Modelling, Design, and Optimization of Net-Zero Energy Buildings E-Book

• Herausgeber: Wiley-VCH
• Kategorie: Fachliteratur
• Serie: Solar Heating and Cooling
• Sprache: Englisch

Seitenzahl: 643

Veröffentlichungsjahr: 2015

Beschreibung

Building energy design is currently going through a period of major changes. One key factor of this is the adoption of net-zero energy as a long term goal for new buildings in most developed countries. To achieve this goal a lot of research is needed to accumulate knowledge and to utilize it in practical applications. In this book, accomplished international experts present advanced modeling techniques as well as in-depth case studies in order to aid designers in optimally using simulation tools for net-zero energy building design. The strategies and technologies discussed in this book are, however, also applicable for the design of energy-plus buildings. This book was facilitated by International Energy Agency's Solar Heating and Cooling (SHC) Programs and the Energy in Buildings and Communities (EBC) Programs through the joint SHC Task 40/EBC Annex 52: Towards Net Zero Energy Solar Buildings R&D collaboration. After presenting the fundamental concepts, design strategies, and technologies required to achieve net-zero energy in buildings, the book discusses different design processes and tools to support the design of net-zero energy buildings (NZEBs). A substantial chapter reports on four diverse NZEBs that have been operating for at least two years. These case studies are extremely high quality because they all have high resolution measured data and the authors were intimately involved in all of them from conception to operating. By comparing the projections made using the respective design tools with the actual performance data, successful (and unsuccessful) design techniques and processes, design and simulation tools, and technologies are identified. Written by both academics and practitioners (building designers) and by North Americans as well as Europeans, this book provides a very broad perspective. It includes a detailed description of design processes and a list of appropriate tools for each design phase, plus methods for parametric analysis and mathematical optimization. It is a guideline for building designers that draws from both the profound theoretical background and the vast practical experience of the authors.

