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For the narrative report only, the header image is replaced by editing the report template (.dot) file. Please refer to the attached instructions.
Hybrid Degree Day Analysis: Innovative method for computation of energy usage and savings:
• If utility data is available, OptiMiser calculates baseline energy usage from the bills. Then, a weather-normalized load is calculated from the baseline using the Princeton Scorekeeping Method (PRISM) regression modeling technique.
• All savings in OptiMiser are computed relative to this empirical baseline, not from the difference between two theoretical energy use models.
• OptiMiser computes ground coupling heat loss using possibly the best system available for this problematic area of calculation: BASECALC as implemented through BASEIMP which was developed for the HOT 3K modeling project of the Canadian Government.
• OptiMiser’s capacity to simultaneously model all improvements requires that over 40 complete variable base temp-HDD & CDD models are calculated simultaneously with each change in a control.
• Impacts from each improvement affect the variable base temperature and BLC through mechanisms that are estimated using traditional modeling techniques.
• Hourly models are used to model heat pumps, whole house fans, infiltration, and setback thermostats. All of these require hourly modeling to accurately estimate their impact.
• Solar gains through windows are modeled using hourly sun angle positions and hourly TMY3 insolation data. Solar gain computed by this hourly model modifies the base temperature in the OptiMiser analysis.
• By modifying the base temp, OptiMiser takes advantage of the computationally efficient adjustment for usability provided by standard degree day analyses. In contrast, hourly iterative modeling requires much greater computational resources.Attached is OptiMiser’s original DOE Waiver Application, which contains many technical modeling specifications.
The house is in a climate where the cooling load is driven mostly by solar gains. Unless there is extensive voluntary window venting by the occupants (which OptiMiser doesn’t currently model), then there will be many hours during which the outside temperature is lower than the setpoint, but there is still cooling load. During these hours the envelope is actually reducing cooling load and thus improvements to the envelope will increase the cooling load. In some cases this effect will outweigh the savings that the envelope improvement provides during hours when the outside temperature is above the setpoint.
The magnitude of the increase in cooling load will generally be very low and thus not significant from a cost/benefit perspective.
Another thing to consider is that these cases will still usually generate positive demand savings, because peak loads tend to occur during higher outdoor temperatures.
Go to:
Tools > Download New Weather Data
For more information, check out this short video on weather and program updates: https://vimeo.com/45001708.
Yes! OptiMiser has passed Bestest, the industry standard test for accuracy in residential building energy modeling.
OptiMiser is also RESNET HERS accredited. The full HERS accreditation requires passing accuracy test for HVAC and DHW systems in addition to the BESTEST suite, which only tests heating and cooling loads.
Our BESTEST results sheet is attached.
In the Attic tab under Open cavity attic is a parallel path button, || Path.
Click on ||Path and there is a place to change the attic characteristics from vented to unvented.
