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Page history last edited by Brian Matthews 8 years, 10 months ago

Energy Modeling of Buildings (alpha)

Notice to all users:  This page was not kept clean and edited by entrusted personnel, all users will have reading status only.  Original editors from IBPSA will retain editing control.    It is currently undergoing a cleaning from spam so please excuse the mess.  A system of public editorial is under review. 

Welcome to the energy modeling of buildings wiki, initiated by IBPSA-USA-NY (International Building Performance and Simulation Association, the New York Chapter of the United States Affiliate).  We welcome you to edit the content and format of this wiki.  Like any wiki, this site is a work in progress and is only as good as the content posted by members.    Creating an account is as simple as signing up in the top right hand corner of the page.  Thank you for visiting our wiki!

 

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:

 

 

Problems with Energy Modeling of Buildings

 

  • 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)

  • 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.

  • Incomplete qualities or disadvantages of programs are sometimes hidden or difficult to evaluate.  

    • Possible solution:  An industry forum with user evaluation of programs.

  • 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.

    • Possible solution:  The building simulation community gathering information and evaluating it on a wikipedia type forum. 

 

 

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.  
      •  
    • 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.

   Software Programs

 

 

Modeling Resources

 

 

 

BASELINE BUILDING fundamental characteristics

  • 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 
    • 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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