Single Zone vs Multi Zone Energy Model for Early Stage Design

Single Zone vs Multi Zone Energy Model for Early Stage Design

single zone vs multi zone

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:

energy use intensity

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:

building parameters

Thermal Zoning:

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

multi zone

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.

single zone

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:

comparison of energy use intensity

Zone 1A - Miami, Florida

PNNL small office Miami

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

PNNL small office houston

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

PNNL small office phoenix

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

PNNL small office atlanta

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

PNNL small office las vegas

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

PNNL small office San Francisco

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

PNNL small office Baltimore

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

PNNL small office Albuquerque

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

PNNL small office Seattle

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

PNNL small office Chicago

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

PNNL small office Denver

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

PNNL small office Minneapolis

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

PNNL small office Helena

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

PNNL small office Duluth

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

PNNL small office Fairbanks

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%.

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