Leseprobe

CONTENTS

Cover

Related Titles

Title Page

Copyright

About the Editors

List of Contributors

Preface

Foreword

Acknowledgments

Chapter 1: Introduction

1.1 Evolution to Net-Zero Energy Buildings

1.2 Scope of this Book

References

Chapter 2: Modeling and Design of Net ZEBs as Integrated Energy Systems

2.1 Introduction

2.2 Renewable Energy Generation Systems/Technologies Integrated in Net ZEBs

References

Chapter 3: Comfort Considerations in Net ZEBs: Theory and Design

3.1 Introduction

3.2 Thermal Comfort

3.3 Daylight and Visual Comfort

3.4 Acoustic Comfort

3.5 Indoor Air Quality

3.6 Conclusion

References

Chapter 4: Net ZEB Design Processes and Tools

4.1 Introduction

4.2 Integrating Modeling Tools in the Net ZEB Design Process

4.3 Net ZEB Design Tools, Model Resolution, and Design Methods

4.4 Conclusion

References

Chapter 5: Building Performance Optimization of Net Zero-Energy Buildings

5.1 Introduction

5.2 Optimization Fundamentals

5.3 Application of Optimization: Cost-Optimal and Nearly Zero-Energy Building

5.4 Application of Optimization: A Comfortable Net-Zero Energy House

5.5 Conclusion

References

Chapter 6: Load Matching, Grid Interaction, and Advanced Control

6.1 Introduction

6.2 LMGI Indicators

6.3 Strategies for Predictive Control and Load Management

6.4 Development of Models for Controls

6.5 Conclusion

References

Chapter 7: Net ZEB Case Studies

7.1 Introduction

7.2 ÉcoTerra

7.3 Leaf House

7.4 NREL RSF

7.5 Enerpos

7.6 Conclusions

Acknowledgment

References

Chapter 8: Conclusion, Research Needs, and Future Directions

8.1 Net ZEB Modeling, Design, and Simulation

8.2 Future Directions and Research Needs

Glossary

Index

EULA

List of Tables

Table 1.1

Table 1.2

Table 2.1

Table 3.1

Table 3.2

Table 3.3

Table 3.4

Table 3.5

Table 3.6

Table 3.7

Table 4.1

Table 4.2

Table 4.3

Table 4.4

Table 5.1

Table 5.2

Table 5.3

Table 6.1

Table 6.2

Table 7.1

Table 7.2

Table 7.3

Table 7.4

Table 7.5

Table 7.6

Table 7.7

Table 7.8

Table 7.9

Table 7.10

Table 7.11

Table 7.12

Table 7.13

Table 7.14

Table 7.15

Table 7.16

Table 7.17

Table 7.18

Table 7.19

Table 7.20

Table 7.21

Table 7.22

List of Illustrations

Fig. 1.1

Fig. 2.1

Fig. 2.2

Fig. 2.3

Fig. 2.4

Fig. 2.5

Fig. 2.6

Fig. 2.7

Fig. 2.8

Fig. 2.9

Fig. 2.10

Fig. 2.11

Fig. 2.12

Fig. 2.13

Fig. 2.14

Fig. 2.15

Fig. 2.16

Fig. 2.17

Fig. 2.18

Fig. 2.19

Fig. 2.20

Fig. 2.21

Fig. 2.22

Fig. 2.23

Fig. 2.24

Fig. 2.25

Fig. 2.26

Fig. 3.1

Fig. 3.2

Fig. 3.3

Fig. 3.4

Fig. 3.5

Fig. 3.6

Fig. 4.1

Fig. 4.2

Fig. 4.3

Fig. 4.4

Fig. 4.5

Fig. 4.6

Fig. 4.7

Fig. 4.8

Fig. 4.9

Fig. 4.10

Fig. 4.11

Fig. 4.12

Fig. 4.13

Fig. 4.14

Fig. 4.15

Fig. 4.16

Fig. 4.17

Fig. 4.18

Fig. 4.19

Fig. 4.20

Fig. 4.21

Fig. 4.22

Fig. 4.23

Fig. 4.24

Fig. 4.25

Fig. 4.26

Fig. 4.27

Fig. 4.28

Fig. 5.1

Fig. 5.2

Fig. 5.3

Fig. 5.4

Fig. 5.5

Fig. 5.6

Fig. 5.7

Fig. 5.8

Fig. 5.9

Fig. 5.10

Fig. 5.11

Fig. 5.12

Fig. 5.13

Fig. 5.14

Fig. 5.15

Fig. 5.16

Fig. 6.1

Fig. 6.2

Fig. 6.3

Fig. 6.4

Fig. 6.5

Fig. 6.6

Fig. 6.7

Fig. 6.8

Fig. 6.9

Fig. 6.10

Fig. 6.11

Fig. 6.12

Fig. 7.1

Fig. 7.2

Fig. 7.3

Fig. 7.4

Fig. 7.5

Fig. 7.6

Fig. 7.7

Fig. 7.8

Fig. 7.9

Fig. 7.10

Fig. 7.11

Fig. 7.12

Fig. 7.13

Fig. 7.14

Fig. 7.15

Fig. 7.16

Fig. 7.17

Fig. 7.18

Fig. 7.19

Fig. 7.20

Fig. 7.21

Fig. 7.22

Fig. 7.23

Fig. 7.24

Fig. 7.25

Fig. 7.26

Fig. 7.27

Fig. 7.28

Fig. 7.29

Fig. 7.30

Fig. 7.31

Fig. 7.32

Fig. 7.33

Fig. 7.34

Fig. 7.35

Fig. 7.36

Fig. 7.37

Fig. 7.38

Fig. 7.39

Fig. 7.40

Fig. 7.41

Fig. 7.42

Fig. 7.43

Fig. 7.44

Fig. 7.45

Fig. 7.46

Fig. 7.47

Fig. 7.48

Fig. 7.49

Fig. 7.50

Fig. 7.51

Fig. 7.52

Fig. 7.53

Fig. 7.54

Fig. 7.55

Fig. 7.56

Fig. 7.57

Fig. 7.58

Fig. 7.59

Fig. 7.60

Fig. 7.61

Fig. 7.62

Fig. 7.63

Fig. 7.64

Fig. 7.65

Fig. 7.66

Fig. 7.67

Fig. 7.68

Fig. 7.69

Fig. 7.70

Fig. 7.71

Fig. 7.72

Fig. 7.73

Fig. 7.74

Fig. 7.75

Fig. 7.76

Fig. 7.77

Fig. 7.78

Fig. 7.79

Fig. 7.80

Fig. 7.81

Fig. 7.82

Fig. 7.83

Guide

Cover

Table of Contents

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Modeling, Design, and Optimization of Net-Zero Energy Buildings

Edited by

Andreas Athienitis

William O'Brien

All books published by Ernst & Sohn are carefully produced. Nevertheless, authors, editors, and publisher do not warrant the information contained in these books, including this book, to be free of errors. Readers are advised to keep in mind that statements, data, illustrations, procedural details or other items may inadvertently be inaccurate.

Library of Congress Card No.: applied for

British Library Cataloguing-in-Publication Data

A catalogue record for this book is available from the British Library.

Bibliographic information published by the Deutsche Nationalbibliothek

The Deutsche Nationalbibliothek lists this publication in the Deutsche Nationalbibliografie; detailed bibliographic data are available on the Internet at <http://dnb.d-nb.de>.

© 2015 Wilhelm Ernst & Sohn, Verlag für Architektur und technische Wissenschaften GmbH & Co. KG, Rotherstraße 21, 10245 Berlin, Germany

All rights reserved (including those of translation into other languages). No part of this book may be reproduced in any form – by photoprinting, microfilm, or any other means – nor transmitted or translated into a machine language without written permission from the publishers. Registered names, trademarks, etc. used in this book, even when not specifically marked as such, are not to be considered unprotected by law.

Print ISBN: 978-3-433-03083-7

ePDF ISBN: 978-3-433-60463-2

ePub ISBN: 978-3-433-60465-6

Mobi ISBN: 978-3-433-60464-9

oBook ISBN: 978-3-433-60462-5

About the Editors

Dr. Andreas K. Athienitis is a Professor of Building Engineering and holds a Research Chair in Integration of Solar Energy Systems into Buildings and a NSERC/Hydro Quebec Industrial Chair at Concordia University, Montreal. He is the Scientific Director of the Canadian NSERC Smart Net-zero Energy Buildings Strategic Research Network (2011–2016) and the founding Director of the NSERC Solar Buildings Research Network (2005–2010). He was a sub-task co-leader for IEA SHC Task 40/EBC Annex 52 (“Towards Net-Zero Energy Solar Buildings”). He is author of more than 200 refereed papers and several books and book chapters in solar buildings and building energy systems. Prof. Athienitis is a Fellow of the Canadian Academy of Engineering and a contributing author of the Intergovernmental Panel for Climate Change (IPCC).

Dr. William O'Brien is an Assistant Professor in the Architectural Conservation and Sustainability Engineering program at Carleton University, Ottawa. He is the principal investigator of the Human Building Interaction Laboratory, which consists of a multidisciplinary team of researchers that are designing buildings and building controls that incorporate human factors. He has published over 40 peer-reviewed papers. He was a sub-task co-leader for IEA SHC Task 40/EBC Annex 52 (“Towards Net-Zero Energy Solar Buildings”) and now, IEA EBC Annex 66 (“Definition and Simulation of Occupant Behavior in Buildings”).

Production Editor

Samson Yip is a Senior Architect at Saia Barbarese Topouzanov Architects in Montreal specializing in institutional architecture. He is completing a Master of Applied Science (Building Engineering) degree at Concordia University, Montreal, within the Canadian NSERC Smart Net-zero Energy Buildings Strategic Research Network. He was a participant in the IEA SHC Task 40/EBC Annex 52 (“Towards Net-Zero Energy Solar Buildings”). Prior to that, he was an Adjunct Professor at the School of Architecture, McGill University, Montreal.

