Energy modeling, whether completed during design or post occupancy, can deliver a realistic snapshot of energy consumption in your property. GHT encourages developers and tenants alike to invest in energy modeling during the design phase. When utilized properly, the energy model can serve as a powerful tool, allowing the team to make better informed decisions relating to systems selection, operations, and the best use of your project funds.
When built properly, a comprehensive energy model lets you predict how different materials, equipment, or other design and operational decisions will impact energy consumption. Naturally, one of the single biggest factors which determines energy usage is the building’s function, or purpose.
To illustrate the contrasts, simply take a look at these charts from the averaged results of GHT’s recently completed energy models for commercial office and multi-family residential buildings. For the office building, even with assuming a 50-hour work week, the actual “occupied hour” time frame represents only one-third of the year, in terms of total hours.
With the commercial office building only occupied one-third of its total calendar year hours, power and lighting are the primary contributors to the property’s energy usage. Consumption is also impacted by ample amounts of “vampire” power and lighting loads after-hours and over weekends, where the building adapts unoccupied temperature set points. Overall, power and lighting each contribute roughly one-third of the property’s total energy consumption.
Alternatively, residential buildings typically maintain temperature set points of 70-75 degrees Fahrenheit year-round, while actual power consumption from plug loads and lighting remains relatively low. In this situation, power AND lighting represent only one-third of total energy usage, while heating, cooling, ventilation fans and domestic hot water account for nearly 60% of annual energy consumption.
In both instances, an energy model can help developers and property managers understand the expected energy consumption profile for their project, while also identifying areas to get the most bang for your buck.
During the design phase and VE (Value Engineering) efforts, an energy model can help make informed cost decisions. Below are just a few energy saving ideas which present a tradeoff scenario: while initial project costs increase, the property enjoys a significant reduction in operational expenditures over the building’s lifetime.
Suggested strategies to decrease overall energy consumption costs in your new building include:
- Electing R-19 wall insulation, in lieu of R-13.
- Adding automatic sensor control of receptacles to reduce energy lost through vampire power.
- Equipment that captures waste heat from other building processes for use for domestic hot water heating.
- Occupancy/vacancy sensors to control lighting.
As illustrated above, having an accurate energy model can inform decisions to drive return on investment. It can also help protect from value engineering decisions that may save money today at the expense of the future costs.
As Section Head of GHT’s Sustainable Programs studio, James Hansen, PE, BEMP, LEED AP, leads the firm’s efforts to provide services that support sustainable design and has more than a decade of experience developing energy models for commercial, institutional and residential buildings.