Energy Modeling of Buildings (alpha)
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General Information
Description:
Energy modeling of buildings is a practice of evaluating the energy use of a building through simulating and accounting for the many energy related components.
Purpose:
The goal of energy modeling of buildings is to accurately predict the energy use of a building to either test the energy performance of the building with regards to an established standard, or to compare and contrast two buildings in order to find the resulting energy savings.
Industries Served:
All buildings that have significant utility or energy use benefit from energy modeling. Not all energy efficient equipment or practices fit all situations. Analysis through energy calculations are a useful way to predict savings and calculate payback. Care should be taken to find the most worthwhile savings created in exchange for the typically higher up-front cost and effort.
Role of Federal, State, or Governing Authority
Often, building managers or new construction design teams are encouraged to install energy efficient equipment or implement energy saving strategies. Encouragement comes in the form of potential for future energy savings, an abstract point system (LEED, Green Building Standard), region-wide mandates (e.g. NYS Executive Order 111), or financial incentives. If by definition, an energy efficiency or Energy Conservation Measure (EEM/ECM) generate savings, in many cases this savings do not justify the (unreasonably) high up front cost. Incentives help to offset the high initial cost of equipment and to reduce the number of years that it will take for energy savings to break even with initial costs.
Incentive websites:
- DSIRE's Database of State Incentives for Renewable Energy and Efficiency
- NEW YORK STATE ENERGY and RESEARCH DEVELOPMENT AUTHORITY NYSERDA Funding list and list of current list of PONs (Payment Opportunity Notice)
Problems with Energy Modeling of Buildings
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Diversity of Modeling Programs and file formats are not coordinated among the trades.
- Possible solution: Common File formats (programmer's are addressing this issue slowly)
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Software revisions occurring faster than users understanding of a program's capabilities.
- Possible solution: Users signing up to receive notifications from software makers about new capabilities. Users diligently reading program documentation when available. Budgets for projects allocating time for continuous training, and learning.
- Software revisions occurring slower than advances in new building technologies.
- Possible solution: An industry forum with user evaluation of programs, a toolbox of justifiable techniques of to supplement and support a program's lack of capability.
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Incomplete qualities or disadvantages of programs are sometimes hidden or difficult to evaluate.
- Possible solution: An industry forum with user evaluation of programs.
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Unknown, Energy Data. This arises from multiple reasons: Region or market wide energy studies are often too broad and over generalize, manufactures of energy efficient equipment have an inherent conflict of interest, the energy efficiency websites have a target audience of consumers and not energy modeling professionals, design engineers size equipment to peak demand and seldom consider yearly energy use, and conflicting information is abundant even among modeling advise sources. These problems also pertain to links and information presented on this page.
Methods
Classification of the different methods are diverse in their practice but generally subscribe to the goal of predicting energy use. The choice between the different methods is primarily based on level of accuracy desired and what methods, codes, or standards a governing body requires the modeler to adhere to.
- Computational Fluid Dynamic (CFD) simulations
- Hourly/Sub-Hourly simulations (eQuest) -A detailed summary of each hour of the year and the hour-by-hour energy operation of the building.
- Comparative Summary Tools -Use a database to rate the building's energy efficiency in regard to other buildings.
- Custom Measure tools. -Non-Interactive method of looking at one measure at a time.
Existing Building Simulating Guidelines
-with a brief review of useful content
- NYSERDA Multifamily Building Performance Program Guidebook
- What it has:
- Nearly all Residential modeling information: Dhw, Room temps, Ach, plug loads, Dorm vs. Apartment building adjustments, schedules, etc.
- A very comprehensive analysis of available technical information and other guides on common building modeling practices and techniques for residential buildings.
- What it lacks:
- It is not ASHRAE 90.1 2004 APPENDIX G
- Anything commercial, retail, or industrial in nature.
- LEED NC 2.2
- What it has:
- Different methods of calculating energy use in buildings
- Charts of typical building energy use, along with some occasionally useful assumptions.
- Charts of shower flow rates
- References to ASHRAE 90.1 2004 Appendix G.
- Many great references to energy efficiency efforts, rules, and standards around the country and the world.
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- What it lacks:
- ASHRAE 90.1 2004 Appendix G.
