A zero net energy office building is one which consumes no net energy. Its an office that uses very little energy, then has some form of renewable energy to generate all the power it requires.

With current off the shelf solar technology, presuming little or no shading, its possible to get around 100 kWh  of energy per year per square meter of solar panels at latitudes of around 40 degrees, more in sunny locations at lesser lattitude. For a single storey building, with a roof covered with solar panels, and little shading, keeping office energy consumption to 100 kWh/m2 is easy, and in fact I’ve audited quite a few small offices that are nothing special but only use in the order of 100 to 120 kWh/m2. But a grid connect solar system nowdays costs in the vicinity of  $700 to $1,000 per square meter, which is pretty  expensive, so there are very few zero net energy offices in existence.

Aggressive energy conservation and use of off the shelf technology (like skylights) can mean that office energy consumption is kept down to somewhere between 30 to 50 kWh/m2, meaning only half the roof needs to covered with solar panels, or allowing for some shading. For example our office uses only 30 kWh/m2/year, but is shaded in winter, we could make it energy neutral now just by covering around 2/3rds of the roof in solar panels.

So it is possible now, in 2009, to have a zero net energy office, but its not easily affordable, yet. And if your office is 3 storeys or higher, its becomes very hard to achieve no matter what your budget.

Technological advances however, are happening rapidly and I believe that by 2020 a zero net energy low-rise office may be affordable. And importantly this should be achievable by retrofitting an existing office building, with no need to especially construct a new building. Some of these technological changes are:

• The emergence of LED lighting. Assuming by 2020 we have LED lighting of around 200 lumens per watt. Allowing for some daylighting, and good use of task lighting, it may be possible to have annual lighting use less than 8 kWh/m2/year.
• Computer efficiency improvements. Assuming that with thin client architecture and high efficiency monitors by 2020 an office PC uses 15 watts, and that a 200 watt server can then serve 30 clients, computer energy use would be around 3 to 4 kWh/m2/year.
• There are many likely pathways for HVAC, which will depend on climate. A likely pathway for temperate climates is 100% fresh air HVAC systems, with air to air heat exchangers, but also using legacy internal ducting to allow high flow full economy cycles. Fans will be highly efficient, and heat pumps will have high efficiencies at a range of loading conditions, with the conditioning of air separated from ventilation to lower fan energy use. Couple this with light weight retrofit phase change materials (PCM) to provide thermal mass (eg plasterboard with encapsulated PCM), white roofs (where there are no solar panels), glazing treatments and new insulating membrane technologies to improve the thermal performance of the building. Seal the building well, and combine with good use of sensors and intelligent control all of which limits HVAC energy use to say 15 kWh/m2/year.
• Miscellaneous loads: high efficiency fridge at say 150 kWh/year; near zero standby loss hot water system; high efficiency multi function devices, totalling say 4 kWh/m2/year.

This will result in total office energy use of around 30 kWh/m2/year.

With aggressive energy conservation occupants should be able to to get down to say 15 to 20 kWh/m2/year.

Assume solar panel efficiency is more than double current efficiency and the installed price per watt of a grid connect system is one third of the current cost. This will provide 260 kWh/m2/year at a cost of say $500 per square meter.

A single story unshaded office where aggressive energy conservation is practiced will then need only 8% of its roof covered with solar panels, at a cost per square meter of building area of only $40.

A three storey half shaded office building would need most of its roof covered.

It should be possible to have a 7 storey building energy neutral if unshaded and the roof is covered with solar panels. Of course if additional solar panels can be added to walls it should be possible to get even taller energy neutral buildings.

By 2020 the net zero energy low-rise office building should be easily affordable, and in fact it may well be standard good financial practice to convert existing office buildings to energy neutral ones. So even building owners with no interest in acting to slow climate change will have energy neutral buildings. And most low rise office buildings then - whether they are 100, 50, or 1 year old -  could be energy neutral.

I say “should” and “may” because I still have some doubt as to whether a couple of the technologies that modify the thermal performance of a building –  particularly PCMs, and retrofit membrane’s that improve its insulation properties – will be affordable. But then again with focus a lot can change in 11 years, and as more of us demand better energy performance from our buildings I believe that this will spark the innovation needed to make zero net energy office buildings common place.

You can help make this a reality by acting now to make your building more efficient. Do what is affordable now. Then repeat regularly - technology is now advancing quickly. You’ll create the demand that will drive the innovation that will create the technology that will make energy neutral buildings common place.

Building Automation Systems (BAS), otherwise known as Building Management Systems (BMS) or Direct Digital Control (DDC) systems don’t save energy. But their operators can.

A BAS system will often cost the equivalent of around one year’s worth of energy bills. But unless its well operated it may never pay itself off.

BAS systems are complicated. In this respect they are similar to a jet airplane. But unlike airline pilots, in far too many cases the operators of the BAS systems have little or no experience, minimal training, and often very little time to operate it.

You wouldn’t buy a jet airplane without having appropriately trained and experienced pilots to fly it. But far too often organisations buy BAS systems without making the necessary investment in the people who operate it.

Unlike airplane pilots, where serious mistakes can be fatal, if the BAS operator makes a mistake the chances are very few people, if any, will know about it. Your building won’t crash and burn if the operator manually over-rides a time schedule and leaves a large fan running all the time. (I haven’t seen a BAS system yet where fans that should be on a time schedule have had their schedule bypassed.)

In many organisations, with energy costs 1% of less of total operational expenditure, the chances are that the accountant won’t be watching to ensure that any savings put forward in the business case for installing the BAS are actually achieved. Usually the only thing that everyone will know about, and have an opinion on, is the temperature inside the building. In response to this many BAS operators do everything possible to keep the building at a temperature that generates the least amount of complaints, no matter what. In some cases the energy implication of this are like a pilot flying from Melbourne to Brisbane via Alice Springs to avoid a bit of turbulence, rather than making intelligent small deviations to the direct Melbourne – Brisbane route to minimise discomfort to passengers.

And if you’ve outsourced the management of your BAS, are you auditing the performance of your contractor? How do you know your BAS contractor is operating your building for high energy efficiency? The contractor doesn’t pay your energy bills – and again may end up with the sole focus of keeping the building at a temperature that minimises complaints, without necessarily considering the increased energy consumption that this may cause. One of our customers has us auditing their controls on a regular basis, and we rarely fail to identify valuable energy savings because of wastage caused by shortcuts taken by their contractors.

Also unlike in an aircraft, when an alarm is raised by the system, the chances are that it will be ignored. Particularly if there are dozens or even hundreds of alarms going off every day, which is the norm rather than the exception in larger BAS systems.

And unlike a new jet, the chances are that your brand new BAS system may not have been correctly commissioned. For example one or more sensors could be in the wrong position and thus giving erroneous readings. An example is a recent customer’s building where the building manager couldn’t figure out why the system was running on 100% outside air most the time. After a great deal of investigation it turned out that the CO2 sensor (air quality sensor) was positioned in a copier room which had no mechanical ventilation (another mistake), and was thus reading too high, with the result that the system was running on 100% fresh air - at huge energy cost - to try and reduce CO2 levels.

To get the most from you BAS system invest in the person who runs it. Make sure they know the principles of energy efficient HVAC and building operation. Make sure they are well trained in operating your system. Set energy performance targets, and monitor them. Make sure they have enough time to actively operate the system, and aren’t just spending all their time dealing with alarms. Bring in experts to help configure the system and review it on a regular basis if necessary. Or else outsource management, but with clear performance targets and regular audits if necessary. And then the investment in your BAS will result in energy savings.