Introduction

The purpose of this study is to reduce the time and effort put into remodeling thermal zones whenever there is a small or big change in the building design made by the project team while maintaining the accuracy level. The main focus is on the sensitivity of building geometry and thermal zoning while keeping other parameters constant. The study is conducted using the small office building prototype provided by Pacific National Northwest Laboratory (PNNL).

Key Observations:

The Energy Usage Intensity (EUI) is compared for the small office model which has 4 perimeter zones and 1 core zone to the model which has only 1 zone. The models were simulated for all of the ASHRAE climate zones to obtain the results. The average overall EUI difference of 2.82% was observed between five zone model vs single zone model. The maximum and minimum percentage difference of 3.92 and 1.59 for overall EUI was recorded for Denver, CO (ASHRAE Climate Zone 5B) and San Francisco, CA (ASHRAE Climate Zone 3C) respectively.

Furthermore,  to study the sensitivity of glazing percentage on zone lumping the glazing percentage for every orientation was increased by 20%. After running the simulations, the average overall EUI difference of 4.23% was observed between five zone model vs single zone model for all climate zones. The maximum and minimum percentage difference of 5.7 and 2.88 for overall EUI was recorded for Denver, CO (ASHRAE Climate Zone 5B) and San Francisco, CA (ASHRAE Climate Zone  3C) respectively.

Methodology:

Building Parameters:

The selected building is a small office prototype described by Pacific Northwest National Laboratory (PNNL). Some of the building parameters are mentioned below:

Thermal Zoning:

The thermal zoning for the prototype building model can be seen in the attached image.

Figure 1 Thermal Zoning for Small Office according to PNNL

There are 4 perimeter zones and 1 core zone. The perimeter depth modeled is 16.4 ft on each side. The thermal zoning can be a complex process depending upon the nature of building design. The conceptual design decisions usually involve changes in the geometry of the building, window to wall ratio (WWR) and envelope properties.

The proposed thermal zoning modifies the building to consist only on single zone instead of five different zones. This will significantly reduce the time spent in remodeling as there are lesser number of zones to be changed.

Figure 2 Proposed Thermal Zoning for Small Office

Comparison of Energy Usage Intensity:

The different cities used to perform the comparison between single zone and five zone small office models are listed below:

Zone 1A - Miami, Florida

The EUI difference between 5 zone model and single zone model was observed to be 2.84% for Miami, Florida. When the glazing was increased by 20% for all orientations the EUI difference increased to 3.58%.

Zone 2A - Houston, Texas

The EUI difference between 5 zone model and single zone model was observed to be 2.48% for Houston, Texas. When the glazing was increased by 20% for all orientations the EUI difference increased to 3.32%.

Zone 2B - Phoenix, Arizona

The EUI difference between 5 zone model and single zone model was observed to be 3.35% for Phoenix, Arizona. When the glazing was increased by 20% for all orientations the EUI difference increased to 4.25%.

Zone 3A - Atlanta, Georgia

The EUI difference between 5 zone model and single zone model was observed to be 2.78% for Atlanta, Georgia. When the glazing was increased to 20% for all orientations the EUI difference increased to 3.84%.

Zone 3B - Las Vegas, Nevada

The EUI difference between 5 zone model and single zone model was observed to be 3.45% for Las Vegas, Nevada. When the glazing was increased to 20% for all orientations the EUI difference increased to 4.48%.

Zone 3C - San Francisco, California

The EUI difference between 5 zone model and single zone model was observed to be 1.59% for San Francisco, California. When the glazing was increased to 20% for all orientations the EUI difference increased to 2.88%.

Zone 4A - Baltimore, Maryland

The EUI difference between 5 zone model and single zone model was observed to be 2.92% for Baltimore, Maryland. When the glazing was increased to 20% for all orientations the EUI difference increased to 4.41%.

Zone 4B - Albuquerque, New Mexico

The EUI difference between 5 zone model and single zone model was observed to be 3.57% for San Francisco, California. When the glazing was increased to 20% for all orientations the EUI difference increased to 4.88%.

Zone 4C - Seattle, Washington

The EUI difference between 5 zone model and single zone model was observed to be 2.12% for Seattle, Washington. When the glazing was increased to 20% for all orientations the EUI difference increased to 3.35%.

Zone 5A - Chicago, Illinois

The EUI difference between 5 zone model and single zone model was observed to be 2.55% for Chicago, Illinois. When the glazing was increased to 20% for all orientations the EUI difference increased to 4.35%.

Zone 5B - Denver, Colorado

The EUI difference between 5 zone model and single zone model was observed to be 3.92% for Denver, Colorado. When the glazing was increased to 20% for all orientations the EUI difference increased to 5.70%.

Zone 6A - Minneapolis, Minnesota

The EUI difference between 5 zone model and single zone model was observed to be 2.77% for Minneapolis, Minnesota. When the glazing was increased to 20% for all orientations the EUI difference increased to 4.88%.

Zone 6B - Helena, Montana

The EUI difference between 5 zone model and single zone model was observed to be 3.15% for Helena, Montana. When the glazing was increased to 20% for all orientations the EUI difference increased to 5.19%.

Zone 7 - Duluth, Minnesota

The EUI difference between 5 zone model and single zone model was observed to be 2.42% for Duluth, Minnesota. When the glazing was increased to 20% for all orientations the EUI difference increased to 4.63%.

Zone 8 - Fairbanks, Alaska

The EUI difference between 5 zone model and single zone model was observed to be 2.40% for Fairbanks, Alaska. When the glazing was increased to 20% for all orientations the EUI difference increased to 3.66%.