List of Contributors

Andreas K. Athienitis

Concordia University

1455 de Maisonneuve Blvd. West

Montreal, QC H3G 1M8

Canada

Shady Attia

Université de Liège

Sustainable Buildings Design Lab

1 Chemin des Chevreuils

Sart Tilman B52/3

4000 Liège

Belgium

Josef Ayoub

CanmetENERGY

Natural Resources Canada

Government of Canada

1615 Lionel-Boulet Blvd.

Varennes, QC J3X 1S6

Canada

Paul Bourdoukan

Sorane France

25 B Quai Jean Baptiste Simon

69270 Fontaines sur Saone

France

Scott Bucking

McMaster University

1280 Main Street West

Hamilton, ON L8S 4L8

Canada

José A. Candanedo

CanmetENERGY

Natural Resources Canada

Government of Canada

1615 Lionel-Boulet Blvd.

Varennes, QC J3X 1S6

Canada

Salvatore Carlucci

NTNU Norwegian University of Science and Technology

Høgskoleringen 7A

7491 Trondheim

Norway

Maurizio Cellura

University of Palermo

Viale delle Scienze, Building 9

90128 Palermo

Italy

Yuxiang Chen

Concordia University

1455 de Maisonneuve Blvd. West

Montreal, QC H3G 1M8

Canada

Véronique Delisle

CanmetENERGY

Natural Resources Canada

Government of Canada

1615 Lionel-Boulet Blvd.

Varennes, QC J3X 1S6

Canada

Francois Garde

University of La Réunion

PIMENT Laboratory

117, rue Général Ailleret

97430 Le Tampon

Reunion Island

France

Francesco Guarino

University of Palermo

Viale delle Scienze, Building 9

90128 Palermo

Italy

Ala Hasan

VTT Technical Research Centre of Finland

Tekniikantie 4A

02044 Espoo

Finland

Mohamed Hamdy Hassan

Eindhoven University of Technology

Department of the Built Environment, Building Physics and Services

P.O. Box 513

5600 MB Eindhoven

The Netherlands

and

Aalto University School of Engineering

Department of Energy Technology

P.O. Box 14400

FI-00076 Aalto

Finland

Konstantinos Kapsis

Concordia University

1455 de Maisonneuve Blvd. West

Montreal, QC H3G 1M8

Canada

Aurélie Lenoir

University of Reunion Island

PIMENT Laboratory

117, rue du Général Ailleret

97430 Le Tampon

Reunion Island

France

Davide Nardi Cesarini

Loccioni Group

Via Fiume 16

60030 Angeli di Rosora

Italy

William O'Brien

Carleton University

1125 Colonel By Drive

3432 Mackenzie Building

Ottawa, ON K1S 5B6

Canada

Lorenzo Pagliano

Politecnico di Milano

end-use Efficiency Research Group (eERG)

via Lambruschini, 4

20156 Milano

Italy

Jaume Salom

Catalonia Institute for Energy Research, IREC

Jardins de les Dones de Negre, 1

8930 Sant Adrià de Besòs

Spain

Joakim Widén

Uppsala University

Department of Engineering Sciences

Lagerhyddsvagen 1

75121 Uppsala

Sweden

Samson Yip

Concordia University

Dept. of Building, Civil and Environmental Engineering

1455 de Maisonneuve West

EV 6.159

Montréal, QC H3G 1M8

Canada

Preface

Andreas Athienitis and WilliamO' Brien

Just over five years ago, approximately 60 international experts of the International Energy Agency – Solar Heating and Cooling Task 40/Energy in Buildings and Communities (EBC) Annex 52: Towards Net-zero Energy Solar Buildings (“T40A52”) met in Montreal at Concordia University for the first official experts meeting. Many of the experts were in for a surprise as they discovered the diversity of international perspectives on net-zero energy buildings (Net ZEBs) – including definitions, official building standards, business and legal aspects, and design strategies. Over the following five years, the experts traveled to an additional nine meeting destinations and became immersed in the local building design cultures, providing us with a valuable international perspective on Net ZEBs and giving us the pleasure of meeting in several Net ZEBs (several of which were meeting venues and are discussed in depth in this book).

The objective of this book is to present a wide perspective on Net ZEB modeling, design, and related issues, while also providing substantial depth for designers and graduate students. The book was written by a total of 22 authors from seven countries of diverse climates with experts from both industry and academia/research. The book begins with fundamentals of modeling, strategies and technologies required to reach net-zero energy including many methods to quantify performance. As emphasized by T40A52, comfort is a fundamental aspect of Net ZEB and not an afterthought; therefore, a full chapter was devoted to thermal, visual, and acoustic comfort and indoor air quality. The following two chapters are devoted to design, modeling, simulation, and optimization of Net ZEBs with several examples. It was realized early in T40/A52 that research on Net ZEBs must encapsulate interactions with electrical grids since net-zero energy definitions are primarily focused on energy balances; thus, a whole chapter is devoted to this issue. In the second to last chapter, four detailed Net ZEB case studies are described in detail and linked to earlier fundamental chapters, including energy performance, comfort, design intent versus real operation, and lessons learned. Finally, redesign of archetypes based on the case studies are presented.

Andreas Athienitis, Ph. D., P. Eng., FCAENSERC/Hydro Quebec IndustrialChair & Concordia Research ChairScientific Director, NSERC Smart Net-zero EnergyBuildings Strategic Research Network &Director, Concordia Centre for Zero Energy Building StudiesConcordia University, Montreal, Canada

William O'Brien, PhDCivil and Environmental EngineeringCarleton University, Ottawa, Canada

Foreword

Josef Ayoub

This book was produced in the context of the collaboration between approximately 75 national experts from 19 nations in Europe, North America, Oceania, and Southeast Asia of the International Energy Agency (IEA), in the framework of the programs on Solar Heating and Cooling (SHC Task 40) and Energy in Buildings and Communities (EBC Annex 52), under the title “Towards Net-Zero Energy Solar Buildings.” T40A52 sought to study current net-zero, near-net-zero and very low energy buildings and to develop a common understanding of a harmonized international definitions framework, tools, innovative solutions, and industry guidelines to support the conversion of the Net ZEB concept from an idea into practical reality in the marketplace.

This Task/Annex pursued optimal integrated design solutions that provided a good indoor environment for both heating and cooling situations. The process recognized the importance of optimizing a design to meet the functional requirement, reducing loads, and designing energy systems that pave the way for seamless incorporation of renewable energy innovations, as they become cost effective. To achieve these results, the National Experts met twice annually at a hosting member country to coordinate the R&D activities and advance the work plan comprised of the following four major activities:

Subtask A dealt with establishing an internationally agreed understanding on Net ZEBs based on a common methodology. This was done by reviewing and analyzing existing Net ZEB definitions and data with respect to the demand and the supply side; studying grid interaction (power/heating/cooling) and time-dependent energy mismatch analysis; developing a harmonized international definition framework for the Net ZEB concepts considering large-scale implications, exergy, and credits for grid interaction (power/heating/cooling); and, developing a monitoring, verification and compliance guide for checking the annual balance in practice (energy, emissions, and costs) harmonized with the definition;

Subtask B aimed to identify and refine design approaches and tools to support industry adoption. This was done by conducting work along four major R&D streams: (i) in documenting and analyzing processes and tools currently being used to design Net ZEBs and under development by participating countries; (ii) assessing gaps, needs, and problems to inform simulation engine and detailed design tool developers of priorities for Net ZEBs; (iii) qualitative and quantitative benchmarking of selected tools; and (iv) selecting four case study buildings to conduct a detailed analysis of simulated/designed vs. actual performance, and proposing the redesign/optimization of these buildings;

Subtask C focused on developing and testing innovative, whole building net-zero solution sets for cold, moderate, and hot climates with exemplary architecture and technologies that would be the basis for demonstration projects and international collaboration. This was achieved by documenting and analyzing current Net ZEBs designs and technologies, benchmarking with near Net ZEBs and other very low energy buildings (new and existing), for cold, moderate, and hot climates considering sustainability, economy, and future prospects using a projects database, literature review, and practitioner input (workshops); developing and assessing case studies and demonstration projects in close cooperation with practitioners; investigating advanced integrated design concepts and technologies in support of the case studies, demonstration projects, and solution sets; and developing Net ZEB solution sets and guidelines with respect to building types and climate, and to document design options in terms of market application;

Subtask D was crosscutting work that focused on dissemination to support knowledge transfer and market adoption of Net ZEBs on a national and international level. This was accomplished by establishing a Net ZEB webpage within the IEA SHC/EBC Programmes' framework and a database that can be expanded and updated with the latest projects and experiences; transferring the outputs (reports, sourcebooks, guidelines, other) to national policy groups, industry associations, utilities, academia, and funding programs; participating in national and international workshop, seminars, and industry exhibitions highlighting the results and activities of the Task/Annex contributing high-quality technical articles and features in journals to stimulate market adoption; and, establishing an education network of highly qualified people that will continue the work in the field for their future endeavors.

