Archive for the ‘ASHRAE’ Category

BACnet – Introduction

Monday, June 15th, 2009

BACnet® has turned the corner. The industry is no longer playing a wait-and-see game to assess whether the Building Automation and Control networks protocol delivers as promised.

BACnet stands for Building Automation and Control Network. BACnet is the standard that was developed by ASHRAE — in conjunction with building management organizations, system users and building system manufacturers — specifically for building automation and control equipment. In 1995, after years of development and revision, the ASHRAE Board of Directors ratified and published the standard as ASHRAE 135-1995. The standard was submitted to ANSI and, in 1995, it also became an American National Standard, ANSI/ASHRAE 135-1995.

Over the next six years, the standard underwent a number revisions and upgrades. In 2001, ASHRAE released an updated standard, ASHRAE/ANSI 135-2001. In 2003, BACnet became an international standard, ISO-16484-5.

Essentially, BACnet is a set of rules governing the exchange of data over a computer network to facilitate
interoperability of various building systems. The five interoperability areas are:

  • Data sharing
  • Alarm and event management
  • Scheduling
  • Trending
  • Device and network management

As a common communication language, BACnet makes it possible for systems from different manufacturers and/or systems designed for different building automation and control functions to work together. BACnet equipment extends to controllers, gateways, routers and diagnostic tools, and provides a means to send data to a workstation.

Main Benefits for Building Owners
The benefits of interoperability within a BACnet-based facility are obvious. In theory, virtually any automated building control function can be monitored from a single operator workstation, regardless of the control system manufacturer and without the need for gateways that translate data between different systems. This simple, seamless interface levels the playing field between manufacturers and building owners, resulting in more competitive procurement of control systems.

Empowering end users through standardization was the primary motivator for ASHRAE to form a committee that led to BACnet’s creation. The standard is especially beneficial for large facilities and campus environments, where building control and automation is extensive.

BACnet devices are limited in their effectiveness unless they can carry messages over a data network. There are a number of ways that BACnet allows this: Ethernet, Arcnet,
LON,® MS/TP, and RS-232. The BACnet standard was amended in 1997 to include BACnet/IP. To date, BACnet/IP over Ethernet has been the most common choice of BACnet networking between systems from different vendors.

BACnet is a nonproprietary, open protocol communications standard. It can be applied to practically any type of system found in buildings today, including HVAC, lighting, life safety, access control, transportation and maintenance. By design, it can use a wide range of network technologies for communications. It is a written specification that includes everything from what type of cable must be used to how to initiate a particular information request or command. Its rules are specifically designed for building automation and control equipment, covering such tasks as how to request a temperature reading, send a status alarm or establish a fan schedule.

The approach that BACnet developers took when developing the standard was that for a system to be truly interoperable, there must be some standardized agreement covering two major areas: overall system operation and individual system components. They accomplished this by using an object-oriented approach in examining, controlling, modifying and interoperating with information in different devices. The BACnet object-oriented model has two major components: objects and services.

In BACnet, objects are collections of properties, each representing some bit of information. In addition to standard defined properties, objects may include vendor-defined properties as long as they function in accordance with the standard. BACnet also defines the expected behaviour from each property for that object. What makes the object-oriented approach work is that every object and every property as defined by the system is accessible in exactly the same manner.

The process of reading or writing to a property is what BACnet calls a service. Services are the methods used by any BACnet device when it communicates with another BACnet device, including retrieving information, transmitting information or communicating an action. The standard defines a wide range of services for accessing objects and their properties.

To help ensure that products developed by different manufacturers conform to the BACnet standard, a testing laboratory was established. The laboratory tests and certifies any device for conformance with the standard. The laboratory has also developed a complete set of testing procedures that are to be used by manufacturers.

BACnet is “a data communication protocol for Building Automation and Control networks.” This data communication protocol is a set of rules developed by the BACnet committee at ASHRAE governing the exchange of data over a computer network. The rules take the form of a written specification that spells out what is required to conform to the protocol.

There are 5 different options for BACnet, each of which fills a particular niche in terms of the price/performance tradeoff. The first is Ethernet, the fastest at 10 Mbps with 100 Mbps also available. (“Mbps” stands for “millions of bits per second.”) Ethernet is also likely to be the most expensive in terms of cost per device.

