White Paper
BACnet and EnOcean enable Energy Efficient Buildings
Integration of batteryless wireless sensors offers amazingly newopportunities for BACnet building automation
When it comes to choosing a facility’s backbone for carrying buildingautomation information, wired BACnet bus systems have become a norm.
However, wireless systems have been growing in popularity since the arrivalof energy-autonomous and service free wireless components based on
EnOcean technology. Practical experience shows that the two technologies,
side-by-side, exhibit advantages that maintain an ideal wired/wirelessbalance—combining the strengths of both.
By Marc Dugré (Regulvar Inc.), Fabian Freyer (Thermokon SensortechnikGmbH) and Armin Anders (EnOcean Alliance)

1. Wired and Wireless compared
The following collective assessment of major criteria relevant for the market
indicates that neither of the two transmission media, Wired or Wireless, comesout alone on top in a building-automation scenario. For an optimal solution, it
takes both; each implemented where it is better than the other.

Features
Range
Installation effort and flexibility
Data volume
Availability of information in room
Reliability
Cost

Wired
++
-++
++
+

Wireless
++
-++
+
++

Table 1: Features of wired and wireless transmission media

1.1 Range
If you want to transmit data over long stretches in a building (more than 30
meters, for instance) there is no economical alternative to a wired bus. An
obvious example is the transmission of sensor and actuator information
across many floors from a central point. For communication between
buildings, long distances, and for very large amounts of data, fiber optic
networks are a good option. But signal transmission within the same floor, ina radius up to about 30 meters, is easily handled by the right wirelesstechnology.

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In addition to the unique energy harvesting maintenance free wirelesssolutions from EnOcean, another significant differentiator that sets EnOcean
above other potential wireless choices is the use of sub-gigahertz frequencies:
868 MHz in Europe and the Middle East, and 315 MHz in the USA and the Far
East. These frequencies are in contrast to wireless systems like those based
upon 802.15.4 RF radios, ZigBee and Bluetooth, nestled in the 2.4 GHz band.
The lower, more optimal frequencies exhibit lower attenuation through walls
and achieve about twice the range for the same transmitting power.

Fig. 1: Transmission loss vs. frequency

Figure 2 illustrates the performance of wireless systems in buildings as afunction of their frequency. Frequencies below 250 MHz are unfavorable
because of the inefficiency of their antennas, if these are to be made compact
enough to match market requirements. On the opposite end, frequencies of
1 GHz and higher suffer increasingly from propagation loss through walls andother obstacles. The ideal range is found between around 300 MHz and 1 GHz,
where you find low attenuation and the range needed to make a systemeconomical; i.e., fewer devices per square meter.
1.2 Installation effort and flexibility
When it comes to installation effort, building alterations and subsequent
wishes for expansion, the advantages are clearly on the side of wirelesstechnology. Wireless components can be easily fitted, for little cost, even on
surfaces inaccessible for wired solutions. Speed and flexibility are advantages
not only when expanding and altering at a later date but also during initialplanning and final installation; where components’ placement can be changed
at the last minute—a relatively common occurrence in building operations.
1.3 Data volume
Battery-less and service free wireless sensors are ideal for sending measured
data packets and control commands, which in most cases are of small data
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volume. These data packets can then be funnelled back to monitoring stations
or shared with other devices in different locations via a wired infrastructure,
where higher bandwidths are available, where fully isolating routing can beachieved, and where fewer government restrictions are imposed.
1.4 Availability of information
A benefit of using wireless is that the information sent by devices is accessible
anywhere in a room or space, not just along the wires. So components can be
optimally positioned without concern for existing wires or inaccessibility ofplaces for wiring. Combining a wired BACnet system with EnOcean wirelesscomponents allows an installation to benefit from both technologies.

Fig. 2: Window contact

Fig. 3: Bidirectional wireless room sensor

1.5 Reliability
The reliability of wired BACnet bus systems has been widely proven. However,when it comes to wireless systems, some people are still sceptical, but many
feel increasingly confident since the advent of EnOcean wireless. After all,there are already over 100,000 buildings benefiting from the advantages of
EnOcean wireless technology. Installations include corporate headquarters(e.g. SAP, IBM, Bosch, Siemens, Nestlé), public buildings (schools, hospitals,
government facilities), historical buildings, residences, landmarks, retails,
industrial and hotels.

