Unmet Hours - RSS feedhttps://unmethours.com/questions/Question-and-Answer Resource for the Building Energy Modeling CommunityenWed, 04 Dec 2019 13:04:56 -0600How are unmet hours calculated in Sefaira and are they related to dry buld temperature?https://unmethours.com/question/41612/how-are-unmet-hours-calculated-in-sefaira-and-are-they-related-to-dry-buld-temperature/How does Sefaira calculate 'unmet hours'? I understand that this is the percentage of the number of hours in a year in which more than one room in the building is not "comfortable". I assume that "comfortable" is defined by the temperature range (rather than the setback range) of the HVAC system. What measure of thermal comfort is calculated for each room for comparison to the temperature range?
Furthermore, is there a relationship between unmet hours and dry bulb temperature?
I have been unable to find information about this in the offical Sefaira doccumentation and any help would be greatly appreciated! There are lots of tutorials that talk about thermal comfort but they all focus on dry bulb, operative temperature or ASHRAE.
Angusarchy1Wed, 04 Dec 2019 13:04:56 -0600https://unmethours.com/question/41612/How do I simulate temperatures in a naturally ventilated greenhouse, and potential heat transfer to connected building?https://unmethours.com/question/36130/how-do-i-simulate-temperatures-in-a-naturally-ventilated-greenhouse-and-potential-heat-transfer-to-connected-building/I'm looking to model a rooftop greenhouse on top of a 3 storey hotel building. We are wanting to look at the value of using excess heat from the greenhouse to heat spaces in the building below. The greenhouse will be naturally ventilated and unheated. I've been attempting to model the temperature inside the greenhouse using energyplus (editing a .idf file exported from Sefaira) but it's been giving some pretty odd results. I have a feeling my issue may be in allowing for natural ventilation. The way I currently have it modelled the internal temperature in summer seems reasonable, peaking out at about 37-40 deg C depending on U-value of the glass, however in winter the internal temperature in the greenhouse drops below the outside temperature at some points which I would have thought impossible? I'm using "Zone Mean Air Temperature" as the temperature output variable.
For the natural ventilation setup I have the venting availability set to 1 constantly, the ventilation temperature setpoint set to 22.5 deg C constantly, and the temperature difference for maximum and minimum venting open factor set to 5 and 0.5 respectively. Does this seem right?
Secondly, does anyone know how I might be able to model the reduction in heating that could be achieved by using excess heat from the greenhouse to heat spaces below?
Thanks!willyoungMon, 10 Dec 2018 01:42:40 -0600https://unmethours.com/question/36130/Increased WWR = Decreased Peak Tonnage?https://unmethours.com/question/33213/increased-wwr-decreased-peak-tonnage/Generated the below Sefaira response curve for window-wall ratio versus peak cooling coil load (tons), in yellow and Annual electricity consumption (kWh) in red...
The linear increase in annual energy I get... But the weird cooling coil response curve, I’m having trouble wrapping my head around. Thoughts?
![Weird Response Curve](https://image.ibb.co/gOa0rK/Sefaira.png)sgudemanTue, 31 Jul 2018 12:53:25 -0500https://unmethours.com/question/33213/Natural ventilation set points in EnergyPlushttps://unmethours.com/question/30172/natural-ventilation-set-points-in-energyplus/I am trying to model a building with natural ventilation in EnergyPlus (with an idf file from a Sefaira model).
I have set the maximum outdoor and indoor temperatures in the AvailabilityManager:HybridVentilation to 21-24C (this may not be the right place to do this?). The "windowventsched" for each space type appears to have one temperature assigned for each hour (17.0C until 7am, 32.5 after for some space types, 22.5C all day for some). These numbers don't seem to reflect my set points in Sefaira.
Basically -
1. is "schedule:compact/xxxxx space type windowventsched" the right place to control window opening for natural ventilation?
2. how do the set points work (only appears to be one number not upper and lower?)
3. does anyone have any recommendations for what appropriate set points may be (trying to maximise fanger PMV comfort)?willyoungTue, 06 Mar 2018 18:25:40 -0600https://unmethours.com/question/30172/What are the underlying resources for simulation using Sefaira's new plug in to REVIT?https://unmethours.com/question/306/what-are-the-underlying-resources-for-simulation-using-sefairas-new-plug-in-to-revit/Sefaira's website states the following "Real Time Analysis in Revit enables design teams to achieve their vision of high performance buildings in a rigorous and efficient manner." I am interested in know how rigorous this tool is and what simulation techniques/engine it is based on. When is it most appropriate to use for a project?
see: http://sefaira.com/resources/sefaira-for-revit-now-includes-real-time-analysis/
Shanta TuckerMon, 29 Sep 2014 07:53:09 -0500https://unmethours.com/question/306/