23 and We…
…Throughout the development of the school project, we have been focused on reaching an energy use target of EUI 23. What does that mean, how do we get there, and are we getting close to our goal?
First, a refresher, what is EUI?
Energy Use Intensity (EUI) = The amount of energy (kBtu) consumed per square foot of a building. It is calculated by dividing the total amount of energy consumed in 1 year by the number of square feet in the building.
Currently, the school’s EUI is about 65. Why are we trying to get to 23? That is how efficient the building should be in order to be net zero “ready.” Then, the solar PV we put on the roof and over the parking lots will offset the electricity use of the school, making it a net zero building. We are on track to be the first net zero school renovation in the state!
How do we drive down electricity use? There are several main components:
- The building envelope: Highly insulated walls and roofs, and energy efficient windows.
- Mechanical systems: All electric heating and cooling with a heat recovery system (see below to dive deeper into VRF and heat recovery systems).
- Lighting: An LED lighting system that can gauge and adjust to the amount of natural light.
- Plug load: How do we use the building? What are our electricity habits? This piece of the puzzle will require all of us who use the building to consciously consider our behaviors.
How are we doing so far? SMMA just ran an energy use model of the building at the Schematic Design phase. As of now, the school has a predicted EUI of 23.39! Energy models will be run again at the end of Design Development and during the Construction Documents phase.
Click here to see the slide deck from the February 13th meeting. It gives an overview of proposed systems and the energy model.
Do we still have your attention?
What is a VRF system? What is a heat recovery system? Whether or not you are an electrical or mechanical engineer, this technology is pretty cool!
For those interested in the punch line, the goal of these systems is to create a consistent and comfortable indoor environment. They take into account outdoor temperature, solar heat load, and humidity, and can balance out different conditions in different parts of the building.
For those who want to know more…
While the details will be worked out over the coming months, the design team team is proposing some very interesting technologies for air quality, building comfort, and minimal energy usage to achieve our net zero goal.
Traditional heating and cooling systems are usually 100% “on” or “off”. For example, your house may clunk and creak when the boiler fires up, or lights may briefly dim when the A/C kicks on. In contrast, the systems for our new building will have “modulated” or “variable” operation: compressors and fans can run at partial capacity. The resulting system is quieter and more efficient, and can balance heating and cooling needs much more effectively (e.g. one classroom is receiving full sun and another is not).
Ventilation is another issue, as modern buildings are extremely well sealed. The design team is proposing “energy recovery ventilators” (ERV), a type of heat exchanger. ERVs efficiently transfer most of the heat from outgoing stale air to incoming fresh air (or the reverse in the summertime).
In addition, rooms will have sensors to detect occupancy via the carbon dioxide (CO2) emitted by people. That information is used to optimize air quality (through ventilation) as well as heating and cooling needs.