2. Designing for Climate 

Adverse temperature conditions can be designed for, depending upon the environment and the use of the building. If heat control is important for the building end use, such as for human comfort or livestock optimisation, then a number of issues should be considered:

2.1 Issues for design in hot climates¹

Careful design can reduce cooling costs, contribute to lower energy costs and more responsible use of resources. Locate the building on the site to take advantage of its natural benefits. Look for shade areas  typical wind directions, and the building's aspect relative to the sun to protect the building from undesirable heating affects. Issues to consider are:

• Building aspect - Position windows away from direct sunlight, and use thermal mass thoughtfully, keeping mass away from the hottest areas of the house like the roof or sunset facing walls. Once these areas get hot, they radiate heat back into the building, prohibiting nightime heat relief.
• Design for shade - Use wide eaves in the direction from which harsh sunlight originates. If possible, protect windows in harsh or direct sunlight with natural shade trees, steel louvers, external blinds or shutters. The best result is achieved by preventing the sun from gaining access to the building.
• Utilise natural convection - Position windows to capture wind currents so that natural convection cools the building. Use thermal chimneys to create heat spots where air naturally flows to create convection currents throughout the building.
• Use colours for their natural impact - Black-coloured roof ridges or black chimneys can provide contrast to buildings but also are a simple way to create convection currents. Black components tend to absorb energy from the sun, heating up and attracting high wind flows. Light colours or natural metallic finishes reflect heat from the building, leaving less to be absorbed.
• Artificial Cooling - Use air conditioners sparingly since they contribute significantly to the building's Life Cycle Analysis (LCA). If we typically look at cradle-to-grave building life (construction, use, reuse and disposal), 85% of the energy is consumed during the use phase. Giving consideration to how the building is used can significantly contribute to reducing energy and carbon usage in the environment.²
• Use modern building materials and practices - double glazing, insulation.

2.2 Issues for design in cold climates³

Similarly careful design can reduce heating costs and take advantage of steel's flexibility in contributing to lower energy consumption and more responsible use of resources. In this case we reverse the issue and look for ways to capture the natural heating from the sun. Issues to consider are

• Building aspect - Position windows toward direct sunlight and use thermal mass thoughtfully, using mass to heat the house at night when the sun goes down.
• Design for sun - Use narrow eaves and try to get windows and thermal mass warmed by the sun.
• Create air tight buildings - Avoid draughts and convection currents by using insulated panels or steel sandwich panels. Design to remove thermal bridging where heat loss can occur through natural conductors like metals, and use insulation sensibly to prevent heat loss from living and working spaces.
• Use colours for their natural impact - In this case, use colours that absorb heat and aid in contributing to the thermal mass of the building.
• Artificial Heating - Again use artificial heating devices sparingly since they contribute significantly to the building's Life Cycle Analysis (LCA). Wise insulation, controlled air tightness and using the sun's natural impacts through thermal mass, double glazing and prevention of heat loss will reduce heating bills.

2.3 Issues for design with static loads

Static loads are the forces that a building must support over a period of time. These loads could occur from the general self-supporting nature of the building, to handle certain crane loads of other application conditions, or to handle adverse weather conditions like snow or heavy rain or water.  Another issue to consider is foot traffic during roof inspections or general maintenance. These conditions can be designed for using steel. Issues to be considered:

• The building foundations and structure need to be able to support the design loads.
• Aesthetic - Is the roof a building feature or is it flat or hidden?
• Rafter spacing needs to be considered. For heavy loads 600mm are common but for lower loads, rafter or purlin spacings can be over 2000mm.
• Roofing material - Composite panel, double steel skin systems, single steel skin systems can be considered.
• Roof sheet profile. By introducing different profiles, the load carrying capacity of the roofing sheet can be substantially increased. Flat surfaces can show foot traffic damage. A slight profile will strengthen the sheet and hide damage. Textured low gloss surfaces will similarly hide damage. High-gloss surfaces will highlight any issues.
• Roof slope.
• Water drainage and catchment systems. Can the roof handle the off flow of water or will the roof create a reservoir where water will collect, increasing the load and possibly contributing to water ingress?
• Expansion and contraction systems to handle winter and summer environments.
• Fastening systems. Nailing, screwing, clips, washers, concealed fixing systems should be considered.

2.4 Issues for design with dynamic loads⁴

Dynamic loads are the forces that a building must support during adverse weather conditions. Cyclones, hurricanes, and tsunamis all fit within these definitions. Steel designs need to allow for the direct pressure of the wind as well as the uplift from differential wind velocity air pressures over the building and the air pressure within the building. Issues to be considered,

• The building structure cyclone rods and cross bracing use should be considered.
• Rafter spacing needs to be considered.
• Roofing material - Composite panel, double steel skin systems, single steel skin systems should be considered.
• Roof sheet profile.
• Roof slope can impact air pressure uplift.
• Expansion and contraction systems to handle winter and summer environments.
• Fastening density. Increased fastener density should be considered.

¹ Refer to local design codes for guidance on design issues in your area.

² Refer LCA studies by BSL, Corus etc

³ Refer to local building codes on thermal design and air tightness design parameters or talk to your local steel supplier.

⁴ Check with your local steel supplier or government authorities for wind loads in your area.

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