EnergyPlus

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  1. ASTM C1340 convection algorithm for attic spaces

    The calculation of convection coefficients on the surfaces for spaces representing attics in EnergyPlus has been shown to have inaccuracies when compared to empirical data and building models that specialize in attics. The ASTM C1340 standard has a set of correlations for these convection coefficients that has been empirically validated. An EMS approach to implementing these convection coefficients is available, but it would be much more usable to have it incorporated as a new object in EnergyPlus.

    3 votes
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    0 comments  ·  Envelope  ·  Admin →
  2. Model the evaporative cooling process of building envelope after rain events

    The evaporative cooling process of walls and roofs after rain events can have significant impacts on building envelope performance, especially in hot-humid climates. This cooling process cannot be modeled with EnergyPlus.

    1 vote
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    1 comment  ·  Envelope  ·  Admin →
  3. Integrate Window Calculation Engine

    EnergyPlus currently has three different calculation modules for the detailed calculation of thermal, solar and daylighting properties for fenestration systems:
    1. Original window module implementation (referred as "Winkelmann" here)
    2. Tarcog/BSDF
    3. ASHWAT/EquivalentLayer

    Calculation modules a) Winkelmann and b) Tarcog/BSDF use the same calculation standard (ISO 15099) and for specular systems, they produce very similar results (for surface temperatures and heat flows). The Winkelmann calculation modules include optical calculations for both specular and lambertian, grey body diffuse reflectance of venetian blind slats and woven shade threads. The Tarcog/BSDF calculation module, on the other hand, lacks optical calculations in EnergyPlus and…

    12 votes
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    in progress  ·  3 comments  ·  Envelope  ·  Admin →
  4. Report Whole Window U-factor, SHGC, and VT

    Problem: EnergyPlus only reports U-factor, SHGC, and VT for center-of-glass. It does not report those values for the whole window.

    Rationale: It is very important for modelers to confirm that the window systems (glass layers, gas layers, frames, dividers, shades, etc.) have been input correctly and reporting standard rating values from EnergyPlus’s models is very helpful to close the loop.

    Solution: Add content to the fenestration summary report for whole window U/SHGC/VT. Calculate the whole-window metrics using procedures defined by NFRC and consistent with LBNL Window program. Correct any problems with how frame and edge-of-glass regions are input and modeled…

    24 votes
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    2 comments  ·  Envelope  ·  Admin →
  5. Issues on operable windows when they are open

    Currently EnergyPlus considers airflow change (various approaches) through a window when it is open. However, no changes are considered for: heat transfer (convection to room), solar heat gains through the window to the room, solar shading on the façade, long-wave radiant exchange between the window surface and other interior surfaces of the room. This leads to errors in modeling natural ventilated buildings, e.g., low-e windows still take credit of lower solar heat gains when windows are open.

    5 votes
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    1 comment  ·  Envelope  ·  Admin →
  6. Add Thermal Mass and Resistance to Naturally Ventilated Exterior Cavity

    Problem: The model currently assumes the exterior cavity is bound by a thin baffle with the same temperature on both faces.

    Rationale: Research has shown significant energy conservation potential associated with massive baffles, such as concrete roof tiles installed over a baffled air space over the roof decking or EIFS systems with insulation exterior to a ventilated gap.

    Solution: Expand the exterior ventilated cavity module to include massive and insulative baffles. Benchmark the new code using available experimental and analytical data.

    Context: The model for SurfaceProperty:ExteriorNaturalVentedCavity assumes the baffle is a thin metal layer because it was originally implemented for…

    5 votes
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    0 comments  ·  Envelope  ·  Admin →
  7. Window Constructions with Up to 10 Glazing Layers

    Problem: Windows can have more than 4 glazing layers. EnergyPlus currently limits the number of glazing layers to be 4 or less.

    Rationale: New window technologies can have more glazing layers. BIM data may arrive with more than 4 layers and it is difficult to translate to an equivalent window.