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EnOcean nodes avoid the 2.4 GHz band of Bluetooth and WLAN. Devices inthat range have to share a limited number of channels. The more popular thisband becomes (the more WLAN-enabled PCs are available), the greater the
problems will become through interference with networks and otherpermanently active systems, such as mobile phones, Bluetooth, and cordlessvideo monitors. Well-founded radio planning is the next building block in thereliability of wireless systems. Here, EnOcean offers professional support of
instrumentation tailored to that purpose, as well as planning guidelines longtime proven in practice.
How wireless components obtain their energy is a further and major aspect of
secure, reliable installation: Reduced range, rather than failure of sensing, isthe result of batteries running out of power, which results in having to replacebatteries to keep the system functioning as a whole. In the EnOcean
technology, the focus is “no batteries; so, no maintenance.” The use of freely
available, ambient energy - generated by sunlight, motion, heat, or vibration,for instance - is a key benefit of the wide market acceptance of this wirelesssolution, especially in buildings.
The concerns of building professionals regarding battery-powered wirelesssensors are quite justified when you think of the thousands of batteries in amodern building that would need regular replacement. These concerns do not
apply to EnOcean sensors. Moreover, data published about the expected,
average lifetime of batteries can seldom be taken at face value. Although theuse of batteries may initially be more cost-attractive, the service, disposal(toxic waste), and malfunctions can quickly negate the initial savings.
1.6 Cost
Today’s wireless systems already offer cost benefits of as much as 15% upon
first-time installations (depending on complexity) compared to some wired
solutions with the same range of functions. When alterations or expansions
are undertaken (statistics show that the average office building is reconfigured
about every five years), the cost benefit can go up to 80%.
Tying the EnOcean systems into the BACnet network allows those benefits toincrease by extending the physical reach of the data they share.

2. Standards
2.1 The BACnet Standard
BACnet is a manufacturer-independent data communication protocol for
Building Automation and Control Networks. Developed under the auspices of
the American Society of Heating, Refrigerating and Air-Conditioning Engineers(ASHRAE), BACnet is an American national standard, a European standard, aWhite Paper – BACnet & EnOcean

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national standard in more than 30 countries, and an ISO global standard. The
protocol is supported and maintained by ASHRAE Standing Standard Project
Committee 135.
2.2 The EnOcean Standard
The EnOcean Alliance is a consortium of companies working together tofurther develop and promote self-powered wireless monitoring and control
systems for sustainable buildings by formalizing and opening the interoperable
wireless standard. The EnOcean Alliance has developed the specification for
the interoperability of the sensor profiles for the wireless products operating inlicense free frequency bands and is currently applying for ratification as aninternational standard at the IEC technical committee JTC 1/SC 25/WG 1. The
EnOcean Alliance is open to anyone and is a manufacturer-independent nonprofit organization based in San Ramon, CA.

3. Putting BACnet and EnOcean together
The joint objective of the BACnet Organization and the EnOcean Alliance is:simple but substantial reduction of the energy requirement in buildings. The
two technologies match optimally for this purpose: BACnet is the leading wired
technology for intelligent building-services management; while the EnOcean
standard represents wireless-based automation technology.
For example, self-powered sensors and actuators communicate wirelessly as
an intelligent sub-network in a room or area; doing away with conventional
cabling precisely where the configuration of the room is most-frequently
altered. This also obviates the need for those associated costs.
Communication with the control or supervision level can then travel through
BACnet gateways, each linking many rooms or intelligent sub-networks to the
BACnet backbone of building automation. In this way, the flexibility of awireless system is ideally combined with the large bandwidth and range of awired backbone.
The rooms in modern office buildings are rearranged, on average, about every
five years; so wireless systems provide just the right flexibility. More andmore, interior architects are discovering the new possibilities of design andinstallation presented by wireless systems, where a switch or sensor is locatedno longer by where electric wires are located. They can be put in the bestplace, in ergonomic terms. Switches to control lighting and blinds can be
attached simply to each workplace of an open-plan office, for example. Lightswitches can be adhered to the headboard of a hotel bed, to a mirror, thetiles, or near the shower partition in the bathroom.
Room temperature sensors no longer need to be installed near doors, avoiding
corruption of the temperature reading by the opening and closing of a door.
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Products enabled by EnOcean reduce the laying of cables inside and outsidebuildings, allowing the user to place sensors just about anywhere (e.g., onglass, furniture, windows, and ceilings).

