How to Specify Architectural Louvres

Specifying Louvres on free area alone can cause serious problems:

The principle reason for using Louvres is to move air. How do you know if the Louvre you specify will actually deliver the air volume the engineer asked for? History has shown that sizing and specifying Louvres on free area alone can cause problems for architects and owners.

When you specify a 50% free area Louvre, what are you actually getting?

The reality is that other factors also impact  airflow, not just the free area, for example Louvre frames can add resistance to airflow. Mullions, structural supports, bird screens and insect screens also reduce airflow.

A more efficient specification solution is based on the needs of the building. It is therefore important to consider the following when specifying Louvres:

• 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
• Aesthetics of the building

Example NBS Style Louvre Specification

To be read with Preliminaries / General Conditions

GENERAL

110 Evidence of Performance

Certification: Provide independently certified evidence that all incorporated components comply with specified performance requirements

120 Site Dimensions

Procedure: before starting work on designated items, take site dimensions, record on shop drawings and use to ensure accurate fabrication

PRODUCTS

650 Metal Louvres

• Manufacturer: Construction Specialties (UK) Limited, 1010 Westcott Venture Park, Westcott, Aylesbury, Bucks, HP18 0XB
• Tel: +44 (0)1296 652800
• Fax: +44 (0)1296 652888
• Web: www.c-sgroup.co.uk
• Email: info@c-sgroup.co.uk
• Product Reference: CS 127mm Deep Storm Resistant Fixed Performance Louvre Model RSH 5700
• Materials: Heads, Sills, Jambs and mullions to be one-piece structural aluminium members with integral caulking slot and retaining beads. Mullions shall be sliding interlock type. Blades to be one-piece aluminium extrusions with front lip gutter and multiple secondary gutters designed to catch and direct water to sill. Louvres to be supplied with 102mm high by full depth sill flashings formed from minimum 1.27mm thick aluminium. Sill flashings to have welded side panels.
• Louvres and sill flashings to be as follows: Heads, Sills, Jambs and Mullions: Minimum of 1.91mm.  Fixed blades: 1.52mm
• Fabrication: Louvres to be mechanically assembled using stainless steel or aluminium fasteners
• Finish: Polyester Powder Coating – Colour: RAL 9003
• Size: As per elevation drawings and Louvre schedule
• Number of Louvre banks: Integrated slim-line double bank to give tangential separation
• Louvre blade pitch and angle: 50mm at Zero Degrees
• Performance Requirements: Louvres to be extruded to give an aerodynamically efficient profile to create tangential separation of water in airflow. Louvre to be mechanically fastened within extruded framing sections complete with integral channels to achieve maximum drainage. The system shall achieve a minimum Discharge Loss Coefficient of 0.320 and when tested in accordance with the principles of BS EN 13030:2001 (at 13m/s wind speed) will achieve the following Penetration Classes: A at 1m/s,  A at 3m/s and C at 5m/s
• Blanking Panels: As per drawings, schedules and M&E requirements
• Installation: Louvre to be installed by competent installer, strictly in accordance with manufacturer’s instructions back to primary steel structure