Colt Louvre: Understanding louvre systems

How 3UL Works Diagram
How 3UL Works Diagram

Specifying louvre systems is always a compromise, and requires some judgement to take into account the particular needs of each application. At one end of the scale for example a car park may require maximum ventilation but little protection from rain penetration. Alternatively, a plant room containing special machinery or electrical equipment may still need high levels of ventilation but with maximum protection from water entry.

The ideal design solution is to produce a louvre system that offers the best rain defence and aerodynamic performance.

Unfortunately this seems to be unachievable. But nothing matches the overall performance standards set by the Colt Universal Louvre range.

Screening Louvre

1UL Universal Louvre installed at Evilinas Hospital
1UL Universal Louvre installed at Evilinas Hospital

The principal objective of screening louvres is to obstruct line of sight from normal vantage points by virtue of its design or orientation. Generally each run of louvre will have a continuous appearance to blend in with the building. Universal Louvre can also be made to provide a contrast to the building as an architectural feature.

Whilst the screening application is certainly the simplest from a performance perspective, it is arguably the most demanding from the viewpoint of aesthetics and configuration.

Colt 1UL Universal Louvre systems (a single bank 50mm or 100mm pitch roll-formed louvre) allow maximum airflow with minimum resistance and are ideal for screening areas such as plant rooms and car parks.

Design considerations include:

  • What building elements do I want to hide?
  • Do I want the louvre to blend into the surrounding building structure?
  • Do I want the louvre to be a feature on my building?
  • What effect do I want to create?
  • What material and finish do I need?
  • Do I need to maximise light entry through the louvre system?
  • Should louvre blades be inverted?

Ventilation (or Performance) Louvre

2UL at Royal Mail sorting office, Northampton
2UL at Royal Mail sorting office, Northampton

The principal objective of Ventilation (or Performance) Louvre systems is to allow the passage of air, whilst providing a measure of protection against the rain.

Specifying performance has not been helped by conflicting technical information given by louvre manufacturers which quotes percentage free areas measured in different ways, namely as resistance to airflow and aerodynamic coefficients alternatively.

Design considerations include:

  • Site location and exposure
  • Severity of local (site) weather conditions
  • Location and exposure of louvres on building
  • Airflow rate and direction through louvre
  • Maximum acceptable pressure drop
  • Degree and depth of water penetration acceptable
  • Special solutions for sloping applications

For a true comparison of performance, the aerodynamic coefficient and the degree of rain defence effectiveness are the only sensible measures. These have been included as part of the HEVAC 4th Edition test standard, which includes a simple classification system.

Colt offers two types of performance louvre: a double bank 50mm pitch roll-formed 2UL - Universal Louvre and a triple bank 50mm pitch roll-formed 3UL - Universal Louvre.

Colt UL louvre selection program

“UL Select” is an Excel sheet which enables users to make their own selection of Colt louvre systems based on the weathering classification and aerodynamic performance required for the system. If the area of louvre or the airflow is known, the program provides the pressure drop. If the flow rate and the maximum pressure drop are known, the program provides the minimum size of louvre. Click here to access it.

Colt International offers the following services:

  • Scheme design
  • Provision of performance specifications
  • Project management
  • Supply
  • Installation, commissioning and maintenance of systems