4. BACnet interoperability
BACnet ensures interoperability between devices of different manufacturers if
all participants in a project agree on certain BACnet interoperability building
blocks (BIBBs) defined by the standard. A BIBB defines the services andprocedures that have to be supported at the server and client end to
implement a particular system requirement. The protocol implementation
conformance statement (PICS) accompanying a device lists all supported
BIBBs, object types, character sets and options in communication.

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5. EnOcean Interoperability
To save transmission energy the EnOcean radio telegrams must be designed
to be as short as possible. Because of that, the sensor informs his receiverduring the teach-in only about his function and data decoding characteristics.
For this purpose the so called “EnOcean Equipment Profile” (EEP) has been
agreed within the EnOcean Alliance, a telegram profile number that relates toa look up interpretation table in the receiver.
To enable interoperability of equipment from different manufacturers astandard was defined for the teach-in procedure, for the data communicationand for the EEP itself. Up to now the specification was restricted tounidirectional sensor communication (around 50 EEPs), those are currently
enhanced to bi-directional sensor communication and bid-directional
communication of a gateway with EnOcean wireless actuators.
Byte#

Description

SYNC_BYTE 0

Synchronization Byte (0xA5)

SYNC_BYTE 0

Synchronization Byte (0x5A)

TYPE

Telegram info, e.g. length, Rx/Tx

ORG

Telegram info, e.g. PTM/STM

DB_3

Data byte 3

DB_2

Data byte 2

DB_1

Data byte 1

DB_0

Data byte 0

ID_3

Byte 3 of transmitter ID

ID_2

Byte 2 of transmitter ID

ID_1

Byte 1 of transmitter ID

ID_0

Byte 0 of transmitter ID

STATUS

Status info, e.g. repeater level

CHK

Checksum (LSB)

Table 2: Serial data protocol of an EnOcean radio receiver

1. Press LRN
pushbutton
Sensor
2. LRN telegramm will be send
ORG

ID

8 Bit

32 Bit

ORG
Value

FunctionType

SensorID

EnOcean Equipment Profile (EEP)

Figure 4: Serial data protocol during tech-in (EEP equipment profile)

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6. BACnet/EnOcean Gateway
Today twisted pair is the most important media for BACnet products. This
enables a high quality of data transmission and the possibility to supply power
to the connected units. Using a gateway is a very simple and already existing
solution to combine the power of both worlds: Wired BACnet and WirelessEnOcean. In the following the functions of a BACnet MS/TP RS485 EnOcean
wireless receiver is described. Visit www.big-eu.org for further information anddefinitions on the subject of BACnet.
6.1 Device description
Devices can be connected by a twisted-pair cable (120 Ω line resistance). The
maximum number of bus users (without use of a bus repeater) is given by the
RS485 transceiver. The protocol used is the international standard BACnet
MS/TP. This enables connection to appropriate remote terminals such as an
automation station or a building services management system supporting the
BACnet MS/TP protocol.
The standard defines the transmission parameters as 8N1, i.e. 8 data bits, noparity, 1 stop bit. The baud rate is freely selectable (9600, 19200, 38400,
57600, 76800, 115200), and is set by DIP switches. It is also possible to set
the BACnet MAC address (bus address) of the device. A different bus address
is needed for each device.
6.2 Configuration tools
BACnet MS/TP wireless receivers are always operated together with other
BACnet automation stations or building services management systems such as
BACnet operating workstations. All parameter settings are possible throughthe BACnet network. Tools from the particular manufacturer of an automation
station or building services management system are used to start up a BACnet
network.
6.3 BACnet interoperability building blocks
The standard defines interoperability building blocks (BIBBs) enabling BACnet
devices to operate together. The different devices can be allocated to these
BIBBs, which use different services to communicate with one another. A
distinction is made between data and requests:
A
B
DS