I am pleased to present the research results of Subtask B compiled in this volume of work entitled “Modeling, Design, and Optimization of Net-Zero Energy Buildings,” as a major accomplishment in this field of research. Building energy design is currently going through a period of major changes driven largely by three key factors and related technological developments: (i) the increasingly widespread adoption in most OECD member countries and by influential engineering societies, such as ASHRAE, of net-zero energy as a long-term goal for new buildings; (ii) the need to reduce the peak electricity demand for buildings through optimal operation; and (iii) the need to efficiently integrate advanced energy technologies into buildings, such as photovoltaic/thermal systems, windows with semitransparent photovoltaic glazing, controlled shading/daylighting devices, and integrated thermal storage. It encapsulates the many and varied concepts of designing and optimizing net-zero energy buildings by government research organizations, international and regional research centers, academia, and industry. I am confident this book will find many interested readers.

Josef AyoubOperating Agent, IEA SHC Task 40/EBC Annex 52Senior Planning Advisor, Energy Science & TechnologyCanmetENERGY | Natural Resources Canada Government of Canadatask40.iea-shc.org/

Acknowledgments

Funding

The Government of Canada provided partial funding for this work under two major programs: the Program of Energy Research and Development (PERD), a federal interdepartmental program operated by the Department of Natural Resources Canada funded the position of the Operating Agent to coordinate the work and lead this international network; and the EcoENERGY Innovation Initiative (EcoEII) aimed at supporting energy technology innovation to produce and use energy in a cleaner and more efficient way, funded the R&D work and participation of the National Experts from Canada in this Task/Annex.

The Natural Sciences and Engineering Research Council of Canada (NSERC) through the NSERC Smart Net-zero Energy Buildings strategic Research Network (SNEBRN) funded related research on Net ZEBs by Andreas Athienitis, Scientific Director of SNEBRN and Professor of Building Engineering at Concordia University, and his students, several of whom contributed to this book and are listed as contributors. Concordia University hosted the first and last meetings of this 5-year Task.

1Introduction

Andreas Athienitis, William O'Brien, and Josef Ayoub

1.1 Evolution to Net-Zero Energy Buildings

Buildings have evolved over time from largely passive systems into structures with increasingly high levels of environmental control, partly through the addition of man-made insulation materials, such as fiberglass and polystyrene. The adoption of electric lighting in early twentieth century buildings, contributed to a reduction in window areas and reliance on artificial lighting, particularly in the period from 1950 to 1970. But in the 1980s, the development and acceptance of sealed double-glazed windows with an insulating airspace, or insulating windows with special coatings to reduce heat transfer and optimize transmission of solar radiation (Athienitis and Santamouris, 2002), led to the adoption of larger fenestration areas (up to 60% of the façade area) in both the residential and commercial buildings. These large fenestration areas – as much as 90% of the façade area – lead to high heating and cooling energy consumption. Thus, fenestration and daylighting significantly influence the design of commercial buildings. The drivers of the design of residential buildings are shifting from space conditioning to appliances, lighting, and integrated energy systems, as building envelopes and HVAC become more efficient and passive techniques are employed.

Since the early 1990s the potential of solar radiation incident on building surfaces to satisfy all their energy needs has contributed to the idea of net-zero energy buildings gaining widespread acceptance as a technically feasible long-term goal (for most regions). A net-zero energy building (Net ZEB) is normally defined as one that, in an average year, produces as much energy (electrical plus thermal) from renewable energy sources as it consumes. When the energy production is on-site the Net ZEB definition is most strict.

The visible part of the solar spectrum (nearly half of total solar radiation) is useful as daylight. Almost all of solar radiation can be converted to useful heat for space heating, as well as other useful purposes, such as heating water and drying clothes, or even solar cooling using passive and active solar systems (International Solar Energy Society (ISES), 2001). Another solar technology – photovoltaic (PV) – that converts solar radiation to electricity has recently experienced significant advances and dramatic reductions in cost (almost 90% cost reduction per watt of generating capacity in the last 10 years). Both technologies can be integrated and optimized for combined heat and power generation to advance buildings toward net-zero energy consumption.

Most inhabited areas receive significant amounts of sunshine that enable the design of technically feasible Net ZEBs with current solar and energy efficiency technologies. For example, in Canada between latitudes 40–53 °N where most of Canada's population lives, a suitably oriented façade or roof on a typical building receives up to ∼6 kWh/m2 per day, and the incident solar energy often exceeds total building energy consumption. Photovoltaic panels integrated on the roof and façade can typically convert 6–20% of the sun's energy into electricity, and 50–70% of the remainder can be extracted as heat from the PV panels, while 10 to 30% can be utilized for daylighting in semitransparent systems. Combined solar energy utilization efficiencies on the order of 80% can be achieved if proper integration strategies are implemented and nearly the full spectrum of solar radiation can be utilized as daylight, useful heat, or electricity.

The energy generation function in Net ZEBs using solar energy – as daylight, useful heat, and electricity – requires a transformation of the way buildings are designed and operated so as to be cost effective and affordable. The key challenges for smart Net ZEBs to overcome are summarized in Table 1.1 for each of the four major building subsystems where the current situation is contrasted with the expected characteristics of Net ZEBs. In addition, the integration of design with operation is considered.

Table 1.1 Challenges for smart Net ZEBs

Building systems, design and operation

Current buildings

Smart Net ZEBs

Building fabric/envelope

Passive, not designed as an energy system

Optimized for passive design and integration of active solar systems

Heating, ventilation and air conditioning (HVAC)

Large oversized systems

Small HVAC systems optimally controlled; integrated with solar systems, combined heat and power; communities: seasonal storage and district energy

Solar systems/renewables, generation

No systematic integration – an afterthought

Fully integrated: daylighting, solar thermal, photovoltaics, hybrid solar, geothermal systems, biofuels, linked with smart microgrids

Building automation systems

Building automation systems not used effectively

Predictive building control to optimize comfort and energy performance; online demand prediction/peak demand reduction

Design and operation

The design and operation of buildings are typically not considered together

Design and operation of buildings fully integrated and optimized together subject to satisfying comfort; integrated design of the above four building subsystems

1.1.1 Net ZEB Concepts

The convergence of the need for innovation and the requirement for drastic reductions in energy use and greenhouse gas (GHG) emissions in the building sector provides a unique opportunity to transform the way buildings and their energy systems are conceived. Demand abatement through passive design, energy efficiency, and conservation measures needs to be simultaneously considered with integration of solar systems and on-site generation of useful heat and electricity using a whole building approach.