    Solution: Allow Construction objects to specify up to 10 WindowMaterial:Glazing objects. Improve code of the Window module to allow more than 4 glazing layers.

    Context: The LBNL Window tool allows up to 10 glazing layers. EnergyPlus model is similar but allows only 4 glazing layers (in the regular/legacy layer-by-layer window…

    3 votes
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    in discussion  ·  0 comments  ·  Envelope  ·  Admin →
  8. Improvements to Moveable Insulation Feature

    Problem: The current movable insulation module is missing two main features: inside transparent insulation and more usable controls. The module already has the ability to model outside transparent and movable insulation. Inside movable insulation is possible with the current model, but this insulation is assumed to be opaque. In addition, the scheduling of movable/transparent insulation is somewhat cumbersome. This is done using a standard EnergyPlus schedule, but since sunrise and sunset vary throughout the year, users must change schedule values often. More intelligent control mechanisms could be implemented to make this easier for users.

    Rationale: The modeling of these features…

    1 vote
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    0 comments  ·  Envelope  ·  Admin →
  9. Support complex window geometry with more than four verices

    Problem: If there are more than four vertices for Fenestration:Detailed object, E+ crashes,thanks to the IDF editor documenting this limitation. BIM tools that automatically generate Fenestration objects from gbXML fail when the windows are hexagonal or adjacent windows are combined in one object with multiple vertices.

    Solution: At the mercy of E+ dev team

    17 votes
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    0 comments  ·  Envelope  ·  Admin →
  10. The number of layers in exterior wall construction

    Currently there is a limitation for the number of layers set at 10. We have recently seen some BIM files containing more than 10 layers (including wall paper, polyethylene, building paper, and multiple sheathing layers). It will be better not to have these limitations crash E+ simulations when the interfaces have no ability to know such limitations.

    3 votes
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    1 comment  ·  Envelope  ·  Admin →
  11. Add Solar Diffusing field to WindowMaterial:SimpleGlazingSystem

    The WindowMaterial:SimpleGlazingSystem is a powerful way to model window constructions using the data typically available to modellers. The one missing property that I know of which is important for daylighting and other analysis is if the window is diffusing or not.

    6 votes
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    in discussion  ·  3 comments  ·  Envelope  ·  Admin →
  12. Thermal bridging

    Problem: EnergyPlus provides no method to describe thermal bridges in envelope components.

    Solution 1: A very basic approximation would be to allow independent parallel path calculations for the same construction (e.g., wood stud and insulation cavity).

    Solution 2: Develop adjustments to the conduction calculations for linear and point thermal bridges, similar to Psi factors.

    36 votes
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    in discussion  ·  10 comments  ·  Envelope  ·  Admin →
  13. Modeling longwave radiant heat exchange between building exterior surfaces and shades

    Longwave radiant heat exchange is a crucial factor in the building exterior surface heat balance analysis. Currently EnergyPlus takes into account the longwave radiant heat exchange between building surface and the environment (i.e., ground, air, and sky), but ignores the heat exchange between the exterior surfaces/shades of adjoining buildings. Modeling such phenomena can lead to more accurate estimations of the exterior surface conditions, especially in urban canyon context, which is essential in predicting the building energy performance and investigating the coupling effect between buildings and microclimate.

    11 votes
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    in discussion  ·  0 comments  ·  Envelope  ·  Admin →
  14. Allow autocalculated dimensions in Construction:FfactorGroundFloor and Construction:CfactorUndergroundWall

    When a surface uses outside boundary condition GroundFCfactorMethod, EnergyPlus currently checks the dimensions (area, perimeter, and height) specified in the corresponding Construction:FfactorGroundFloor and Construction:CfactorUndergroundWall objects. If the dimensions are not close to the dimensions of the surface, then a warning is thrown. It would simplify input if these values could be autocalculated based on the surface dimensions. Reference unmethours [question 10437](https://unmethours.com/question/9954/floor-area-does-not-match-its-construction-area/?answer=10437#post-id-10437)

    1 vote
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    0 comments  ·  Envelope  ·  Admin →
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