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Energy Audit "When you can measure what you are speaking about, and…

- - - - Comparison among similar buildings
      - Individuation of bad Energy Performance and behavior of the building:
        
        Comfort indexes;
        
        Energy indexes #
      - Requirements for a deeper analysis (larger order level of investigation)
    - - Interviews with site-operating personnel
      - Reviews of bills and other operating data
      - Walk-through of the facility to become familiar with the building operation and to indentify any possible sink of energy
        
        Implementation cost of possible intervention, SPBT and general calculation to assess improvements
      - Establishment of the steps and the areas of concern to be improved
    - - More detailed informations are collected to allow the Auditor to assess facility's energy demand and Energy usage profiles
      - Deeper level of analysis with on-ste measurements and computer based simulation tools to have an optimal description of the scenario
    - - Both energy and non-energy investments are rated on a single set of financial criteria that generally stress the expected Return On Investment (ROI) or Net Present Value (NPV)
      - Projects must be developed such that they provide a high level of confidence -> guaranteed savings
  - - - Practical factors may encourage some ECOs rather than others
      - Energy and economy factors have to be seen together in order to find, for each retrofit action, the cost of energy saving
    - - Usage of a simulation model of the building
        
        1. Transmission losses
        
        2. Ventilation losses
        
        3. Internal gains
        
        4. Solar gains
        
        0. Identify system boundaries and Outdoor climate quantities
      - Each ECO should be ranked according to the cost of energy savings (Example: the ECO who lead to a larger energy saving should be performed ASAP)
      - After the retrofitting intervention, the building has to be monitored to assess and to evaluate the differences between the expectations and reality (PIPA)
        
        N.B. each family behaves differently, so it may happen that expectations are different from reality
- - - - Blower door testing is made with a specially calibrated device to assess the air leakage of a room or a building, by depressurizing it with a fan and finding cold spots from which air goes outside (according to UNI EN 13829 Standard)
    - - Air change rate
        
        Decay method (q=0)
        
        The tracer gas (SF6, N2O, …) is injected in the environment and mixed by a fan. Once the concentration reaches the desired level tracer gas injection is ceased and one should wait until concentration stabilizes.
        
        Tracer gas methods measure air infiltration rates over a short period of time
        
        Step-up method (q=cost)
        
        Constant concentration (C=cost)
        
        Perfluorocarbon Tracer Gas (PFT) method
        
        The PFT technique uses two pencil-size devices. One, the emitter, gives off a small amount of a colourless, odourless, and harmless perfluorocarbon (PFC) gas. The other, the receiver (made with a carbon molecular sieve* cartridge), absorbs some of that vapour from the room.
        
        At the end of the test period, the receiver is recapped and sent, along with the temperature readings and room volumes, to the Tracer Technology Center at BNL for analysis, where an expert must analyze the results. The TTC sends the customer a computerized test report that includes the average air infiltration rate
      - Air distribution indicators
        
        "Age of air" concept
        
        For a ventilation system consisting of one inlet and one outlet duct is equal to the inverse of ACH 1/n
        tau_e=tau_n nominal time constant
        
        Pulsed injection
        
        Concentration growth
        
        Concentration dacay
        
        Global air change index
        given from the ratio between nominal time constant and the average age of air
        
        Air change efficiency
        
        Nominal time constant of contaminant
        
        Hood capture efficiency
  - - - A thermopile, a certain # of thermocouples connected in series to amplify the signal, measures the diifferential temperature across the sensor, that is proportional to the heat flux