There are two forms of BACnet for Ethernet. One is called BACnet Ethernet for dedicated BACnet lines and the other is BACnet for TCP called BACnet/IP which can run on a non-dedicated Ethernet line. Next comes BACnet ARCNET at 2.5 Mbps. Both Ethernet and ARCNET can use a variety of physical media including coaxial cable, twisted pairs, even fibre optic cable.

For devices with lower requirements in terms of speed, BACnet defines the BACnet MS/TP (master-slave/token-passing) network designed to run at speeds of 1 Mbps or less over twisted pair wiring (RS-485). All of these networks are examples of “local area networks” or LANs. BACnet also defines a dial-up or “point-to-point” protocol called BACnet PTP for use over phone lines or hardwired RS-232 connections. A key point is that BACnet messages can, in principle, be transported by any network technology, if and when it becomes cost-effective to do so.

BACnet is Global
BACnet is not just an American phenomenon. It has steadily gained acceptance throughout the world. Recent surveys have revealed that BACnet installations are in nearly 100 countries and on every continent, including Antarctica. That’s because the inherent interoperability of BACnet and the many enhancements over the years have given end users unprecedented freedom to mix and match building control equipment from a growing array of manufacturers.

All recommended modifications to the ASHRAE standard are published openly and anyone can comment. Suggestions for improving BACnet come from professionals throughout the world. BACnet is truly living up to its original promise of making it easier to integrate building systems with diverse functions from different manufacturers. A global network of designers, manufacturers, installers, building owners and operators are more frequently turning to BACnet as a way to make all the unique systems within a building perform as a more cohesive entity. And it is rapidly becoming an international standard that is supported by technical experts from around the world. BACnet has been approved as ISO Standard 16484-5, it is a Korean national standard, and is a European pre-standard. BACnet Interest Groups have formed in Europe, the Middle East, AustralAsia and Russia to market the protocol and resolve
technical issues.

BREEAM or LEED – strengths and weaknesses of the two main environmental assessment methods

Thursday, May 21st, 2009

BREEAM has dominated environmental assessment of UK buildings for nearly 20 years, and now LEED (Leadership in Energy and Environmental Design) in the US Comparing  both schemes to find their strengths and weaknesses.Publically displaying your green credentials is becoming a must for organisations in our new sustainably-aware society. Multi-national companies are keen to show that every part of their business is green, including their buildings.

Environmental assessment of buildings is nothing new, with the first national scheme, BREEAM (the Building Research Establishment Environmental Assessment Method), appearing in 1990. BREEAM has since expanded massively, going from a 19-page BRE report with 27 credits available, to a massive 350-page technical guide (for the office version) with 105 credits.

The principles of BREEAM have also spread across the world. The US Green Building Council launched its Leadership in Energy and Environmental Design (LEED) in 1998. While similar methods have also sprung up, such as Greenstar in Australia and CASBEE in Japan, BREEAM and LEED are the main methods currently in use. And the question on everyone’s lips is: which one is best?

Spot the difference

The main difference between the two methods is the process of certification. BREEAM has trained assessors who assess the evidence against the credit criteria and report it to the BRE, who validate the assessment and issue the certificate.

While LEED does not require training, there is a credit available if an accredited professional (AP) is used. The role of the AP is to help gather the evidence and advise the client. The evidence is then submitted to the US-GBC which does the assessment and issues the certificate.

Both schemes share common components (Table 1). Early involvement of the assessor or AP at the design stage is beneficial to the project and the final rating. Both schemes drive the market to improve building design. The judging criteria also keep pace with legislative developments and current best practice.

LEED in the UK

In the UK, interest in LEED is growing. The Green Building Certification Institute’s website records 66 LEED Accredited Professionals in the UK. This is the fifth highest national total behind the US, Canada, UAE and China.

How LEED and BREEAM compare.
The US-GBC also lists ten UK buildings as being registered for one of the LEED schemes. At the time of writing, the list shows that only one UK building – the Herman Miller HQ in Cheltenham – as having gained a LEED rating. This building also had a BREEAM assessment carried out under the offices 2006 scheme, under which it was awarded an excellent rating.

Another building known to have both a BREEAM and a LEED rating is the Van de Kamp Bakery, at Los Angeles City College. The bakery gained a certified LEED rating and a Good BREEAM 2005 rating.