- What it has:
- Lighting loads, nearly all baseline information, detailed descriptions of modeling techniques with respect to what can and what cannot be in the models.
- HVAC efficiencies of baseline (from references to ASHRAE 90.1 2004 main document)
- Wall construction assembly U values, etc. (from references to ASHRAE 90.1 2004 main document)
- Zone definitions, what makes up a segmented thermal zone.
- Heating Degree Day values for most regions, including Design Day temperatures. (from references to ASHRAE 90.1 2004 main document)
- Adenda and revisions that better focus the scope of the document (see below for down side of this)
- What it lacks: (Technically, it lacks nothing, but covers all undefined modeling assumptions with broad statements that vaguely fill in the blanks when questions arise.)
- Schedules, or guidance in scheduling of occupancy, hvac, special equipment.
- Air change and exhaust specifications
- Dhw values
- Clear definitions of accuracy of modeling besides: "Less than 300 hours of load not met for entire building" -regardless of sf of building.
- Electric plug values.
- Easy application to situations where measure complexity exceeds the modeling capability of the software modeling program.
- A clear explanation for the reason behind wrap around windows in the baseline model.
- Easy application to Commercial, Residential hybrid buildings.
- Any general guidance on facilities where the magnitude of energy use is extreme, such as with Data Centers, IT rooms, etc.
- Adenda and revisions that all energy incentive authorities accept.
- NREL 2005 California Nonresidential ACM Approval Manual
- What it has
- Receptacle loads for typical spaces
- General modeling information to conform to California's modeling practices
- Schedules and thermostat settings.
- Thermostat setback control schedules
- Schedules for Equipment, occupancy for residential and non-residential
- What it lacks it
- Overlaps other Modeling Standards such as ASHRAE 90.1 2004 APPENDIX G
- Before using the people/sf values read the fine print about double occupancy factor within the data.
- Simulation Resource Group -A very good resource,
Software
Review and summaries of different software package capabilities.
- Contrasting the Capabilities of Building Energy Performance Simulation Programs written by Department of Energy in 2005. The information is old but the document is a very substantial review of programs, what they do, what they can't do, what they take into account and what physical phenomena is simulated directly or merely estimated.
- DOE's Building Energy Software Tools Directory. -This chart evaluates existing tools among two criteria: 'Free' and 'Recently Updated'. Additional evaluation is listed upon clicking on each program:
- Key words, Validation/testing, Expertise Required, Users, Audience, Input, Output, Computer Platform, Programming Language, Strengths, Weaknesses, Contact, Purchase
- IBPSA New York Chapter's review of simulation programs.
Software Programs
Modeling Resources
- A few words on the different types of numbers specific to energy modeling.
- The Up and Down chart of modeling
- Integration of the energy modeling process into the construction process
- Maps Maps Maps
- Units, Conversions, and Definitions common to Energy Modeling:
- Cooling (ton, vs. hp, Btu, vs. mBtu, vs. mmbtu, vs. kw)
- Heating (mmbtu, Mbtu, mmbtu/h, Mbtuh....)
- Gas (cf vs btu)
- Electricity and Motors (Var vs. kWh, vs. 3phase current vs. 2 phase current, vs 490volt ac vs. 280 volt vs. 110 volt vs. kW vs btu, with Horsepower calculation)
- General Conversions web site
- HVAC units, types, terms, setup,
- SEER vs, EER, vs COP, vs Efficiency, vs BTU/BTU.
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- Utility Bill Interpretation, Information
- New York Region
- United States Utility Information per state with news about Utilities
- California Utility
- Oregon Utility
- Codes
- Typical water use of Buildings
- Tap water and Sewage use of buildings from American Water Works Association (needs new link)
- See also LEED NC 2.2 book for many references and a standard to calculate typical and baseline water use.
- Typical Energy Use of Common Buildings
- Charts from EERE's Building Energy Data Book Relevant to Energy Modeling of Buildings. Warning: Some heating and cooling data is from averaged US Buildings over different climates.
- Typical Commercial and Retail buildings
- Typical Energy use per building type
- Typical Hospital lighting, equipment, wall construction.
