Product Declarations for their ceiling systems.
Acoustic Performance (Figure 1): The versatility of metal provides unrivalled acoustic properties while maintaining a continuous aesthetic appearance. A number of different acoustic backing materials can be used with perforated metal panels, providing acoustic attenuation of up to 49dB and acoustic absorption of 0.90.
To provide the ideal levels of occupant comfort, it is important to ensure the correct acoustic performance is specified and installed. On many projects this will include a mix of sound-absorbing tiles in open-plan spaces and sound attenuation tiles for modular offices.
Sound Absorption (Fig 2):
Acoustic absorption is a measure of the ability of a surface to absorb sound, minimising the amount of sound reflected back into a space. High-performing acoustic pads installed in the rear of a perforated metal tile can overcome this reflected noise within an environment. Tested under BS EN ISO 11654, the results are reported in three different ways as:
• Sound Absorption Rating:
A single-figure rating, quoted as , based upon octave frequency bands, ranging from 0.0 for total reflection, to 1.0 for total absorption.
• Sound Absorption Class (Figure 3):
There are five categories of sound absorption, ranging from Class A to Class E, with Class A offering the higher level of sound absorption. Sound Absorption Class can be roughly equated to the value of .
• NRC – Noise Reduction Coefficient
A more traditional method of defining sound absorption is Noise Reduction Coefficient (NRC), which is an arithmetic average of octave band absorption over a limited frequency range.
Sound Attenuation / Insulation (Fig 4): Acoustic attenuation is used to describe the reduction in sound between two spaces separated by a dividing element – for example, a wall or partition between two rooms.
Sound attenuation is measured in accordance with BS EN ISO 140, defined in BS EN ISO 717.
Performance is assessed in terms of third octave band values, with a weighted single figure given to allow ease of comparison.
Perforations: They play the most important role in providing acoustic comfort; there are many different perforation patterns available, with varying degrees of open area from 2% to 65%. Larger perforations can allow heating and cooling products to be installed behind the ceiling, leaving a clean flush finish.
The size and pattern of perforations within the tile face also contributes to the overall acoustic performance of the tile, with an optimum free area range of between 15% to 22%.
Finish: Metal ceiling tiles are generally finished with a polyester powder coating, applied post-fabrication to prevent rusting.
Tiles are generally supplied with a smooth finish in RAL 9010, White, with a 20% gloss. Alternatively, they can be specified with a number of different finishes, including fine-textured, anti-bacterial and anti-microbial, galvanised and wood effect.
Integration: The way products integrate with ceiling systems plays an important part in any ceiling design. Building services can be incorporated into a ceiling, and each of these can require apertures to be formed in a tile.
The ceiling also integrates with structural elements of the building, including walls and columns. A number of design options are available to meet any integration requirement. Apertures are generally formed during manufacture for luminaires and other services, reducing on-site waste and installation time. By integrating these products efficiently, cost- and time-savings can be made on projects.
Accessibility and Maintenance: With the number of services that are present in a ceiling void, there is a need for regular access without causing tile damage. The frequency of access is dependent on the environment and the number of services included. A range of ceiling access options are available using different ceiling systems.
Metal ceiling tiles are maintained using a simple mild detergent diluted in warm water. The frequency of cleaning is dependent on the environment, function and application within the building.
Durability: Ceilings need to be extremely robust. Claims made by some suppliers as to the suitability of their products and technical composition for cleaning varies. Unlike other suspended ceilings, metal ceiling tiles are not limited to a fixed number of wash cycles, and can be cleaned regularly. With a 25-year product life guarantee, the costs associated with metal tiles are significantly lower.
Type of metal ceiling systems:
When designing for any project, different options can affect the aesthetic finish of a suspended ceiling, complementing and reflecting other architectural features.
It is not necessary to take a ‘best-fit’ solution; each ceiling is different and requires a tailored approach; projects and buildings are not always square; demands from users vary, and have to be taken into account.
The majority of ceiling systems either have a concealed or exposed grid. Exposed grids can be flush with the ceiling plane or recessed; tiles can be modular or manufactured to planning modules. Concealed grids can produce a monolithic ceiling plane.
Clip-in Tiles (Figure 5): With ease of cleaning and secure ceiling voids, SAS System 150 clip-in tiles are ideal for hygienic environments and public spaces where void security is a requirement. Tiles, available in 600 x 600mm or 1,200 x 300mm, are supported by a concealed suspension grid, and can be demounted from the grid or hinged downwards. As upward pressure can be applied, strict cleaning schedules, including deep steam cleans, can be adhered to.
Lay-in Tiles (Figure 6): Traditional modular lay-in tiles, SAS System 130, can be customised by utilising differing grid options. Tiles are generally provided in 600 x 600mm cassette form, complete with acoustic fleece and pad.
The range of grid options includes traditional tee grid to flush aluminium finishes, with tiles laid directly in. Providing flexibility for locating partitioning, a linear thread form allows partitioning heads to be fixed without causing any damage to the ceiling plane.
Linear and Tartan Grid Tiles (Figure 7): Offering the facility to manufacture tiles in millimetre increments and mega panels, sizes up to 1,500 x 1,500mm, SAS System 330 provides functionality and outstanding performance with a range of cost-effective design options.
This system is ideal for offices - both new and refurbishments - due to their ability to meet any building’s grid size.
To meet the necessary design requirements, the supporting profile and tiles can be provided in a range of shapes to allow waveform or radial designs to be created.
Bespoke Ceilings: Building/ceiling design is not limited to square and rectangular; radial, vaulted and even waveform ceiling design can be accommodated. Bespoke ceilings can be visually effective while maximising space.
Working with a manufacturer
Understanding that all projects are unique, many manufacturers ensure solutions provide for the long-term while meeting environmental credentials and offering greater design flexibility. If architects and contractors work closely with manufacturers, it is easier to ensure their design and performance specifications are met.
Having read this CPD module and made use of the references, you should be ready to select the correct answer to each question below:
1) What is the typical product life guarantee you would associate with a metal ceiling tile?
a) 5 years
b) 25 years
c) 10 years
2) What dB level of acoustic attenuation can you achieve with a metal ceiling tile?
3) What is the optimum acoustic open free area for perforated metal tiles?
a) 15% - 22%
b) 2% - 65%
c) 30% - 41%
4) How long can the polyester powder paint finish be guaranteed for?
a) 5 years
b) 25 years
c) 40 years
5) What is the average global recycled content figure for steel?
Your answers to this CPD module should be sent via email to Kirsty Bird, CIOB. Email: firstname.lastname@example.org