So it appears that BREEAM delivers a higher rating for the same building in both the US and the UK. That said, it would be more accurate to compare LEED with BREEAM 2008, as the latter now has a mandatory post-construction review, something LEED has had for a while. With previous BREEAM schemes most buildings were only assessed at a design stage.

Eszter Gulacsy, a sustainability consultant from MTT/Sustain believes LEED is simpler in its approach, while BREEAM is more academic and more rigorous. “While BREEAM is more relevant in the UK as it uses UK policies, LEED can sit alongside as part of a global corporate policy,” she says.

Gulacsy also believes that the driver for LEED in the UK is often the client’s global corporate policy or, on prestige speculative developments, the needs of global tenants. Germany-based Siemens uses it for all its new buildings worldwide, with several buildings in Europe already registered under the LEED scheme.

While some national green building councils are developing their own environmental assessment methods, some are adapting one of the existing schemes.

The BRE has not been shy about selling BREEAM across the globe. BREEAM International grew out of the BREEAM Bespoke scheme. BREEAM Europe and BREEAM Gulf are similar money-earners. But going global brings BREEAM head-to-head with its rival LEED. Ironically, BREEAM’s director, Martin Townsend, was quoted in Building Design as seeking ways of collaborative working with the US LEED system.

“If an American bank wants to build over here, it understands about LEED and wants the building built to that standard,” he said. “That’s fine, but it might not translate that well into the UK climatic environment, our building legislation or the way that building operates. Providing a client with dual certification has to be a good way of sharing that information.”

The main differences between LEED and BREEAM (courtesy Eszter Gulacsy)
Others are more cautious. “Europe thinks that LEED is an easy win, but it isn’t if the paperwork and evidence is not in place,” says Eszter Gulacsy. “There is a danger of complacency,” she warns.

The argument for two schemes

So is the dynamic tension between two competing systems desirable? Clearly, a one-size-fits-all assessment scheme would be difficult to achieve on a global basis. For example, water efficiency is a major issue in Dubai and Australia, but not in Scotland and nor in Wales. So different issues need to be ranked differently to match regional environment and regulations.

While LEED is dominated by the American ASHRAE standards, BREEAM takes it cue from European and UK legislation. The regional versions of both schemes flow from those antecedents.

BREEAM Gulf has been adapted for the local market. Gone are the Good, Very Good, and Excellent ratings, and in comes star ratings. The weightings are changed so that water is the key issue, rather than energy as in the standard UK schemes. In addition to the CIBSE guidance being the measure for certain credits, ASHRAE and other standards are also now referenced in BREEAM Gulf.

BREEAM has long been able to adapt to local contexts. With BREEAM Bespoke, for example, the assessor can work with BRE to develop assessment criteria specially tailored to a building where it doesn’t fit neatly into one of the existing schemes.

LEED, however, has not been created with this level of adaptability and it is not run that way. Instead it is fixed to the ASHRAE standards and the US way of thinking (for example, credits are awarded for having enough car parking spaces, rather than minimising them as in BREEAM).

There are also differences in the way LEED calculates credits. They are generally linked to the US Dollar (especially the energy credits), which means that if the exchange rate is unfavourable, then the building’s rating could suffer.

A key change that may make LEED more exportable is the introduction of regional bonus credits. Six regional priority credits will be available based on what the US-GBC’s regional councils and chapters deem important, environmentally, in that region.

A downside is that these credits are not available for non-US projects. However, there are national versions of LEED being developed by individual national green building councils. Canada was the first, followed by India. Countries such as Brazil and Italy are looking to have their own versions soon.

The Dutch Green Building Council has also adopted BREEAM as its favoured environmental assessment method.

There is a lot of hype about the battle between BREEAM and LEED in the UK, but this seems to be unfounded. Both seem happy to co-exist and each has their niche areas or countries. They are even borrowing each other’s ideas as they grow.

BREEAM will probably always come out on top in the UK, simply because it is imbedded in the system. Government departments require BREEAM ratings of all their buildings; most local authorities require BREEAM as part of planning approval for developments over a certain size.

Once projects are underway that aim to be zero carbon, the likes of BREEAM or LEED may have developed to become the global default methods of assessment.

Now, who’d bet against that?