- Typical Domestic Household Energy Use, Construction, Equipment, Expenditure by region
- Typical Commercial HVAC thermal distribution energy use per building type
- Typical HVAC efficiencies
- Typical Insulation Material R values
- Typical Lighting: lights per bldg, lumens per watt, watts per bulb, bulb lifespan, hours use per day.
- Typical Office loads, gains, and typical construction
- Typical On-Site generation CHP, PV Installed Cost per system size
- Typical School construction and energy use
- Typical Window U value and SHGC
- Typical heating factors for common buildings -no case study, or scientific data, just experience
- eia Energy Information Administration consumption of Residential buildings -large quantity of data most is a sum of an entire sector of the energy market but there are some w/sf values.
- eia Trend analysis
- eia Energy outlook and predictions of consumption -large quantity of data where most information is a sum of energy used over entire sector of market
- LEED baseline, improved vs. actual building utility use. -A very informative report covering important topics. Note: Baselines are ASHRAE 90.1 1999 NOT ASHRAE 90.1 2004!
- Shows reduced energy savings potential among cold climates
- Shows wide standard deviation of modeled vs. actual utility bills.
- Typical Energy Use within and about Specialty Buildings
- Cost Estimation -Cost estimation is more of an art than a science.
- Acronyms Common to the Energy Industry
- MEGA SITES -These are vast information resources not particular to energy modeling, but contain very useful information on energy measure application, and expectations of performance, cost, etc. You should be advised that you can spend the greater part of your day navigating their information.
- The Sustainable Condo
- Building Inspection Sites -Building Inspectors often have the role of commisioning agents, fixing problems and sometimes, analyzing savings for upgrades. There are several websites out there describing the field:
- BuildingGreen.com
- Alliance to SAVE ENERGY worldwide listing of energy efficiency organizations
- Toolbase Services -A nice general review of costs, technology, application and case studies for different energy efficient measures.
- Energy Star -Big site of all Commercial Appliances, Specification text, savings calculators.
- DOE Department Of Energy
- Whole Building Design Guide
- EERE Cost calculators for various equipment
- Lighting
- Chillers,
- Boilers
- Food service restaurant equipment
- Office equipment (computers, monitors, etc)
- Residential Air conditioning
- Residential appliances, Dishwashers, clothes washers
BASELINE BUILDING fundamental characteristics
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Fundamental Building Principals, Physics, and Attributes.
- Gains vs Loads
- Gains
- Thermal transfer, Radiative, Conductive, Convective
- solar
- lighting
- equipment
- physiological body heat
- Loads
- System capacity sizing
- System response
- System control
- System per zone vs, multi-room/multi zone systems
- Outside Air
- Air leakage and air leakage calculators
- HVAC exhaust-supply offsets
- Wind effect on Air Infiltration
- Cracks in building envelopes
- Stack effect through all Elevator, mechanical shafts, and stairwells.
- Air buoyancy effect through all elevator, mechanical shafts, and stairwells.
- Exhaust
- Affect exhaust fans have on building infiltration
- Typical rooms under exhaust
- Specialty Exhaust rooms
- Parking Garages
- Bathrooms
- Chemical work stations and Laboratories
- Repair Garages
- Fresh Air Supply (Mechanical Ventilation)
- Code required Outside Air per Space use
- Common Outside Air assigned to spaces for additional comfort.
- HVAC
- Duct Pressure Drop Calculation tool
- CVCT systems
- VAV systems
- PTAC systems
- Typical residential systems (urban)
- Typical industrial systems
- ASHRAE SYSTEM TYPES VS EQUEST PROGRAM INPUTS
- Envelope and Building Shell
- Thermal bridging
- Exposed floor slab, balconies
- Roof dynamics
- Cavity wall physics
- Moisture barrier
- Wall construction type dependencies on local climate.
- Industry Websites:
- Occupancy
- Occupancy Schedules:
- Residential
- Health Care facilities
- Commercial
- Office
- Thermostat Schedules
- Residential
- Health Care facilities
- Commercial
- Office
- Lighting Schedules
- Residential
- Health Care facilities
- Commercial
IMPROVED BUILDING characteristics and helpful information
Special notes and approaches on how to implement a energy efficient technology into a building energy model
Edit note: Few links below contain information, this in need of work
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