Computer Modeling

Realistic Computer Modeling of building systems can best be described as a blended form of arts and science that enables a modeler to create a "living and breathing" model accurately representing a proposed and/or existing building's architectural, mechanical and electrical energy consuming systems.

An effective modeler must have a broad base of engineering and building energy systems diagnostic skills. An understanding is vital in the use of a number of computer modeling programs including their strengths and weaknesses. Effective input and output interpretation are essential to prevent the “garbage in, garbage out” syndrome. A model generating pretty charts and low energy use does not equate to accuracy in calculating peak heating and cooling loads, and prediction of the building’s energy consumption once it is built or retrofitted.

CES Analytics has this level of expertise with modeling experience spanning 38 years. We are fluent in eQUEST, DOE-2.1E, EE4,  TRACE 700 and IES-VE computer modeling programs in both new construction modeling and existing building modeling.

CES Analytics has extensive background with existing building retrofit design, conducting energy audits, calculating energy savings manually and by spreadsheet, designing and commissioning Direct Digital Control systems, commissioning HVAC systems (hands-on) and testing and balancing air and water systems. These skills enable us to "sanity check” the model built so represents a real world operation.

The simulation model is comprised of four modules; some programs combine systems and equipment into one module.

• Loads
• Systems
• Equipment
• Economics

Loads Module

The Loads module defines the architecture of the building in terms of its surface orientations, elevations, surface areas (windows and doors), materials composition (wall, glazing, roof and floor), thermal zoning (space layouts/areas), wall U-values, wall areas (gross and net), roof U-values, roof areas, glazing U-values, shading coefficients, glazing area, internal shading devices, skylights and overhangs, vertical side fins, floor U-values, floor area, adjacent structures and landscape, gross area and net (conditioned area).

Electrical / Internal Loads:

Lighting power density (by HVAC zone), design luminance (by HVAC zone), peak occupancy (by HVAC zone), and peak equipment (by HVAC zone).

Internal occupant loads are input to simulate number of people and level of activity producing corresponding sensible and latent heat gain into the space.

Systems Module

The Systems module defines the types of HVAC systems proposed for the new building or systems existing in the building to be retrofitted. There are almost forty different types of HVAC systems including hybrids with which a modeler needs to be familiar. Should a modeler not understand the complexities of HVAC system design,and DDC controls systems operation, there will be liitle chance of developing a model that simulates accurate energy use in the real world.

Equipment Module

The Equipment module defines the types of HVAC system equipment to be modeled; i.e. rooftops, air and water-cooled condensing units, air handling units, fans, air and water-cooled chillers, steam, hot water boilers (condensing and non-condensing), cooling towers, fluid coolers, pumps, fan coils, unit heaters, baseboard radiation, full load and part load equipment energy consumption profiles.

Calculating peak loads for heating, cooling, lighting and plugs is the easy part. The energy simulation program calculates hourly loads for 8,760 hours per year. In order to calculate the loads accurately, realistic 24 hour day schedules for Sunday through Monday by month must be developed for occupancy, lighting, and plug loads for each thermal zone. The simulation program prorates the internal loads that enter the space as heat gains to be processed by the HVAC system according to these schedules (0 to 100%). Thermostat settings and schedules for each day must also be specified.

Design parameters must be input for each air handling unit including anticipated coil leaving air temperatures, minimum outside air quantities, fan schedules for each day of the week, and anticipated fan static pressure and efficiency.

If the building has a central plant, inputs for entering and leaving chilled and hot water temperatures, pump heads for chilled water, condenser water and hot water heating systems, and equipment control sequences are required.

Economic Module

Base case first costs for equipment and systems affected by energy conservation measures and ECM construction costs must be input. Applicable and optional utility rate structures for electricity, electrical demand and natural gas (or other fuels) enable the simulation program to calculate the cost of energy use by month and year by energy type. Utility escalation rates and the cost of money can also be input for life cycle costing purposes.

For description of the scope of work and our methodology in providing Computer Modeling services on a typical new construction project or an existing building click on Computer Modeling - New & Existing Buildings hotlink.