7 August 2013 – “Bank of America’s Toxic Tower New York’s ‘greenest’ skyscaper is actually its biggest energy hog” was the headline in the New Republic.
The recent revelation that the “ultra efficient” LEED platinum rated Bank of America tower is in reality the most energy intensive building in New York has generated much finger pointing.
Architects have cried greenwash while others point to too much low hanging fruit within the LEED scheme and the inherent limitation of measuring the building as a structure independent of its tenants.
To blame COOKFOX architects is a cheap shot. Architects have a finite capacity to influence the behavior of the companies that use the buildings they design for developers and to suggest a failure to ensure the tenant operates with energy efficiency front of mind translates to greenwashing is nonsensical. I have no reason to doubt that COOKFOX operated with absolute sincerity and diligence to deliver the greenest building within the scope of their commission.
To suggest that LEED is singularly at fault is also a gross over simplification, although there some important issues embedded in LEED’S dependence on ASHRAE (American Society of Heating Refrigeration and Air Conditioning Engineers) standards for its energy efficiency ratings that deserve further understanding.
As for the tenant, there is no doubt that if Bank of America is using nearly a third of the floor space for trading rooms this will place a significant burden on direct energy consumption, which is further amplified through the knock-on effects of increased airconditioning loads.
What doesn’t help our understanding is the spurious calculations of typical trader workstation consumption in the original New Republic article that have subsequently been repeated as if fact by others. This is despite obvious errors pointed out in the article’s own comments section.
The original article says:
“Assuming no one turns these computers off, in a year one of these desks uses roughly the energy it takes a 25-mile-per-gallon car engine to travel more than 4,500 miles.”
This is a long way from the reality of the modern desktop, whereby idle and standby power modes are extremely efficiently managed. Assuming a 24 hour flat profile of energy use at the desk is just not realistic anymore, regardless of whether the computers and screens are switched on.
Anyone attempting to predict a NABERs rating for a new building in Australia will understand exactly how much impact assumptions over the diversity of equipment power usage has upon the air conditioning loads.
A concerning lack of data but no shortage of opinion
What is most concerning about the recent coverage is that accusations and post mortems are being made with the scantest piece of useful data to work from.
Was the energy intensity that caused the outcry for the whole building or just the base building? Was the data collected by the City of New York for comparison done on an equal and fair basis – that is, were all buildings consistently metered and all fuel sources included?
These methodological approaches can make a difference to the published energy intensity for the building far greater than any low energy building initiative. But data collection is boring and there is no established leader in the field to pull down a few pegs.
So putting aside the lack of quality data with which to draw meaningful conclusions, there remains two elements of how we rate and benchmark buildings that are worth exploring.
Firstly, are we correct in rating a building abstracted from its tenants and users? Absolutely.
Decisions are made at many stages in the delivery of a new building, many of which are resolved long before the ultimate tenant is even known.
To ignore the auditing of these decisions against their environmental impact until the tenant and their behavior is demonstrated in operation will mean 95 per cent of opportunities to green the building will be missed.
Dismissal of design ratings versus the more “pure” performance ratings conveniently
ignores elements like sustainable materials, toxics, natural light
and other design outcomes that are not impacted in any way by who the tenant is
Moreover, the growing dismissal of design ratings versus the more “pure” performance ratings conveniently ignores elements like sustainable materials, toxics, natural light and other design outcomes that are not impacted in any way by who the tenant is.
Another important concept embedded in the approach of LEED (and Green Star) is to measure those things able to be contracted at the time of construction.
No amount of moral high grounding on the need to consider the users in situ will change the fact that they are not party to a design-and-build contract for a speculative office.
Even in the few cases where an anchor tenant is on board early enough to be party to design decisions, property investors generally demand that the base building is designed for a generic future tenant anyway to ensure the building is attractive to the widest possible market when it is inevitable re-leased.
Time for energy efficiency ratio?
One solution to factor in the uncertainty of tenants would be to change the way we think about benchmarking the energy efficiency of an office. Rather than judging the energy efficiency of an office against an absolute benchmark of kgCO2 a square metre, or kWh a sq m, which will always require a hypothetical tenant for airconditioning loads and lift energy to be predicted, perhaps now is the time to move to an efficiency ratio or coefficient of performance (COP) benchmark.
