Prescriptive Approach to Energy Efficiency–a Cost Effective Alternative

Energy efficiency the most important factor defining a High Performance Building. There are two paths to increase a building’s energy efficiency in relation to a “brown building”. You  could use a performance-based approach in which a baseline energy consumption is established and the building is designed to reduce energy consumption below that baseline.

Alternatively, you could use a prescriptive approach to attain compliance under which the building is designed to meet the requirements of an existing prescriptive standard. Typical examples of such standards are ASHRAE 90.1 and the International Energy Conservation Code (IECC).

Although the performance-based approach is the most accurate method to predict quantifiable energy use reduction, the cost associated with this approach can be significantly higher than the prescriptive approach. These costs are related to the energy model that has to be developed by external agencies.

The prescriptive analysis, while it may not predict accurate energy consumption, eliminates the energy modeling step hence lowering cost of implementation. Existing prescriptive standards such as ASHRAE 90.1 are products of excellent research and are constantly updated to meet current standards. By meeting these prescriptive standards, you can be assured of designing a building that is truly energy efficient.

The green building industry has made significant strides in the past decade but still has still some way to go before it becomes a mainstream construction technique. A method to ensure its growth is to reduce excessive third party costs like the aforementioned third party building modeling costs. Hence building codes and green building certifications must have an option for owners to choose between prescriptive and performance-based approaches. ASHRAE 189.1 and SERF are great examples of a building code and certification which provide this option.

Organizations are beginning to understand and embrace the prescriptive approach. For example, the US Army recently decided to upgrade their existing building codes to ASHRAE 189.1. Both ASHRAE 189.1 and SERF help the effort to increase the cost effectiveness of the green building process by adopting a dual approach to building energy performance.