ClientServerData sharing

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DM
RP
COV

Device management
Read property
Change of value

The following BIBBs are implemented:
DS-RP-B
DS-WP-B
DS-COVU-B
DS-WPM-B

Read property
Write property
Send data on change of value
Write multiple properties

DM-DDB-B
DM-DOB-B
DM-DCC-B

Device properties
Address information about objects
Communication control

6.4 BACnet device profile
BACnet defines various profiles that offer and support different services. Oneof these ready defined types should be used for good interoperability.
The EnOcean BACnet gateway operates with a device profile called BACnet
application-specific controller (B-ASC).
6.5 BACnet objects
The gateway has various BACnet objects. Four of these objects serve for thebasic setting of the device. The others describe the slots, each interpreting awireless receiver. A slot is described by 12 objects (six analog inputs, fourbinary inputs, one binary value, one multistate input).
6.5.1 Objects for basic setting of device
Object nameOffset device ID

Object type /instance
Device / 100(default) + MAC
address of address
switches
Analog value 1

EnOcean teach-inAnalog value 2

Thermokon_SRC_BACnet

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Meaning
Basic settings of thedevice, e.g. MAX master.
This value plus the set
MAC (0-127) corresponds
to the device ID(writeable 0-4194200)
after write, reset andnew initialize.
The set value selects the9/ 16

COV mode

Multistate value 1

next slot to be teachedin, after which it isautomatically reset to 0.
This setting is for COV
mode. The following
modes are supported:- Off- Local broadcast- Global broadcast

6.5.2 Objects in each slot in not teached-in state
The instance numbers of a slot always start on round hundreds, e.g. slot 1 on
100, slot 2 on 200, through slot 32 on 3200.
Object nameSensor01_DataByte_0

Object type /instance
Analog input 100

Sensor01_DataByte_1

Analog input 101

Sensor01_DataByte_2

Analog input 102

Sensor01_DataByte_3

Analog input 103

Sensor01_Org_Byte

Analog input 110

Sensor01_Receive_Time

Analog input 111

Sensor01_Bi1

Binary input 100

Sensor01_Bi2

Binary input 101

Sensor01_Bi3

Binary input 102

Sensor01_Bi4

Binary input 103

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Meaning
Interpreted data of
EnOcean data byte 0 withanalog information.
Interpreted data of
EnOcean data byte 1 withanalog information.
Interpreted data of
EnOcean data byte 2 withanalog information.
Interpreted data of
EnOcean data byte 3 withanalog information.
Mapping of EnOcean ORG
byte.
Time since last received
wireless telegram, COV
time for "Sensor Overdue".
Interpreted data of
EnOcean data byte 0 withdigital information.
Interpreted data of
EnOcean data byte 0 withdigital information.
Interpreted data of
EnOcean data byte 0 withdigital information.
Interpreted data of
EnOcean data byte 0 withdigital information.
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Sensor01_ClearSlot

Binary value 100

Sensor01_Mi0

Multistate input
100

The present value must be
set to 1 to clear the sensor
teached into the slot.
Interpreted data of
EnOcean data byte 0 withmultiple states/information.

6.5.3 Description of further BACnet properties
6.5.3.1

Device object -> MAX master property

This property can be written between 0 and 127, and defines up to what
address further users are polled on the bus. It is an MS/TP-specific property.
6.5.3.2

Device object -> object identifier

Each device in a BACnet network requires a unique device ID. The device
offers two ways of altering the ID. The device ID is composed of the MAC
address, produced by the address DIP switch, and a device ID offset, written
by a BACnet object. The default as supplied for this object is 100. Device
identifiers from 0 through 4194299 can be set by altering the device address
or offset, after which the device is newly started and initialized.
6.5.3.3

Device object -> device name, description

These two properties are writeable, with a maximum text length of 128
characters. The object name property must also be unique within a BACnet
network.
6.5.3.4

Sensorxx_Org_Byte object

This shows, in addition to the ORG byte of the teached-in sensor (in thepresent value), its EnOcean ID and the EnOcean profile and type of thetransmitter. The ID, profile and type are contained in the appropriate property
description.
6.6

Functional description

6.6.1 Teach in wireless sensor
To teach in a wireless sensor, the number of the required slot must be enteredin the present value property of the EnOcean teach-in object. The nexttransmitter to send a teach-in telegram is teached in. After teach-in thepresent value is reset to 0. Teach-in is only possible to an unassigned slot.

