A new type of floor duct integrates an easily variable,
under floor air-conditioning system with the finished
floor layer.
What would you say if I told you that the type of floor
you specify could qualify as tax-deductible expenditure?
Not just the materials or the services underneath it
but the substrate, the support layers and even, possibly,
the floor finish. What’s more, all of this could be
depreciated and set off against general income at the
year end, all legal and above board in accordance with
Capital Allowances rules and regulations. Imagine mentioning
it in an early design meeting with the quantity surveyor,
and picture how the client would sit up and listen.
Well, have I got your attention?
The new floor system manufactured by Stockholm-based
company, Protek, and marketed in this country through
its London offices offers such a benefit. The system
comprises a raised floor deck supported off the structural
floor slab by a variable-height steel substructure.
Effectively, it is a similar system to most service
duct floors, raising the floor to provide a serviceable
space below in which to locate services.
The floor decking layer comprises square panels of
high-density chipboard or fibre-reinforced calcium silicate
board, faced with a wide choice of finishes—from marble
and oak laminate to slate. These panels are set on
top of the support grid rather than inset into a channel,
meaning there is scope for the flooring to be laid with
no gaps. The support steel grid provides an edge bearing
for the decking of about 20-30mm (depending on the loading
requirements) and a rubberised cover strip over the
top of the support framework ensures a tight seal and
impact sound deadening. The seal with the steel supports
and the fine tolerances between each floor square are
important in preventing air leakage draughts from the
void below into the habitable spaces above.
Raised service floors are the reflected plan of suspended
ceilings, performing many of the functions that the
traditional ceiling void enables. By locating the service
void at floor level, however, access is more manageable;
electricity feeds can rise conveniently to floor terminals
rather than in drops; pipework risers to radiators are
easily accommodated and, if the soffit is suitable finished,
the suspended ceiling can be eliminated. At a show
office in Clerkenwell, London, the oak veneer flooring
and matt white walls were illuminated by beautifully
designed floor-mounted uplighters and task lighting
only, eliminating the need for soffit cabling and ceiling-mounted
fluorescents.
As an aside, when I first visited Tate Modern before
it opened, one of the many unattractive finishing treatments
– apart from the architraves, the inappropriate door
ironmongery, the non-flushness of wall surfaces and
the Heath Robinson light boxes – was the allegedly minimalist
shadow gap between floor and walls, which proved elusively
difficult for ham-fisted workmen to achieve with panache.
With the best will in the world, any movement in the
floor level was bound to show up as discrepancies in
this tolerance gap. With a raised floor, plaster finishes
can be taken down to floor level (beyond the line of
the floor finish) without the need for skirtings, making
a very neat line with the floor finish.
Carpet Tax
The key aspect of Protek’s flooring is that it is classified
not as a floor but as a ventilation system, whereby
its under floor void acts as the air-conditioning duct
space. Instead of air being brought into the room by
purpose-made ducts, the floor is the ‘ductwork’
– the depth between the structural floor and the underside
of the flooring (usually 280 mm) over the full surface
area of the open floor plan. Therefore, the floor void
is used entirely for the distribution of clean, conditioned
air, which has been recirculated by decentralised zone
units.
The fact that the system can honestly be described
as an air-conditioning plenum qualifies it as tax-deductible
PMFF (plant, machinery, fixture and fittings). Depending
on the surface veneer adding weight for acoustic deadening,
even the finish could be classified as an essential
element in the service provision requirements.
Outside air is drawn in and mixed with return air from
the room, which is then filtered, cooled (or heated)
and introduced into the raised plenum floor. As the
air circulates under the floor, it is drawn up through
fan-based units which, at different controllable speeds,
push the conditioned air into the room through floor-mounted
grilles. These units have up to five speeds but are
fitted with low-noise fan assemblies. The high density
of the calcium sulphate flooring squares (1.45 kg/m3
– so that the 600mm x 600mm x 36mm panels weight about
53 kg/m3) ensures that the floor makes a
satisfactory bond with the support framework and deadens
the faint noise of the fans (about 46 dBA with loose
laid tiles).
Comfort Zones
Dedicated space must be provided for the zone handling
air conditioning unit, which controls the filtration
of air, ventilation, cooling and heating needs and distributes
conditioned air under the floor. The air is chilled
or heated, as determined by the BMS, by water-serviced
cooling.
Heating coils in the service core and the zoned air
con unit (ZA) continuously monitor and control the air
temperature in the floor plenum and in the room for
each assigned zone. To maintain a particular controlled
zone, internal partitions should either not be taken
down to the structural slab beneath the floor or, if
this is unavoidable, fitted with ventilation grilles
to allow the free passage of air through the partition.
Care should be taken to ensure that fire barriers are
not breached, although intumescent grilles are available.
One feature of the access floor is the under floor
baffle, which creates and separates the under floor
areas, as required, into paths for supply and return
air. The baffle can be repositioned to suit user needs
for different airflow patterns and directions. Supply
and return flows are integrated into one RAG unit (a
Swedish abbreviation that apparently translates as Intelligent
Underfloor Air Terminal) at the floor grille. These
floor grilles are built into special tiles and are visible
at floor level.
The RAG units are controlled locally – to give a maximum
microclimate differential – by lifting the grille and
manually setting on-board temperature sensors and fan
speeds. The modular dampers then adjust automatically
during the cooling/heating or recycling mode and fresh
air is ensured throughout (even during recycling).
Mains electricity cables are laid in under floor power
tracks that can be plugged into at locations to suit
spurs-to-floor sockets or RAG units. Since the RAG
units have no pipework connections or duct fixings,
they are effectively free-standing, wired in only to
the mains below ground and easily connected. To access
the under floor area, floor tiles can be lifted with
the aid of the suction handle, gripping the tile to
be hoisted out of place. Such is the ease of manoeuvrability
of the individual components (although floor tiles are
sometimes heavy) that a grille, and hence RAGs and air
outlet points, can be relocated quickly and easily,
meaning that changes to workstation layouts need not
be a slave to the M&E layout, it being possible
for air ducts to follow the needs of the occupant.
One other interesting feature of the raised floor system
is that plant pots can be suck beneath the surface and
so appear to be growing out of the floor level, like
genuinely planted foliage. Personally, I prefer allowing
the soil / pebbles to appear flush with the surface
rather than the proprietary containers with visible
50mm steel rim kickers used to contain the soil, but
generally they provide a visually intriguing spectacle.
Step Change
While there are tremendous benefits to the Protek system,
care must be taken when installing it to weigh up the
pros and cons and the implications of raised floor heights
on the rest of the building. New build can easily accommodate
this floor build-up, but in refurbishments there will
be knock-on effects on door threshes (and hence lintol
heights); lift lobby heights (although air – con may
not be needed in lift lobbies, steps will be needed
to achieve the 300mm or so changes in height – check
DDA requirements for ramped access); and the Health
& Safety in the Workplace regulations on sill heights
(erstwhile sill heights of 1m, for example, will become
approximately 820mm after installation, requiring lower
panes to be in toughened glass).
In general, though, this floor system is a rival to
chilled beams, freeing up internal spaces and doing
away with the need for suspended ceilings and their
consequent time, effort and cost of step-ladder maintenance.
As usually, the best ideas tend to be the simplest.