Building energy design is currently undergoing a period of major changes driven largely by three key factors and related technological developments:

The adoption in many developed countries, and by influential professional societies, such as ASHRAE, of net-zero energy [3] as a long-term goal for new buildings;

The need to reduce the peak electricity demand from buildings through optimal operation, thus reducing the need to build new central power plants that often use fossil fuels; and,

The decreasing cost of energy-generating technologies, such as photovoltaics, which enables building-integrated energy systems to be more affordable and competitive. This is coupled with increasing costs of energy from traditional energy sources (e.g., fossil fuels).

A key requirement of high performance building design is the need for rigorous design and operation of a building as an integrated energy system that must have a good indoor environment suited to its functions. In addition to the extensive array of HVAC, lighting, and automation technologies developed over the last 100 years, many new building envelope technologies have been established, such as vacuum insulation panels and advanced fenestration systems (e.g., electrochromic coatings for so-called smart windows), as well as solar thermal technologies for heating and cooling, and solar electric or hybrid systems and combined heat and power (CHP) technologies. A high-performance building may be designed with optimal combinations of traditional and advanced technologies depending on its function and on climate.

Solar gain and daylight control through smart window systems, in which the transmission of solar radiation can be actively controlled, remain a challenge in building design and operation because of the simultaneous effects on instantaneous and delayed heating/cooling loads, and on thermal and visual comfort. Solar gains may be controlled through a combination of passive and active measures – with the passive measures employed during design and active measures, such as positioning of motorized venetian blinds during operation. Since solar gains have delayed effects because of building thermal mass, there is significant benefit in predictive control and optimal operation of passive and active storage that utilizes real-time weather prediction (Athienitis, Stylianou, and Shou, 1990).

New building technologies, such as phase change materials (PCM), active façades with advanced daylighting devices, and building-integrated solar systems, open up new challenges and possibilities to improve comfort and reduce energy use and peak loads, and they need to be taken into account in developing optimal control strategies. The energy requirements and control needs of commercial and residential buildings are usually quite different. For example, in commercial buildings, cooling and lighting play major roles, while in houses, especially in cold climate regions, space heating and domestic hot water heating dominate energy consumption.

Plug loads (e.g., due to appliances and office equipment) represent a large portion of building energy consumption and their share is increasing, as HVAC and lighting systems become more energy efficient. Demand response strategies, such as scheduling of appliances, are becoming more popular as a way to significantly reduce the impact of plug loads on peak electric demand.

1.1.2 Design of Smart Net ZEBs and Modeling Issues

The design of smart net-zero energy buildings requires the following three key approaches:

An integrated approach to energy efficiency and passive design;

An integrated approach to building design and operation. Optimized net-zero energy buildings need to be designed based on anticipated operation so as to have a largely predictable and manageable impact on the grid. Smart buildings optimally linked with smart grids will enable a reduction in the need to build new power plants; and,

The concept of solar optimization requires optimal design of building form and orientation so as to provide the maximum capture of solar energy from near-equatorial facing façades and roofs for conversion to solar electricity, useful heat, and daylight.

To design a Net ZEB efficiently in an optimal manner, a rigorous quantitative approach is required in all stages of design starting from the conceptual phase. One of the unique challenges is how to handle the interaction and integration between the energy generating systems (such as building-integrated photovoltaic/thermal systems), the heating, cooling, and ventilating systems, and the building envelope in the different design stages. Model resolution and complexity is a key issue addressed in this book (Chapter 2) and gaps in simulation are also discussed, particularly in relation to four in-depth case studies (Chapter 7).

1.2 Scope of this Book

Chapter 2 discusses fundamental concepts, such as building thermal dynamics and different modeling approaches, design strategies (passive solar and energy efficiency measures), and technologies (renewable energy systems, heating and cooling technologies, and thermal storage) required to achieve net-zero energy in buildings. Because net-zero energy is an ambitious goal, the combination of systems and their integration is fundamentally important from the start of the design process to detailed design and building operation. This chapter discusses not only the individual technologies, but also effective integration strategies. It provides links to the application case studies that further exemplify the modeling techniques and technologies presented in the chapter.

Chapter 3 focuses on comfort considerations and models for different climates. Thermal comfort models are discussed, together with visual and acoustic comfort, as well as indoor air quality. Because of the highly efficient building envelopes in Net ZEBs, greater reliance on passive approaches, and a general trend toward higher glazing areas, comfort is particularly important for Net ZEBs. For example, in Net ZEBs with hybrid/natural ventilation systems there is a strong link between visual, thermal, and acoustic comfort.

Chapter 4 discusses different design processes and tools to support the design of Net ZEBs. Unlike other types of high-performance buildings, the net-zero energy target necessarily requires a high degree of accuracy in performance predictions, an integrated design process, and a combination of energy efficiency measures and renewable energy technologies. This chapter demonstrates the value of building performance simulation in design from conception to detailed design by providing accurate predictions for energy performance.

Chapter 5 presents different approaches, techniques, and considerations for Net ZEB optimization, including cost minimization and comfort. Examples from different countries, such as Finland and Italy, are presented.

Chapter 6 introduces matching of load with generation, grid interaction, and advanced control issues for Net ZEBs. Since the load profile of such buildings often peaks at different times from the generation peak, it is important to study this mismatch and how it can be addressed in order to optimize the interaction with electricity grids by shifting and reducing peak demand.

Chapter 7 provides detailed information about four diverse Net ZEBs (Figure 1.1), which are summarized in Table 1.2. These high-quality case studies were selected because they have at least one year of high-resolution measured data and the authors were intimately involved in all of them from conception to operation. The aim of this chapter is to draw lessons from the case studies, the design and simulation tools used and their gaps, and finally the technologies used and their integration. The last section of each of the case studies examines the redesign of archetype buildings based on additional information, new technologies, and lower material and component costs since they were built.