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6.6.2 Clear slot
Each slot is allocated a ClearSlot object. If the present value is set to 1, thepreviously stored information is rejected, and a new wireless sensor can beteached into the slot.
6.6.3 Receive time
Each slot is allocated a Sensorxx_Receive_Time object that detects the timesince the last received wireless telegram of the teached-in transmitter. The
time shown in the present value is incremented by the second and reset to 0
when a telegram is received.
The value in the COV increment property writes the transmit cycle of a COV
message for this object. A telegram is generated if the time has elapsed andthe sensor is overdue. As supplied the COV increment is 65535, which
prevents sending COV messages. Times from 30 to 65535 seconds can be set.
6.6.4 COV procedure
The functionality can be selected with the multistate value object. Writing thepresent value property (1-3) selects the COV mode. When COV is active, thedata byte objects of a slot that are used (four) are transmitted after a wirelesstelegram is received. When the time in the Receive_Time object has elapsed,this object is also transmitted as a COV.

7. Best Practice of BACnet plus EnOcean
7.1 Energy saved through energy efficiency
About 40% of the energy needs of industrial nations are consumed inbuildings - where the potential for savings is quite enormous. How often haveyou driven past an office block late in the evening where all the lights are on,
but only a handful of people can be seen still working? How often have youentered an empty room where the heating or air-conditioning has been goingfull-blast for hours? The necessity to save energy is not only driven by its cost.
It is especially due to the prediction that many nations will simply not haveenough energy in the future to satisfy their needs.
Energy savings, therefore, increasingly becomes a challenge. Costly schemes
governed by demand for those regions highly affected are merely a short-term
necessity. The most effective solution is to construct new buildings, or alterolder ones, to make them energy-efficient. In a typical reconstruction case, it
is possible to save more than 30% of the building’s energy consumption.

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7.2 School renovated – 20% less installation cost and 30% energy
saved
There are various reasons for renovating a building. Of course, a major reason
is cutting the high cost of energy, which explains why an increasing number ofbuilders as well as owners and property managing companies have started
thinking about renovation. Older buildings in particular are often veritableenergy guzzlers because they have little or inadequate insulation. Renovatinga building with the objective of improving energy efficiency inevitably saves
money in the long term. The important thing is to select the right system. At
St. Joseph elementary school in Lacolle, Quebec (Canada), the decision
makers opted for EnOcean technology for the room temperature sensing
devices.
Saving Potential optimally tapped
Before its renovation, St. Joseph elementary school had no individual
temperature regulation system but what could be called a dual-zone regulation
for the entire school. As a result, it was often too cold in one half of the school
and too warm in the other -- depending on the intensity of sunshine. This alsomeant that the school‘s energy consumption was very high. To cut the energy
needed by heating and air-conditioning, and for extra comfort, the school
decided in summer 2008 to install a system based on self-powered wirelesstechnology from EnOcean. Sensors were put in place in 28 rooms, using lightas their natural energy source and requiring neither batteries nor any external
power supply. All room sensors are linked to a central BACnet system,
controlling the temperature in individual rooms. The project was implemented
by Regulvar, which served the school as consultant for the entire duration
Convincing Arguments
The main argument in clear favor of the EnOcean-enabled products was, inaddition to speedy integration and simple planning, the attractive pricecompared to cabled solutions. The room sensors have enabled the school toenhance comfort and substantially reduce its energy needs. Plus, the new
system implemented now allows metering and remote monitoring of energy
consumption via internet, e.g. on behalf of the education authority. A further
key argument was that the entire installation could be carried out without
interrupting the normal running of the school. Something that is out of thequestion with a cabled solution due to the need to break open the walls forlaying ducts needed to route the cabling.
Speedy and simple implementation
Installation of the whole system took just one week during October 2008 -including installation of the central control system for the monitoring andgovernment of energy consumption. As everything had to be in place andoperational before winter sets in, the simplicity and speed of installation was ahuge bonus for the school. As it turned out, the biggest challenge was finding
the right positioning of the room sensors because the school has thick walls ofWhite Paper – BACnet & EnOcean

