The Tender Analysis
Quotations received from multiple Subcontractors invariably have differences and it’s important to make sure you’re comparing Apples with Apples. Look out for these important ‘cross-checks’ to make sure you’re comparing like-for-like proposals.
1) Rain rejection performance
Louvres should be tested & rated in accordance with EN13030:2001. This will give an effectiveness class from A to D at various different airflow velocities. Quotations should be checked to ensure that the louvre performance is in line with the specification and so that quotes are like for like.
2) Aerodynamic performance
When air is drawn through a louvre this creates a pressure loss which affects the operation of the building’s ventilation system. It is important to check that the louvre will not cause too high a pressure drop when operating at the design airflow velocity. Sometimes this information is not provided in the architectural specification and needs to be sought from the M&E team. Aerodynamic performance Class ranges from 1 to 4 with 1 being the least restrictive to airflow and 4 being the most restrictive. Keep an eye out for this in all tender submissions.
3) Acoustic rating
Most weather louvres are not designed to reduce noise and will not assist in the control of noise in or out of a building. Acoustic louvres are different products which contain acoustic media in between the blades to attenuate noise as the air flows through. These acoustic louvres are usually much heavier, deeper and have wider air gaps between the blades and therefore, are much more costly.
4) Bird mesh / insect mesh screens
Many specifications will call for a mesh screen to be incorporated behind the louvre to prevent vermin ingress to the building. These mesh screens can come in many different materials, grades and finishes. The presence of a mesh can also impact the aerodynamic properties of the louvre if it’s different from the mesh that was used in the EN13030 test. Be sure to check this out and ensure you’re compliant with the specification still.
5) Surface finish
Check that the correct finish has been included for. Usually Polyester powder coating or anodising will be specified for aluminium louvres. Ensure that the correct film thicknesses & coating specification has been included.
6) Modular or continuous line louvres?
Many weather louvre systems are capable of being installed as continuous banks or “walls” of louvres without visible blade joints. Some architects prefer the look of a unitised or modular appearance and may want to see the frames of the louvre system expressed – for example, to line up with grid lines or mullions of a curtain wall system above or below. This can have a significant impact on the cost & method of installation.
This next Chapter identifies six simple, intelligent solutions to Value Engineer a Louvre package…
1) Is Class A weather protection necessary?
Most Class A louvres are double-bank systems and will be more expensive than standard single bank louvres. Class A louvres are needed for critical areas such as electrical switch-rooms and fresh air inlets to furnished rooms. For most plant room applications or where the louvre is connected to ductwork, standard single bank louvres will be adequate and can be far more cost effective.
2) Is a bird guard really needed?
Many louvres are installed as screens to open top roof plant compounds and therefore, bird guards are not a necessity. Omit guards in these areas to make a saving.
3) Is insect mesh really needed?
Insect mesh has a lower free area than bird mesh and consequently the louvre area will need to be increased in order to keep the pressure loss down to a reasonable level. Also, insect mesh will clog up with dirt very quickly and will need to be cleaned regularly – avoid unless insects have been identified as a particular problem for your project.
4) Is a modular appearance necessary?
Continuous line louvres can be more economical as there is less off-site assembly work to do, fewer frame components, reduced transport costs and often quicker installation times. Where possible focus on this as a solution to create savings.
5) Primary / Secondary steelwork considerations
Many louvre subcontracts include for the supplier to provide their own steelwork supports; however, if the primary supports can be procured via the steelwork contractor this is likely to be more economical. The louvre subcontractor will generally provide their own secondary steelwork braces and connection brackets but would subcontract primary supports at a higher cost.
6) Anodising Vs PPC?
Some coloured anodising systems can be very expensive and there are very good Polyester Powder Coat alternatives. Anodising can also be quite restrictive for some manufacturing processes and PPC is more flexible as it can be applied after fabrication of components. Where possible, consider PPC as a viable and cheaper alternative.
Louvres are a package of works that tends to fall on the critical path of the project given their inclusion as part of the building envelope. Given their discrete and minor nature, quite often less attention is paid to them than should be – often to the detriment of the project!
Don’t make this mistake and follow these six tips for a snag free handover:
1) Coordination Meetings
To be arranged between louvre contractor and the M&E contractor prior to the placing of any orders and during the design stage to ensure louvre dimensions are agreed and finalised early. This should allow for an issue-free installation.
Finalise and agree the scope of any support steelwork to be included within the louvre package. Agree details of connections to the primary steelwork and if possible incorporate bolting holes and / or connection lugs into the primary steel package to avoid site drilling of finished steelwork. The louvre subcontractor should provide a builders-work drawing showing their requirements and this will save time on site.
Can the louvre subcontractor use the same access system as the façade contractor? Consider shared access schemes to avoid double the site setup time and costs.
Often it’s difficult to secure correx type sheeting onto an open louvre system due to lack of contact surface for tape and high open area. Consider leaving some louvre blades out until just before PC in high traffic areas to prevent damage which can be costly at the back end of the programme.
Consider how the louvres will be accessed for cleaning prior to Practical Completion. Is the clean to be part of the louvre package or a general building clean? Louvres can become dirty quickly once in operation and also during the construction phase. Consider allowing beneficial use of the BMU prior to PC to avoid contractors having to bring back their own access equipment.
This content was created in collaboration with Emtec. Emtec is a specialist acoustic contractor with a wealth of experience gained by solving noise and vibration problems across a wide range of industries. Their experienced engineers work closely with customers to configure bespoke acoustic solutions, tailor-made to each project’s exact requirements.