The increasing campaign towards green buildings due to concerns over global warming and limited natural resources has made architects and engineers think in terms of sustainability when designing buildings. The following guidelines can be used for the design of high performing envelopes and lighting systems for buildings.

Envelope Design Strategies

The building envelope is the most important element to think of when designing green buildings. A great envelope design will prevent the heating and cooling equipment from working hard and therefore greatly reduce energy consumption.

Windows are the most important element in a building envelope. Double pane windows with low solar heat gain coefficients will provide your building with the proper insulation and solar heat rejection required to keep the outdoor environment from altering the building’s interior conditions. Additionally, overhangs over windows that are facing south and west will block the afternoon solar heat from entering the building. If the building is in cold climate, overhangs should not be placed over windows that are facing east. The morning sun is needed to provide free heat for the building. Windows with low-e coatings also provide an additional layer of insulation to windows.

Use roof insulation with a resistance value of R-13 or greater. Paint roof surfaces with white or light colors or make the top lawyer polished aluminum or tin to reflect heat from solar radiation. Use skylights over atriums, warehouses and hallways to take advantage of natural sunlight.

Finish the top layer of the roof with a heat reflecting surface or paint. The heat reflecting properties of the top layer on the roof is one of the most important factors for rejecting solar heat.The amount of insulation used becomes irrelevant if the roof itself cannot prevent heat from entering the building.

The following table specifies the solar radiation reflective index of the exterior surface of a roof. The higher the number, the better the roof is at rejecting solar heat.

Lighting Design Strategies

Use fluorescent lamps and LED lights and design the building to have a lower lighting power density (LPD) than the one specified in ASHRAE Standard 90.1. Use occupancy sensors in conference rooms, kitchens, bathrooms, store rooms and any other rooms that are not regularly occupied all day. Daylight sensors should be used for lights in perimeter areas. Design buildings to have no corner offices to take further advantage of the sun’s natural lights.

Dim the lights for the entire building by 10%. It is an automatic 10% in energy savings that will not be noticed. The human eye cannot tell the difference, but your electricity costs will be lower. Use a building management system (BMS) and have the building lighting system connected to it to control building luminance levels for different zones. For example, you may want to automatically turn off all your lights at certain time in one side of the building and leave the lights on the other side of the building on. A BMS allows a user to dim lights to create certain ambiances or to save energy if there is enough natural light in a zone.

These building envelope and lighting guidelines will contribute to the design of a very energy efficient building. Lighting can account for 25% of the building’s energy use and a good envelope design will significantly reduce your heating and cooling energy.

The benefits of energy efficient buildings are several: they have lower energy costs, provide tax deductions for the building owner, reduce dependence on fossil fuels, indirectly reduce the creation of greenhouse gases, and increase the property value by making the building more attractive to prospective tenants.

Mauro Small writes for Go Green Academy (http://www.gogreenacademy.com/), an information website on topics related to green living, climate change and sustainability.