Fig. 1.1 The four Net ZEB case studies. Clockwise from top left: ÉcoTerra (Image courtesy of Agnieszka Koziol), Leaf House (Image courtesy of Loccioni Group), ENERPOS (Image courtesy of Jérôme Balleydier), and NREL RSF (Image courtesy of Dennis Schroeder, NREL)

Table 1.2 Summary of four in-depth case studies presented in Chapter 7

Case Study

Description

Location and Climate

ÉcoTerra House

Detailed monitored data available – partly designed by some of the authors; related scientific publications also by authors (Athienitis, O'Brien, Chen)

Canada's first near net-zero energy demonstration house. Completed in 2007, commissioned for 2 years, now occupied with feedback from occupants;200 m

2

rural detached house with building-integrated thermal/photovoltaic roof, ventilated concrete slab, passive solar optimized, and a ground source heat pump

Eastman, Quebec, CanadaCold, relatively sunny climate

Leaf House

Detailed monitored data available – engineers who participated in design provided input; related scientific publications also by authors (Cellura, Guarino, Cesarini)

6-unit low-rise multiunit residential building with passive solar features, both solar thermal and photovoltaic collectors, and a heat pump

Ancona, ItalyMediterranean climate – hot summers, mild-cold winters

National Renewable Energy Laboratory – Research Support Facility (RSF)

Detailed monitored data available – task participants work in the building; task meeting was held in the building; related scientific publications also by authors (Chen, Yip, Athienitis)

A large institutional building consisting of offices, laboratories, and a large server room. Energy features include good natural ventilation and advanced daylighting design using fixed louvers and high, reflective ceilings; radiant cooling, a large photovoltaic array; and a transpired solar collector to preheat fresh air

Golden, Colorado, USACold sunny – mountain climate

ENERPOS

Detailed monitored data available – task participants work in the building; related scientific publications also by authors (Lenoir, Kapsis, Garde)

A medium-sized energy-positive academic building with natural ventilation, daylighting, solar shading, and a large photovoltaic array

St-Pierre, Reunion Island, FranceTropical climate

Chapter 8 concludes with a discussion on challenges and future directions in the design of Net ZEBs.

This book was written primarily by Subtask B of the International Energy Agency Solar Heating and Cooling Program Task 40/Energy in Buildings and Communities Annex 52. Subtask B, titled Net ZEB Design Processes and Tools, was focused on studying modeling methodologies and design processes for the state-of-the-art Net ZEBs. Subtask B participants used carefully selected high-quality Net ZEB case studies to form a greater understanding of practical and technical challenges, including modeling considerations. Members of Subtask B were a diverse group of researchers and designers. Readers are encouraged to explore the products of five years of in-depth studies by the 50 IEA Task/Annex researchers world-wide on the Web site task40.iea-shc.org.

References

Athienitis, A.K. and Santamouris, M. (2002)

Thermal Analysis and Design of Passive Solar Buildings

, James & James, London.

Athienitis, A.K., Stylianou, M., and Shou, J. (1990) A methodology for building thermal dynamics studies and control applications.

ASHRAE Transactions

,

96

, 839–848.

International Solar Energy Society (ISES) (2001)

Solar Energy: State of the Art

, James & James, London, UK.

Marszal, A.J., Heiselberg, P., Bourrelle, J.S., Musall, E., Voss, K., Sartori, I., and Napolitano, A. (2011) Zero energy building – A review of definitions and calculation methodologies.

Energy and Buildings

,

43

, 971–979.

Voss, K. and Musall, E. (2011)

Net Zero Energy Buildings

, Detail Green Books – IEA SHC Task 40/EBC Annex 52, sponsored publication, Munich, Germany.

2Modeling and Design of Net ZEBs as Integrated Energy Systems

Andreas Athienitis, Maurizio Cellura, Yuxiang Chen, Véronique Delisle, Paul Bourdoukan, and Konstantinos Kapsis

2.1 Introduction

Net-zero energy buildings (Net ZEBs) are emerging as a quantifiable design concept and a promising solution to minimizing the environmental impact of buildings. This is the main concept that we will focus on in this chapter with emphasis on dynamic modeling and examples of technological approaches to achieve net-zero energy. Net ZEBs, which minimize energy consumption and optimally use incident solar radiation, both passively and actively, are usually defined as those that export as much energy as they import, over the course of a year (also known as net-zero site energy (Torcellini et al., 2006)). A review of international work on Net ZEBs was undertaken by the International Energy Agency Solar Heating and Cooling Program (IEA SHC) Task 40/Energy in Buildings and Communities (EBC) Annex 52 and its Subtask A studied several alternative definitions and calculation methodologies. Modeling, design, and optimization of such buildings have been studied by Subtask B (STB), which identified key issues that need to be addressed as follows:

– What is the appropriate model resolution for each stage of the design of Net ZEBs?

– What is the role of simple spreadsheet-based tools (e.g., RETScreen (NRCan, 2010) and PHPP (iPHA, 2013)) versus more advanced detailed simulation (such as ESP-r (ESRU, 2013) and EnergyPlus (EERE, 2013)) and optimization tools?

– What other tool capabilities are needed to model new technologies, such as building fabric-integrated phase-change materials (PCMs)?

A three-dimensional conceptual problem space has been developed (Figure 2.1) to represent the framework being used by STB to define the role of modeling in Net ZEB design. Different simulation tools include different technologies and simulate building fabric energy transfer with different levels of detail. They also utilize different techniques to model the transient response of buildings and their systems to changes in internal and external thermal loads.

Fig. 2.1 The 3D matrix representing model resolution, technologies, and design stage

Appropriate modeling of building-integrated solar energy systems (thermal, electric, hybrid, and daylighting) is essential for the design of Net ZEBs and the study of optimal control strategies. These systems will play a major role in achieving the net-zero energy goal and need to be carefully selected, modeled, and sized for an accurate design. At the early stage of design, a simplified software tool, such as RETScreen, may provide enough accuracy to size a building-integrated photovoltaic (BIPV) or a solar thermal system as it provides monthly estimates of energy generated. However, a BIPV/thermal system (BIPV/T) that generates both electricity and heat requires estimation of the heat recovered and how it can potentially be used – to heat ventilation air, to heat water, or space heating (directly or through a heat pump). To properly simulate these systems, there is a need for tools characterized by a high integrity representation of the dynamic and connected processes.

It is also recognized that the optimal interaction between a Net ZEB and a smart grid can facilitate reductions in peak electricity demand and under conditions of high photovoltaic (PV) penetration rates in neighborhoods, the use of energy storage in the building can reduce the peak renewable electricity supplied to the grid.

Figure 2.2a shows a typical demand and generation profile for a Canadian net-zero energy house on a cold sunny day. As can be seen in the figure, there is a high demand (negative) for heating in the early morning, so that if the weather of the previous day was similar, building-integrated thermal mass could be used to reduce this peak through collected solar gains. The net-zero energy balance may be achieved through a combination of passive and active solar technologies, heat pumps, combined heat and power (possibly using biofuels/biomass), and energy efficiency measures to reduce energy consumption for lighting and appliances as shown in Figure 2.2b. A plug-in hybrid electric vehicle (PHEV) may possibly be used as an electricity storage/backup device.

