IES Consulting were contracted to assist HGA Architects and Engineers with the LEED Energy Modeling for a new ELAC Campus Language Arts & Humanities Building. This included assessing the energy performance, demonstrating the savings anticipated from the natural ventilation system and investigating ways the building could efficiently utilize the new district energy plant. The project is a five story New Construction (NC) building which has been designed for high energy efficiency by including high performance lighting systems with daylight dimming, a high performance building envelope and active beams with high efficiency ventilation fans for mechanical ventilation when needed.
The first portion of the project was to more accurately model the building performance and corresponding energy savings from the use of operable windows to naturally ventilate the spaces. In these cases, the building operates in a ‘mixed-mode’ configuration where occupants are assumed to open the windows when ambient conditions are conducive to natural conditioning. These unique systems were explicitly model using IESVE ApacheHVAC system modeling tool in conjunction with IES MacroFlo bulk airflow modeling tool.
Each room using a mixed mode strategy includes an LED operable window indicator. This LED indicator assists the occupant(s) on when conditions are favorable for opening windows. A green light indicates a favorable condition to open windows. Conversely, when the red LED is on, windows should be closed.
A green condition is triggered by the following:
- Room air temperature greater than 71°F
- Room CO2 level less than 500 PPM (above ambient CO2)
- Outside air temperature range of 60°F to 70°F
Contact switches on all operable windows indicate whether a window is open or closed. If an occupant opens a window and if the above conditions are confirmed, then VAV box damper will close and the space will be naturally ventilated.
A red condition is triggered by the following:
- Room air temperature less than 70°F or greater than 74°F
- Room CO2 level greater than 500 PPM (above ambient CO2)
- Outside air temperature less than 60°F or greater than 70°F
Upon a red condition the VAV box will adjust the damper position to ensure adequate ventilation is provided in the event that a window remains open and CO2 levels are above the required set point.
The Mixed-mode system controls ensure that all spaces are adequately conditioned and ventilated at all times.
The second challenge for the project was to demonstrate energy and energy cost savings by connecting to the newly constructed central utilities plant. To accomplish this, IES Consultants used IES’s most innovative technology; its VE Masterplanning tools and IES-SCAN technology. To demonstrate LEED savings, the Project followed the USGBC’s District Energy Modeling, Option 2 (full accounting) path. This meant using VE Masterplanning tools to enable consultants to model groups of buildings and run high level simulations to obtain combined annual (8760 hours) load profiles of the buildings. IES-SCAN technologies provide tools to import, interrogate and analyse building performance data which can be imported to VE models to increase simulation model accuracy.
IES Consulting used VE Masterplanning to create and simulate a high level model of the entire East Los Angeles College campus which took into account the individual buildings served by the district plant. The model produced annual heating and cooling load profiles for each of the buildings served by the district plant and aggregated those into an overall heating and overall cooling profile for the campus, over a year.
IES consultants were then able to use IES-SCAN to convert the VE Masterplanning model results into two free form profiles to be used as VE model inputs. This allowed the consultants to then take advantage of IES VE detailed HVAC modelling to accurately simulate the district plant performance over the year. The results of the district plant model led to accurately calculated seasonal COP values for heating and cooling plant which were then applied in the LEED Energy Model.
By doing this, IES Consultants were able to help the team design a high performance building and attain the appropriate LEED energy points. In summary, the project expects to use over thirty-two percent less energy than the baseline case at a cost savings of nearly thirty-one percent or about $90,000 per year.