Thermal performance of steel-framed prefabricated buildings

Pre-engineered steel buildings find widespread applications across various industries due to their versatility, durability, and cost-effectiveness. Common uses for these structures include warehouses and industrial facilities, where their large clear spans and customisable designs provide ample space for storage, manufacturing, and logistics operations. Additionally, pre-engineered steel buildings are popular choices for agricultural purposes, serving as barns, equipment storage, and livestock shelters.

In the commercial sector, they are utilised for retail spaces, offices, and recreational facilities, taking advantage of their quick construction time and design flexibility. The resilience of steel against environmental elements makes pre-engineered steel buildings suitable for aircraft hangars, providing secure housing for aeroplanes and related equipment. Moreover, these structures are employed in educational and institutional settings, such as schools, gyms, and community centres, owing to their ability to accommodate large, open interiors. Overall, pre-engineered steel buildings serve as versatile solutions across a spectrum of industries, meeting diverse needs with efficiency and structural integrity.

Using light steel framing and modular construction has several advantages for thermal performance

• Cost-effective high thermal performance: Lightweight construction enables achieving U-values of less than 0.15 W/m^2K without the need for excessively thick walls. U-values are a measure of the rate of heat transfer through a building element, such as a wall, roof, or window. Lower U-values indicate better thermal performance, as less heat is lost through the element.

• Airtight construction: In terms of airtightness, the construction can achieve levels below 3 m^3/m^2/h, indicating superior airtightness compared to traditional on-site construction. This is crucial, as lower air leakage rates mean less unwanted heat loss, potentially reducing up to 30% of a building's total heat loss. These benefits position light steel framing and modular construction as attractive options for achieving high thermal performance in various building types, including housing, residential buildings, schools, and public sector buildings.

• Predictive Y-values: Extensive thermal analysis leads to predictive Y-values of less than 0.08 W/m^2K in building energy models, indicating superior thermal performance. Y-values are used to quantify the heat loss through building elements such as junctions, corners, and connections. Lower Y-values indicate lower heat loss through thermal bridging, which contributes to improved overall thermal performance of the building envelope.

• Prevention of overheating: High insulation and low thermal mass prevent excessive overheating, ensuring that heat is not stored over successive hot days.
  Responsiveness and reliability: Lightweight systems, being more responsive and reliable due to off-site modular construction, ensure greater reliability of the building fabric.
  

The thermal performance of steel-framed prefabricated buildings depends on various factors, including the design, insulation, construction materials, and the overall building envelope. Here are some key considerations:

• Thermal conductivity of steel: Steel is a good conductor of heat, which means it can conduct and transfer heat relatively easily. This characteristic can influence the overall thermal performance of the building.

• Insulation: The insulation material used in the walls, roof, and floor of the prefabricated building plays a crucial role in controlling heat transfer. Common insulation materials include fibreglass, foam board, mineral wool, or spray foam.

• Building envelope design: The design of the building envelope, including walls, roof, and floor, is critical for thermal performance. Proper sealing, air barriers, and vapour barriers can help prevent heat loss or gain.

• Thermal bridging: Steel has a higher thermal conductivity compared to many insulation materials. This can lead to thermal bridging, where heat bypasses insulation through the steel framing. This issue can be mitigated by using thermal breaks or insulating materials around the steel framing members.

• Energy efficiency standards: Many regions have energy efficiency standards and codes that dictate the minimum requirements for thermal performance in buildings. Compliance with these standards is essential for ensuring energy-efficient construction.

• Cool roof and reflective coatings: For the roof, using cool roofing materials or reflective coatings can help reduce solar heat absorption, thereby improving the building's overall thermal performance.

• Climate considerations: The local climate plays a significant role in determining the appropriate level of insulation and other thermal design considerations. Cold climates may require more emphasis on preventing heat loss, while hot climates may focus on reducing heat gain.

• Ventilation and HVAC systems: Properly designed and efficient ventilation and HVAC (heating, ventilation, and air conditioning) systems can contribute to maintaining a comfortable indoor environment with minimal energy consumption.

• Thermal mass: The thermal mass of the building materials, including steel, can influence how the building retains and releases heat. Utilising materials with high thermal mass can help stabilise indoor temperatures.

• Energy modelling: Energy modelling and simulations can be employed to assess the thermal performance of the building under different conditions. This can help optimise the design for energy efficiency.