Fig. 2.2 (a) Schematic of demand and generation profile for a Canadian net-zero energy house (cold sunny day); (b) Net-zero energy solar home concept (Illustration: Samson Yip)

2.1.1 Passive Design, Energy Efficiency, Thermal Dynamics, and Comfort

There are two principal categories of building solar heating and cooling systems: passive and active. Passive systems integrate into the structure of the building technologies that admit, absorb, store, and release solar energy, thereby reducing the need for electricity use to transport fluids. In contrast, active systems include fans and pumps controlled to move air and heat transfer fluids respectively for space heating and/or cooling and domestic hot water (DHW) heating.

Current international trends in net-zero energy building design are expected to continue and will increasingly rely on a combination of active and passive solar systems as enabling technologies for net-zero energy solar buildings – solar buildings that produce as much energy as they consume over a year. Similarly, hybrid systems – active/passive and thermal/electric – will gain popularity, such as the photovoltaic/thermal systems that are described later in this document.

This section presents approaches that are primarily used for modeling and simulating passive solar systems and some building-integrated solar systems.

Passive solar technologies generally do not use fans or pumps in the collection and usage of solar heat. Instead, these technologies use the natural modes of heat transfer to distribute solar gains among different spaces. When applied to buildings, this generally refers to passive energy flows among rooms and envelope, such as the redistribution of absorbed direct solar gains or night cooling. Buildings that primarily use these technologies to reduce heating and/or cooling energy consumption are commonly described as “passive solar buildings.”1) The major driving forces for thermal energy transfer within a passive solar building are longwave thermal radiation exchanges and natural convection.

Passive technologies are integrated within the building and may include the following:

Near-equatorial-facing windows

with high solar transmittance and high thermal resistance. These properties maximize the amount of direct solar gains into the living space, while reducing envelope heat losses and gains in the heating and cooling seasons, respectively. Skylights are often employed for daylighting in office buildings and in sunspaces-solaria.

Building-integrated thermal energy storage

. Thermal energy storage, which is commonly referred to as thermal mass, may consist of sensible heat storage materials, such as concrete or brick, or PCMs. Two design options are

isolated thermal storage

(not directly thermally coupled to the living space) or solarium/sunspace and

collector-storage walls

. A

collector-storage wall

– known as a Trombe wall – consists of thermal mass that is placed directly in front of the glazing; however, this system has not gained much acceptance since it limits the views to the outdoor environment. Direct gain systems are the most common implementation of thermal storage because of their simultaneous benefits for providing passive heating, daylight, and views to the exterior.

Airtight insulated opaque envelope

. Such an envelope reduces heat transfer to/from the outdoor environment, but must be chosen to be appropriate for the local climate. In most climates, this energy efficiency aspect is an essential part of the passive design. A solar technology that may be employed in conjunction with opaque envelopes is transparent insulation combined with thermal mass to store solar gains in a wall to turn it into an energy positive thermal element. In addition to optimized thermal response, the envelope should control air and moisture transfer between the indoor and outdoor environments.

Daylighting technologies and advanced solar control systems

. These technologies provide passive daylight transmission. They include electrochromic and thermochromic coatings, motorized shading (internal and external) that may be automatically controlled, and fixed shading devices, particularly for daylighting applications in the workplace. Newer technologies, such as transparent photovoltaics, can also generate electricity while transmitting daylight. Such technologies introduce a new level of complexity in building design since they generate electricity, have direct and indirect impacts on cooling loads, as well as electricity consumption for lighting (reducing the need for electric lighting through daylight). During the cooling season the need to provide daylight, while preventing excessive solar gains that raise cooling loads, should be carefully considered.

Building-integrated photovoltaics

. Photovoltaic panels can serve as exterior cladding or roof shingles while producing electricity with no moving parts. Thus, they can be considered a passive element. In some cases, active heat recovery from BIPV through closed loop (e.g., water pipes as in solar collector absorber plates) or open loop (flowing air in a cavity behind the PV panels) can also be used to produce useful heat; these BIPV/T systems are hybrid building elements.

Simulation and analysis of the thermal and energy fluxes in a building facilitate the choice of materials and subsystems for the local climatic characteristics and building function. Many thermal processes are relevant in the assessment of building thermal behavior, such as

– heat conduction through exterior walls, roofs, ceilings, floors, and interior partitions;

– solar radiation through transparent surfaces;

– latent or sensible heat generated in the space by occupants, lights, and appliances;

– heat transfer through ventilation and infiltration of outdoor air and other miscellaneous heat gains (ASHRAE, 2009a).

One of the most important of these thermal processes is thermal conduction through a multilayered wall that is calculated in several ways, such as

– Finite difference methods

– Finite element methods

– Transform methods (frequency domain and time domain), including time series methods (such as those using

z

-transfer functions described below and used in

Chapter 6

).

During the thermal analysis of a building, it is necessary to determine heating loads and room temperature fluctuations either for design days or with given typical annual weather data. For sizing equipment and components, it is desirable to evaluate the building response under extreme weather conditions for many design options, each time changing only a few of the building parameters, until an optimum or acceptable response is obtained. For a solar building that includes direct gain as a major solar energy utilization mechanism, it is also useful to study the free (passive) response of the building as this enables the designer to determine the relation between room temperature fluctuation and storage of passive solar gains. This relationship is an important consideration for thermal comfort studies, for which room temperature swings outside the comfort range are to be minimized. Thermal comfort is further discussed in Chapter 3.

There are two main steps in creating a mathematical model that describes the energy transfer processes in a building. First, the thermal exchanges must be modeled as accurately as is necessary; while an acceptable level of precision is desired, too much complexity can limit the model usefulness in analysis and design. Second, an appropriate method of solution must be chosen to determine the room temperature and auxiliary energy loads. The type of solution may be numerical or analytical, as long as the variables of interest can be determined. As an optional third step, a method of analyzing the system without simulation can be developed; this is particularly important for comparison of design options on a relative basis, for optimal control studies and peak electricity demand reduction (see Chapter 6).

The degree of detail and model resolution required during the energy and thermal analysis of a building depends on the design stage. For the early stages of design, when the geometry of the building surfaces is not fully fixed, a steady-state or an approximate dynamic model is often adequate. However, more detail is required for a preliminary design, taking into account all objectives of building thermal design and the specific characteristics of the HVAC and solar systems considered.

Modeling the longwave radiant heat exchanges of the zone interior is more important with direct gain systems compared to indirect gain systems and generally requires more modeling detail, particularly if a floor heating system is integrated. In designing solar buildings, a key objective is to store energy in the walls during the daytime for release at night without having uncomfortable temperature swings. If PCMs are integrated in the room interior layers the room mean radiant temperature variation is expected to be reduced.