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concrete and steel – normally a big challenge for wireless systems but noproblem for the EnOcean devices.
A good invest
Choosing EnOcean’s self-powered wireless technology saved the St. Joseph
elementary school 20 percent in installation costs alone. The cost of
implementing this wireless solution was 6000 Canadian dollars lower than for
a comparable – but disruptive -– cabled installation. Together with thesignificant energy savings, the school expects a return on investment within
two years. “To start with I admit that we were a little skeptical about this newtechnology”, says Christine Halpin, Principal of St. Joseph elementary school.
“But now we‘re very glad we chose it. We have more comfort, and we‘ve cut
our energy costs by a good 30 percent.”

Fig. 5: Renovation undertaken at anelementary school in Canada enabled it to
cut energy costs by some 30 percent

Fig. 6: Individual temperature
regulation uses light as its naturalenergy source

Fig. 7: The new system now allows
metering and monitoring of energy
consumption

Fig. 8: Visualization of room
temperature sensors

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8. Outlook
Future, second-generation interfaces will allow entirely bidirectional
communication: Data generated by EnOcean sensors can be retrieved directly
by BACnet actuators and controllers. BACnet controllers can in turncommunicate with EnOcean actuators.
Typical applications are those revolving around energy savings, such as
dimming or turning-off the lights when a room is empty; HVAC halting whenwindows are open; or standby mode of heating, ventilating, and airconditioning when a room is not being used.
EnOcean technology has become a standard among architects and system
integrators all over Europe, and is now well set to satisfy big markets in North
America and the Near East. Unlike meshed wireless networks, the wirelessswitches are not active and do not transmit all the time—only when actuated.
Interestingly, the electromagnetic emission of an EnOcean switch is much lessthan that of a comparable, conventional switch for a 100 W bulb. Initial
medical concerns about the high-frequency radiation from wireless sensors
were satisfied by scientific experiments. The use of EnOcean switches can thus
be recommended, without concern, in hospitals, schools, kindergartens, andgovernment and office buildings. Likewise, there are no environmental or
biological concerns regarding attaching such a wireless switch directly to theheadboard of a bed or to a bedside table.
About Regulvar Inc.
For over three decades, Regulvar has been setting the standard for excellencein automatic controls (HVAC) in Canada. Today, its open architecture platform
also integrates critical systems like access controls, video surveillance andlighting control for a wide range of commercial and institutional applications.
With over 400 employees, Régulvar is the largest building integrator in
Canada. Its head office is located in Montreal, but it provides services to all ofeastern Canada through twelve branch offices. Régulvar has successfully
installed thousands of BACnet systems, using mainly Delta controls. The
strength of its research and development team made it possible for Régulvar
to develop many gateways enabling communication between BACnet andother protocols such as Lon, Modbus and EnOcean.
About Thermokon Sensortechnik GmbH
Thermokon has specialized in the production of sensors for the HVAC- andbuilding control technology. Thermokon ensures an ideal exhaustion of saving
potentials, e.g. by offering individually matching solutions. The receiver SRCBACnet enables the connection of EnOcean sensors and wireless switches to
BACnet.

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About the EnOcean Alliance
Leading companies worldwide from the building sector collected to form the
EnOcean Alliance and establish innovative automation solutions forsustainable building projects – and so to make buildings more energyefficient, more flexible and lower in cost. The core technology of the Allianceis self-powered wireless technology from EnOcean for flexibly positioned andservice-free sensor solutions. The EnOcean Alliance aims to standardise andinternationalise EnOcean wireless technology, and is dedicated to creatinginteroperability between the products of OEM partners. More than 120
companies currently belong to the EnOcean Alliance. The headquarters of the
non-profit organisation is located in San Ramon, California.
EnOcean®, alliance logo, alliance member logo and ingredient logo are
registered trademarks of EnOcean GmbH and EnOcean Alliance Inc.

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