A building with an efficiency ratio or COP of 1 would require an additional 1kWh of energy to operate for every 1 kWh of energy consumed by the tenant. If the tenant runs an energy guzzling trading floor, then the building would be recognised for how well it is able to maintain its COP in the face of the increasing load.
This move would have the additional benefit of encouraging engineers to design their systems to operate efficiently for a range of tenant uses.
Until such a change in how we think about benchmarking the energy efficiency of buildings is introduced we will always be judging a building by what its current occupants have done, which is also problematic when the benchmark is used for point of sale or lease disclosure.
A prospective tenant might have a materially different business and hence impact on the buildings energy consumption that the previous one.
So I have no problem with LEEDs approach to rating the building as a discrete entity.
LEED uses energy cost
The second question arising from the Bank of America tower story is whether some of high operational energy might be due to LEED’s reliance on ASHRAE’s energy cost budget method for determining energy efficiency.
In Australia, we owe a debt to the Sustainable Energy Development Authority of NSW (SEDA) who, in 1999, set the standard for benchmarking Greenhouse gas emissions in buildings. Greenhouse gas, measured in kg of CO2 equivalent makes an excellent measure and it makes good some inherent distortions when reporting simply energy.
For instance, electricity and gas have very different greenhouse impacts. Knowing how many MJ of energy consumed by a building means nothing when trying to understand its environmental impacts. The greenhouse metric also incentivises fuel switching to greener sources of energy. With this knowledge it is difficult to understand how you can measure the environmental impact with any other metric.
The Energy Cost Budget Method defined by ASHRAE and adopted by LEED uses the dollar cost of purchased energy as its ultimate measure. This incentivises the use of cheaper fuel sources, which we know clearly has no correlation to reduced environmental impact. It also encourages systems that load shift to off-peak supply tariffs.
The ice storage question
This “cost basis” way of assessing energy efficiency likely led the designers of the Bank of America tower to adopt 5MW of ice storage systems for the airconditioning plant. This is seriously large system and upon first hearing of the proposal I raised concerns with one of the large ice storage manufacturers.
We had scrutinised such systems in the past and while they can save money by leveraging cheap overnight tariffs they are also likely to cost significantly more greenhouse gas emissions due to the increased quantity of energy required to create the ice, which requires chilling fluid below zero degrees.
It was suggested to me that overnight energy in New York had little or no greenhouse emissions and therefore my concerns were not valid. My continued pushing that greenhouse gas intensities for New York are not published in a time of use tariffs made little difference to the marketing pitch.
A 2010 report by the Pew Centre on Global Climate Change suggested that the effect of shifting consumption from peak periods to off-peak periods could actually result in increased emissions (a typical baseload coal plant may emit 60 per cent more CO2 per kWh than a natural gas peaking unit), which would further compound the inappropriateness of ice storage as a greenhouse gas abatement initiative.
It appears that energy benchmarking for buildings in the City of New York uses the US EPA’s Energy Star’s Energy Use Indicator, or EUI, meaning it is likely that the ice storage system would be correctly accounted for.
Unlike the ASHRAE standard, it does not introduce any energy purchase cost component so would not effectively discount the value of energy consumed in off peak. This difference in energy accounting methodologies would in itself explain some of the differences between assessed and actual energy consumption.
The Energy Cost Basis Method for assessing energy efficiency within LEED appears at best outmoded and at worst capable of producing outcomes that are worse for the environment. The fix seems simple – LEED could mandate the replacement ASHRAE’s purchased energy rates for each fuel source with a greenhouse gas intensity.
I hope that the attention given to this building and its “toxic” performance creates some constructive dialogue. Until then, it’s premature to judge the building designers or cry foul generally about LEED.
What is clear is that spurious and/or context-less performance data is perhaps worse than no data at all, particularly in an environment of politically toxicity around climate change. It is also clear that Australia acceptance of carbon intensity as a meaningful indicator has served us well from a design perspective.
However, our emerging data set from the Commercial Building Disclosure Scheme could also cause some misdirected finger pointing if the reality of tenant influence and other “normilasations” are not fully understood by those looking for headlines.
Ché Wall is director of Flux Consultants and a co-founder of the Green Building Council of Australia