Rainscreen Cladding & Curtain Walling
What is
Rainscreen and Curtain Walling
The Centre for Window and Cladding Technology (CWCT) standard for systemised building envelopes defines curtain walling as ‘a form of predominantly vertical building envelope which supports no load other than its own weight and the environmental forces which act upon it’.
Rainscreen cladding is a non-loadbearing external cladding and defined as ‘a wall comprising an outer skin of panels and an airtight insulated backing wall separated by a ventilated cavity. Some water may penetrate into the cavity but the rainscreen is intended to provide protection from direct rain’.
The distinction is that curtain walling is usually the whole envelope, while rainscreen cladding is the outer protective layer.
Rainscreen & Curtain Walling
What exactly is Rainscreen Cladding?
Rainscreen is a cladding system which comprises of an outer weather-resistant layer that is fixed back to the primary structure.
The outer layer is usually fixed using adjustable brackets which allows for the use of the insulation and breather membrane.
This is then fixed back to the primary structure and leaves a ventilated cavity which will differ in size depending upon exact compliance criteria.
What exactly is Curtain Walling?
Curtain walling is usually a lightweight non-loadbearing frame which wraps the building and separates the interior from the exterior.
Unlike rainscreen cladding, curtain walling panels are hung using sleeves and brackets and very much lend themselves to larger schemes with greater wall areas.
What types of finishes are available for these systems?
Why would I specify rainscreen cladding?
Why are these systems durable?
As neither system is load-bearing, this enables them to be produced from durable, low maintenance materials, (such as aluminium), whilst timber and masonry can suffer from discolouration, cracking and rapid aging.
Glass has an expected service life well in excess of 60 years whilst insulating glass (two or more glass window panes separated by a vacuum or gas-filled space to reduce heat transfer) has an expectancy of around 25 years.
What different types of Curtain Walling are there?
The classification of type of curtain walling can vary, but the most commonly used are:
Stick (Horizontal and vertical framing members, machined and cut to length in a factory and assembled on site).
Unitised (narrow storey-height units, pre-assembled in a factory)
Panellised (large pre-fabricated panels of bay width and storey height)
Spandrel panel ribbon glazing (a long or continuous run of units fixed between spandrel panels)
What should I know about cladding and fire performance?
Currently for buildings over 18 metres in height to the top storey floor, Euroclass A1 or A2 non-combustible materials must be used. Where you have a ventilated cavity, fire barriers should always be installed.
What is a ventilated or drained cavity in a rainscreen cladding system?
The ventilated or drained cavity is a requirement to allow for a constant circulation of air to allow any penetrating moisture to drain or evaporate and vent to the outside.
It is also important to remember that all insulation should be installed on the warm side of the façade and not the cold side of the vented cavity as this will make the insulation ineffectual.