Energy Studies

There are certain fundamental tasks that are common to conducting Energy Studies, Re-Commissioning or Retro-Commissioning of an existing building’s systems. Click on Continuous Optimization to view thes tasks.

  • Energy Studies can be “light”, “medium” or “heavy” in terms of content. The costs of the studies are proportional to the effort expended.
  • All energy audits should involve the gathering and analysis of three years of monthly utility bills for electricity, gas and water. Bill data is input into Energy Accounting software employing linear regression algorithms to quantify weather sensitive and non-weather sensitive electricity and gas use.
  • A Building Energy Performance Index (BEPI) is calculated defining the energy use intensity per square foot or per square meter for the building. Comparison of the BEPI to a database of typical buildings enables the Energy Engineer to determine the energy and cost savings potential compared to other buildings of similar type. It does not matter where the building is located because the BEPI can be normalized for the difference in heating and cooling degree days (HDD and CDD).
  • Heating and cooling degree days are quantitative indices designed to reflect how cold and how warm the weather is for a given day compared to a base reference. Each degree of average outside temperature below the base is one heating degree day (HDD) and each degree above the base is one cooling degree day (CDD). The base reference is 18.3°C for residences and can be lower for commercial and institutional buildings where the internal heat gains are higher than those in residences.
  • The base reference is assumed to be the building balance temperature, the temperature at which internal heat gains offset heat losses for heating degree days and the temperature above which mechanical cooling is required to maintain space temperature conditions.
  • The annual energy cost savings multiplied by an acceptable simple payback period in years determines the rough construction cost budget available to implement the Energy Conservation Measures (ECMs).

Walk-through Audit

  • A simple walk-through audit involves a visit to the site. A tour of the site is usually conducted by the Building Operator. The objective of the walk-through is to visit the mechanical rooms, chiller and boiler plant and to get a “feel” for the systems serving the building.
  • If possible, a set of mechanical and electrical drawings is borrowed and taken off site for review back in the office. A shopping list of potential ECMs is developed along with a range of construction costs, corresponding annual energy cost savings and simple payback period in years.
  • A short report is prepared summarizing the findings and recommendations quantifying the energy retrofit and water conservation opportunity. If significant energy savings potential exists a fixed fee is presented to conduct a detailed energy study.

Detailed Energy Study

  • Conducting a detailed energy study is best undertaken by an Energy Engineer who has an in-depth understanding of HVAC design, Direct Digital Control (DDC) system design, coupled with extensive "field smarts" and "hands-on" familiarity with the operation of DDC systems.
  • There are in excess of 40 types of HVAC system hybrids. Familiarity with all types of HVAC systems arms the Energy Engineer with the ability to diagnose whether a system is performing properly or not, and if not, enables the Energy Engineer to determine why not?
  • A fundamental understanding of heating and cooling load calculation techniques, air system distribution design, hydronics system design, pumping system design, and boiler and chiller plant design, enables the Energy Engineer to assess how the building is performing.
  • The need to maintain positive, negative and neutral pressurization relationships as required between adjacent spaces is crucial in the development of effective ECMs. The implementation of variable airflow and variable flow pumping can be very effective in capturing huge energy savings when properly applied. Spaces do not normally need 100% airflow and water flow 24/7. Electrical energy is saved as the cube of the ratio of flow at a given time to design flow rates for air and water.
  • Maintaining proper air change rates and employing effective air distribution is essential for occupant comfort and improved indoor air quality. The goal is to move as much air and water as needed to balance all of the above mentioned criteria in real time.
  • Most but not all existing buildings have had some kind of DDC system installed over the past 29 years. Having the ability to interact with any existing DDC system to analyze current system operation is essental to conducting an effective energy study. Many buildings have had numerous energy studies conducted some of whcih that have been implemented and many which have not and gather dust to this day.
  • The "low hanging fruit" has been "harvested" in many buildings that still have tremendous potential for cost-effective energy retrofit. It takes a savy Energy Engineer to identify this potential, quantify the opportunity and develop a detailed plan for ECM implementation.
  • Being "cross-pollinated" with both mechanical and electrical engineering knowledge and background enables an Energy Engineer to identify and implement synergistic ECMs.
  • The Energy Engineer should have extensive retrofit design experience and construction cost estimating skills. Being able to place oneself in the mind of a contractor and envisage how the ECM can be built results in buildable ECMs and realistic construction costs.
  • Knowledge of various energy savings calculation methodologies from simplistic to very complex are essential tools for the Energy Engineer. The tool chosen for energy savings calculations is all about risk mitigaion. Greater risk management translates into a more rigorous calculation methodology.

  • There are three basic types of manual calculation method.

  1. The simplest is the Degree Day method. It employs a formula that utilizes annual heating degree days for estimation of heating energy savings and cooling degree days for cooling energy savings.
  2. The Temperature Bin method uses discrete 5°F bins of outdoor air temperature in the calculations of heating energy and cooling savings. Each bin has a separate calculation for savings specific to that bin temperature. The annual savings is the summation of all of the individual calculations for all of the outdoor air bin temperatures.
  3. The most accurate manual calculation approach is the Hourly Temperature spreadsheet calculation method. A spreadsheet is created that has 8,760 rows of hourly weather data for a given location. Equations and if, then, else logic are built into the the calculation cells for each type of ECM being evaluated. The sum of the rows provides the annual energy savings for the ECM.

The detailed energy study report serves as planning tool for the budgetary process. The report should have an executive summary, a description of the building and its envelope, a detailed description of the various HVAC system types and the area served by each, a description of the electrical distribution and lighting systems, general observations, a description of mechanical ECMs, a description of lighting ECMs, a description of water conservation ECMs, summary tables for constructionl costs including engineering design, energy and cost savings for electricity, electrical demand, gas and water, simple payback calculations, Net Present Value (NPV) calculations, Internal Rate of Return (IRR) calculations, and Green House Gas (GHG) Reduction calculations for each measure. Synergism between ECMs should be accounted for to eliminate double accounting of energy savings calculations. Example: Reducing the connected lighting load, saves electrical energy for lighting and mechanical cooling but increases the cost of heating energy.

HVAC ECM measures should have developed control sequences described in detail. It should be a short step to get from the energy study report to retrofit design documentation.

The Appendix should be comprised of reduced floor plans colour coded to show areas served by each HVAC system, equipment summaries for fans and pumps, lighting inventory and savings calculation spreadsheet, HVAC ECM savings calculation documentation, ECM construction cost estimates and occupancy schedules.

When the Hourly Temperature spreadsheet calculation method cannot accurately account for the synergism between ECMS, Computer Modeling should be employed. The approach taken is a function of risk managment. The development of an accurate computer model of a building's architectural, electrical and mechanical energy consuming systems mitigates risk. Click on the Computer Modeling tab in the Services menu for a description of computer modeling for new and existing buildings.