Glass facades, curtain walls and prefabricated facade systems

The facade is one of the most technically complex elements in modern buildings. It functions both as the building envelope, an architectural element and a technical interface between the indoor and outdoor environment.

At the same time, the requirements for facades have increased significantly in recent years.
Energy consumption, documented CO₂ impact, fire safety, indoor climate and durability all play an important role in the design process.

For architects, consultants, contractors and developers, this means that the choice of facade today is no longer only about architectural expression.
It is equally about buildability, technical documentation and long-term performance.

In this article we cover:

• the most commonly used facade types in modern construction

• technical aspects such as U-values and thermal bridges

• the differences between stick-built curtain walls and prefabricated facades

• the importance of installation principles and tolerances

• how facades influence the building’s overall carbon footprint

What is a facade?

A facade forms the external building envelope and separates the indoor environment from the outdoor climate.

It has three primary functions.

Protection from weather

The facade protects the building against rain, wind and temperature fluctuations.

Energy performance

The facade plays a major role in the building’s energy consumption through insulation performance, glazing areas and airtightness.

Architectural identity

The facade is often the element that defines the visual character of a building.

A facade typically consists of several layers:

• structural frame

• insulation

• air and vapour barriers

• facade cladding

• windows or glazing units

• joints and sealing systems

The interaction between these layers is crucial for energy performance, durability and maintenance.

Types of facades

Modern buildings typically use three main facade principles.

Glass facades and curtain walls

Glass facades are widely used in office buildings, institutions and commercial developments.

In these systems the facade consists of aluminium profiles where glazing units and panels are installed between vertical mullions and horizontal transoms.

This construction type is commonly referred to as a curtain wall or stick-built facade, because it is assembled element by element directly on the construction site.

Advantages

• high level of design flexibility

• adaptable during construction

• suitable for large glazed areas

Disadvantages

• installation takes place on site

• longer construction periods

• greater dependency on weather conditions

Prefabricated facades

In many modern construction projects, prefabricated facade elements are increasingly used.

In this approach, facade elements are manufactured in a factory and delivered to site as finished modules.

Systems such as HansenUnitAl is an example of this type of solution.

The facade elements are produced under controlled conditions and installed directly onto the building structure.

This method moves a large portion of the labour from the construction site to the factory.

Typical advantages include:

• consistent quality

• faster installation

• reduced complexity on site

• earlier completion of the building envelope

Technical aspects of facade design

When designing facades, several technical factors significantly influence the building’s performance.

U-values and thermal performance

The U-value describes the rate of heat transfer through a building element.

For facades, the U-value depends on factors such as:

• glazing configuration

• thermal performance of the profiles

• spacer systems

• joint details

Even small changes in profile design can affect the overall energy performance.

Thermal bridges in facades

Thermal bridges typically occur at transitions between different building components.

In facade systems they are often found at:

• joints between facade elements

• connections between the facade and floor slabs

• fixings to the structural frame

If thermal bridges are not handled correctly, they can lead to increased heat loss and risk of condensation.

For this reason, careful detailing is essential in modern facade design.

Airtightness

Airtightness is a key factor in building energy performance.

Air leakage can result in:

• increased heat loss

• draught and reduced comfort

• moisture transport within the construction

Modern facade systems therefore rely on tested assemblies and documented joint solutions.

Design coordination and buildability

Facades are one of the building elements where design and construction are closely linked.

If the facade is not designed with installation and tolerances in mind, problems can occur during construction.

Tolerances

Structural frames always contain geometric tolerances.

Facade systems must therefore accommodate variations in:

• floor slabs

• columns

• concrete edges

This is typically achieved through adjustable brackets and fixing systems.

Installation principles

Installation methods vary depending on the facade type.

Stick-built curtain walls are usually assembled profile by profile.

Prefabricated facades, by contrast, are installed as complete modules.

This method significantly reduces on-site installation work and can shorten the construction programme.

Sustainability and facades

Facades play a major role in the environmental impact of buildings.

Today this is typically assessed through life cycle assessment (LCA) calculations.

Material choices and facade construction influence factors such as:

• CO₂ footprint

• resource consumption

• waste generation

• service life

Prefabricated facade elements  can often reduce resource consumption because production processes can be optimised and material waste minimised.

Operation and maintenance

Facades are continuously exposed to wind, rain, temperature changes and UV radiation.

For this reason, regular inspection and maintenance are essential.

Typical maintenance activities include:

• inspection of fittings and hinges

• checking sealing gaskets

• cleaning drainage systems

• inspection of glazing and sealants

Regular service can extend the lifespan of the facade and prevent more significant damage.

The future of facades

Facade technology is developing rapidly and three trends are shaping the industry.

Increased prefabrication

More facade elements are manufactured industrially.

Greater focus on climate impact

Material selection and construction are increasingly optimised through LCA.

Digital design and coordination

Facades are increasingly modelled digitally, allowing optimisation of energy performance, structure and installation already in the design phase.