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H VA C
Going underground
Consultant, Andrew Wilkes, looks at one of the flipsides of the recession – how it is actually helping
revitalise the nation’s commercial building stock and steering designers and investors towards
efficient, flexible and energy saving thermal comfort solutions.
L
ooking at the significant option. Not simply in – minimising vacancy periods.
number of mixed use environmental terms but in the Previously, when planning
and commercial basic economics of investment guidelines were less stringent
buildings planned for value. Although cynics among and the banks were more ready
London that have us would point to the fact that it to make enormous advances to
succumbed to the deepening could be simply financial speculative developers, there
recession, it would be constraints and the collapse of was less incentive to recycle
reasonable to conclude that the construction side of things commercial buildings.
commercial developers would that has shifted focus, Additionally, retrofitting building
be in the depths of despair. efficiency, in every sense of the services with traditional
Indeed, some are. However, word, is now vital. solutions is difficult both
many projects are still being What this means for building practically and financially. Many
designed in the capital and services engineers is that existing buildings do not have
there’s a definite air of optimism projects are under way but only high enough ceilings to easily
amongst some of the more where innovative and added- retrofit traditional VAV or fan
lateral-thinking developers. value solutions are integrated. coil air conditioning – ceiling
This may come as a surprise, Building owners are facing a voids of 600mm often being
at first glance – how could there hugely competitive market with necessary – resulting in either
be talk of investors and building a tenant base that’s not willing major structural changes or
owners making any sort of to sign up to a long term lease consignment to a second class
money with the City seemingly and is able to select from a existence and investment value.
crumbling around us? After all, growing number of vacant However, an environmentally
a number of these development premises. Much of the available responsible solution
teams had been behind the now stock is high in energy use and acknowledged by architects and
extinct projects that would have totally reliant upon electro- consultants as being ideal for
become key landmarks on the mechanical cooling. The smart refurbishment projects is
London skyline. investors have realised that underfloor air delivery. system. Depending on the system with fan-assisted floor Overcoming the problem of
Nevertheless, it is no surprise flexible and effective building Underfloor systems offer nature of the installation, AET tiles, a shallow depth floor void discomfort traditionally
to me that there remains an services are the primary means energy efficiency for the tenant are in a position to offer a allowed the floorplates to be associated with VAV solutions,
amount of buoyancy, as those of ensuring that one property wishing to keep costs capped combination of air conditioning brought up to modern day PleinAir incorporates a unique
with office portfolios are simply stands out above another. and flexibility for the investor systems to suit. standards creating low energy, AirSwitch damper using time
redirecting their attention. This is particularly the case that needs to be adaptable to a With underfloor air, the floor flexible and comfortable modulation control – a new
Shelving (or being forced to with thermal comfort solutions. changing tenant base, switching void can easily be used as a workplaces that have received control technique for managing
shelve) new construction Yes, we want to ensure that floorplans to meet demand and plenum to distribute plaudits from tenants and the the way conditioned air is
projects in favour of addressing we’re specifying the most maximise the longevity of a conditioned air to office space landlord alike. introduced into a space and an
the performance of existing energy efficient building property investment. instead of installing a mass of additional feature that stands
stock, renovating and bringing services but air conditioning Additionally, increased office ductwork and equipment in the Low carbon package PleinAir above previous
building services up to date can never be considered productivity and thermal ceilings. Using a raised access AET’s new VAV underfloor underfloor VAV systems. This
seems to some a less attractive entirely green. However, for comfort satisfaction are floor instead of deep false system, PleinAir is a low carbon new device eliminates instances
investment over a new project. office space in our urban reported in post-occupancy ceiling void brings a net height package with energy reduction of poor air distribution at part
Yet, as a means of hugely centres, temperature limits are evaluation surveys. saving per floor of and versatility its prime load conditions in fixed slot VAV
raising rentable value within a frequently a prerequisite of any approximately 450mm, since concerns. For instance, the roof- terminals and the improvement
current portfolio, it is now the tenancy agreement and there Ideal for retrofit there is a minimal space mounted all air central plant can in air distribution is immediately
way many developers are doing are proven systems that suit Where underfloor air has requirement for ceiling voids. allow free cooling via the noticeable to users as well as
business. The excesses of refurbishment projects perfectly advanced in recent years and Coupling the delivery method versatile PTUs, when the lowering energy input by
building new, it seems, fell by – both maximising energy become the ideal solution for with supply air either drawn up ambient temperature is less than effective air-mixing to occupied
the wayside at the start of this efficiency through free cooling retrofit is its adaptability – AET’s into the occupied space by fan 18˚C – which is 84% of the year zones.
new era when obvious waste is and those that are adaptable to Flexible Space Concept for assisted terminal units on the in non-coastal areas, on average. For investors, whole life costs
just not acceptable. a degree that ensures office example, a CAM and HIVAR CAM system or through central Combined with the range of and embodied energy have
churn can be swiftly undertaken based system that has now plant fed, low terminal pressure either square or round high become increasingly important
Refurbishment been expanded to include an passive tile units (PTUs) on the induction floor grilles which in construction and developers
Refurbishment has without underfloor VAV new PleinAir VAV system, provide up to 16 different air have been forced to adopt much
doubt become the allows for minimal intrusion patterns of varying intensity, the more sustainable options by
sustainable into valuable net-lettable space, Variable Air Volume and low Legislative pressures. Recycling
as well as giving the advantage terminal pressure (between 7 rather than starting from
of easy reconfiguration. and 12.5 Pascals) makes scratch is a key way to keep a
There are numerous PleinAir one of the most energy building’s carbon footprint low
examples of the effective use of efficient cooling systems – up to but, accompanied by the reality
underfloor air delivery in a 14% reduction in running costs that offices users still demand
refurbishment projects. One is compared to a conventional fan high thermal comfort
the 165,000sq ft Tricorn House coil system. Adding outdoor air conditions, these must be
building erected in the early volumes above the Building provided in both the most
1970s that was moving towards Regulations minimum can raise efficient and flexible manner.
demolition and replacement on this reduction to over 60% - Underfloor air is the natural
investment grounds. By using saving massive quantities of choice for these refurbishment
an underfloor air delivery carbon emissions. needs.
4 BUILDING SERVICES & ENVIRONMENTAL ENGINEER JUNE 2009
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