A basic characteristic of a passive solar building is the strong convective and conductive coupling between adjacent thermal zones. This coupling is very important between equatorial-facing rooms receiving a significant amount of solar radiation transmitted through large windows and adjacent rooms that receive very little solar radiation. For example, heat transfer by natural convection through a doorway connecting a warm direct gain room or a solarium and a cool north facing room, can be an effective way of heating the cool room. The transfer of heat can be controlled so as to avoid backflow to the solarium at night by having motorized inlets that close.

Periodic conditions are usually assumed (explicitly or implicitly) in dynamic building thermal analysis and load calculations. Heating or cooling load, that is, the auxiliary heat energy input/removal required to maintain comfort conditions, is usually calculated for a design day. The peak heating load is used to size heating equipment and the peak cooling load is used to size cooling equipment.

The following three types of approximations are commonly introduced in mathematical and physical models to facilitate the characterization of the building thermal behavior:

Linearization of heat transfer

. Convective and radiative heat transfer are inherently nonlinear processes and the respective heat transfer coefficients are usually linearized so that the system energy balance equations can be solved by direct linear algebra techniques and possibly represented by a linear thermal network. Linearization generally introduces less error for longwave radiant exchanges between surfaces than convection between room surfaces and room air.

2)

In some cases heat flow reversal can occur, such as between a cold floor and warm air, where the convective heat transfer coefficient can be of the order of 1 W/m

2

K compared to 3 W/m

2

K for a heated floor and cold air.

Spatial and/or temporal discretization

. Transient heat conduction is described by a parabolic, diffusion type partial differential equation. Thus, when using finite difference methods, a conducting medium with significant thermal capacity, such as concrete or brick, must be discretized into a number of regions, commonly known as control volumes, which may be modeled by lumped network elements (thermal resistances and capacitances). Also, time domain discretization is required with an appropriate time step employed. In response factor methods only time discretization is necessary. For frequency domain analysis none of these approximations are required; in periodic models however, the number of harmonics employed must be kept within reasonable limits. It should be noted that when thermal storage undergoes phase change (e.g., PCMs) a linear approximation may not be possible in some cases and specialized modeling is required.

Approximations for reduction in model complexity – establishing appropriate model resolution

. These approximations are employed in order to reduce both the number of simultaneous equations to be solved and the required data input or to enable the derivation of closed form analytical solutions. They are by far the most important approximations. Examples include combining radiative and convective heat transfer coefficients (so-called film coefficients commonly employed in building energy analysis), assuming that many surfaces are at the same temperature, or considering certain heat exchanges as negligible. Such approximations need to be carefully selected and applied by taking into consideration the expected temperature variations (spatial and temporal) in a zone. For example, a zone with large windows and floor heating may exhibit large spatial temperature variations, in which case the use of combined film coefficients would result in high errors in room operative temperature and floor heating rate calculations.

A major part of the modeling process considers transient heat conduction in the building envelope. In most cases relating to heating or cooling load estimations, energy savings calculations, and thermal comfort analysis, it is generally accepted that one-dimensional heat conduction may be assumed. Thermal bridges, such as those present around corners and at the structure, are generally accounted for in calculating the effective thermal resistance of building envelope elements by using a more detailed spatial model or simplified techniques, such as the parallel heat flow path method. However, the thermal storage process may usually be adequately modeled as one-dimensional for well-insulated buildings. For steady state calculation of thermal bridge effects, a 2D or 3D calculation of thermal conductance is sometimes desirable (e.g., parallel heat flow method (ASHRAE, 2009a)).

Direct gain zone modeling (i.e., a zone with high interior solar gains) includes certain important requirements in addition to those required for traditional building modeling. In particular, there is an increased need to address thermal comfort requirements and to allow the room temperature to fluctuate so as to enable storage of direct solar gains in building integrated exposed thermal mass. In addition, for an office environment, daylighting considerations will dominate, such as the need to uniformly distribute daylight and to prevent glare.

Peak heating/cooling load calculations are a major aspect of heating/cooling equipment sizing and need to take into account building thermal storage capacity and dynamic variation of both solar radiation and outdoor temperature, in order to avoid over-sizing of HVAC systems. For most mild temperate climates, a heat pump will provide an efficient auxiliary heating and cooling system. Well-insulated buildings with effective shading systems and natural ventilation have a reduced need for auxiliary cooling. Similarly, appropriate sizing of the near-equatorial facing fenestration systems will satisfy most heating requirements on sunny days.

Frequency domain analysis techniques with complex variables may be employed for steady periodic analysis of multilayered walls and zones. They provide a convenient means for periodic analysis, in which parameters, such as magnitude and phase angle of room temperatures, and heat flows are obtained. The well-known cooling load temperature differential (CLTD) method proposed for many years by ASHRAE (McQuiston, Parker, and Spitler, 2005) for cooling load calculations is essentially an admittance-based technique, with magnitudes and phase lags of important frequency domain transfer functions. In the United Kingdom, an admittance-based technique is used to calculate room temperature swings and time lags between cause (e.g., sol-air temperature peak) and effect (peak of room temperature rise).3)

2.1.2 Detailed Frequency Domain Wall Model and Transfer Functions

Building heat exchanges may be represented by a thermal network, and transfer functions are obtained by performing an energy balance at all nodes in the Laplace domain. Both lumped and distributed elements can be considered using this approach. Simple models that do not represent in detail infrared radiation heat exchanges between room interior surfaces can usually be solved analytically. Transient heat conduction (assumed to be one-dimensional) in walls can be accurately represented without discretization using the approach that follows.

2.1.2.1 Distributed Parameter Model for Multilayered Wall

Consider a slab and assume one-dimensional transient conduction with uniform properties k, ρ, c. We have

(2.1)

where α = k/(ρc) is the thermal diffusivity

The boundary conditions will include convective heat transfer, absorbed solar radiation (a heat source), and longwave radiation exchange with other surfaces.

After taking the Laplace transform of Eq. (2.1) and some algebra, the equations for the conditions at the two surfaces may be expressed in the so-called cascade equation matrix form (Beccali et al., 2005b) as follows (assuming heat flux q is positive into the wall on both sides):

(2.1a)

The parameter k is the thermal conductivity, L is thickness, γ is equal to (s/α)1/2 and s is the Laplace transform variable. For frequency domain analysis, including admittance calculations, s is set equal to jω (s = jω) where j = √−1 and ω = 2π/P. For diurnal analysis, the period P = 86,400 s. For a multilayered wall we can multiply the cascade matrices for each successive layer to get an equivalent wall cascade matrix that relates conditions at one surface of the wall to those at the other surface, thus eliminating all intermediate nodes with no approximation required and no discretization:

(2.1b)