IBD Process

The concept of Integrated Building Design (IBD) is based on minimization of all building loads followed by meeting the remaining loads with the best design practices and HVAC equipment.[1] This design approach is illustrated conceptually in the flowchart presented below, which shows four major steps with specific design features included at each step. The following sections provide a more detailed description of each step.

 

Load Minimization: This step focuses on reducing all building loads starting with heating and cooling loads using architectural design features such as building shape and orientation, maximum levels of insulation, high performance glazing systems, optimum window to wall ratios (WWR), optimum SHGC or SC levels and shading strategies. Lighting loads are similarly reduced via good lighting design principles (i.e., selecting appropriate illuminance levels) and use of highest efficacy lighting systems with the goal to minimize the connected lighting power densities (LPDs). The reduction in cooling loads and lighting loads will in turn reduce design air flows. Together with good ductwork design principles (low velocity designs to minimize internal and external static pressure drops) the lower air flows will translate into smaller air handling equipment and fans. Similarly, the reduction in heating and cooling loads will help reduce chilled and hot water design flows and pump sizes. This load minimization is illustrated via a step-by-step application of design features in the “Architectural Elements & Building Envelope” page, the “Lighting & Daylighting” page and the “HVAC Equipment” page.

 

 

It is a vital requirement that all design features mentioned above be introduced simultaneously in order to achieve true low energy designs as the “bundling” of multiple features has the effect of magnifying the potential benefits and the overall financial attractiveness of a project compared to “Value Engineering”, which evaluates each feature in isolation. Typically, “Value Engineering” analysis shows a large number of features such as triple pane windows not being cost effective. On the other hand the bundling of features achieves significantly better returns on investment and in some cases, contributes to an overall lower project cost thanks to the concept of “Tunneling-Through-the-Cost-Barrier” described by Amory Lovins almost 15 years ago. [2] [3]. He reiterated this concept in a 2005 Scientific American article [4] by stating that:

 

“Large efficiency improvements can be cheaper than smaller ones by optimizing the whole building for multiple benefits.

For instance, most engineers would stop add­ing insulation when the expense of putting in more material rises above

the savings over time from lower heating bills. But,  this comparison omits the capital cost of the heating systemthe

furnace, pipes, pumps, fans and so onwhich may not be necessary at all if the insulation is good enough.”

 

The “Architectural Elements & Building Envelope” page illustrates this concept by showing that the combined application of a high performance envelope and reduced WWR achieves larger energy savings compared to standalone technologies, as well as, very large reductions in equipment size.

 

The steps to achieve this extreme load minimization need to be started at the earliest design stages of a project through definition of aggressive design specifications such as target thermal performance levels, amount of window area and lighting loads, to name a few. Preliminary values of all these design specifications need to be selected relative to the prescriptive levels of a baseline or reference building. It is essential that these initial target specifications not be ignored even when an efficient building is to be designed using a “Performance Path” that allows design trade-offs. Setting initial design specifications is especially important for low energy building designs to avoid the creation of flawed designs that would be at odds with the energy efficiency targets. This is a frequent problem in a large number of “green” building projects. The ASHRAE Advanced Energy Design Guides (AEDG) series of publications are an example of design guides that provide prescriptive target levels to achieve 30% and 50% energy savings relative to ASHRAE 90.1 via the use of prescriptive tables that are differentiated by climate zone and building type. [5] [6] This need to define the design specifications as early as possible, well in advance of the schematic design was recognized even back in 1979 in the Energy Conservation Design Resource Handbook of the Royal Architectural Institute of Canada which provides the following statement [7]:

 

The criteria for the building shape, orientation, amount of window area, type of glazing shading devices and other should be developed

simultaneously, right at the design stage with due concern towards the type of HVAC equipment required to minimize energy use.

 

Preliminary energy modeling is normally performed in this step using the initial design specifications to determine the energy performance of the initial design concept. Just as equally important, load calculations need to be performed in parallel, by the design team, particularly for design features that may achieve modest reductions in energy use, but significant reduction in equipment size. The load calculations should be done using appropriate input values that reflect the actual design. These input values would normally include the correct thermal performance of the wall (i.e, "effective Uvalue"), the roof and glazing systems, based on the actual design plus correct lighting loads, plug loads and occupant densities rather than use of default values or guidelines.

 

Size & Select Best-in-Class Equipment: This step builds on the load minimization design work completed in the previous step and can only be done with the willingness of the M&E designer to properly size the equipment using the calculated loads.. The equipment is then sized as close as possible to the calculated design loads avoiding excessive safety margins to prevent operation at low part loads and poor seasonal efficiencies.

 

Heating and cooling equipment with the highest available efficiency is selected together with air handling equipment that is specified with low face velocity coils in order to reduce pressure drops and fan sizes (decided at the earliest design stage meetings, well in advance of the schematic design via a request for sufficient space in mechanical rooms and ceiling). This need for consideration of the physical space for the mechanical equipment is also reiterated in the Energy Conservation Design Resource Handbook of the RAIC with the following statement: [8]

 

The space requirements for the mechanical equipment and distribution system must

be considered before the schematic designs are completed by the architects”

 

Optimized Operation of Equipment: Optimum control strategies are specified including reset control loops for chilled water, condenser water, hot water, supply air temperatures and ductwork pressurization (in VAV systems). In addition, optimal start stop strategies and strict operating schedules are defined to ensure that equipment only operates when needed. Finally, space temperature setpoints are specified for occupied and unoccupied periods and adjusted for different seasons. 

 

Building Commissioning: Building Commissioning is built into the overall design by including a “Building Commissioning Agent” that is responsible for undertaking a thorough “Shake-Down” of the HVAC and electrical systems.

 


[1] This concept was original discussed by Amory Lovins in the 1990s. Additional description can be found in the 1996 ASHRAE article and the 1998 EEBA Conference paper located in the "References" page.

 

[2] Lovins, A., et all. 1999. Chapter 6 – Tunneling through the Cost Barrier. Rocky Mountain Institute. Accessed at: http://www.rmi.org/Knowledge-Center/Library/NC99-06_TunnelingThroughCostBarrier

 

[3] Further discussion of incremental costs and how low energy designs can have much lower costs compared to less efficient designs can be found in the 2006 EIC Conference Paper located in the "References" page.

[4] Lovins, Amory. “More Profit with Less Carbon “. Scientific American, September 2005.

 

[5] ASHRAE Advanced Energy Design Guide Series Achieving 30% Energy Savings Toward a Net Zero Energy Building. There are six guides that cover small office, small retail, K-12 schools, small hospitals, lodging and warehouse/self storage buildings. They can be accessed at: http://www.ashrae.org/standards-research--technology/advanced-energy-design-guides

 

[6] ASHRAE Advanced Energy Design Guide Series Achieving 50% Energy Savings Toward a Net Zero Energy Building. There are four guides that cover small & medium office, medium and big box retail, K-12 schools and large hospitals. They can be accessed at:

http://www.ashrae.org/standards-research--technology/advanced-energy-design-guides

 

[7] Energy Conservation Design Resource Handbook, Royal Architectural Institute of Canada. 1979. Ottawa, Ontario: Section 3.1.7.2

 

[8] Energy Conservation Design Resource Handbook, Royal Architectural Institute of Canada. 1979. Ottawa, Ontario: Section 3.1.7.2


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