6
PRINCIPLES OF UNDERFLOOR HEATING/COOLING
PRINCIPLE OF UFC
Advantages of a Underfloor
Cooling System
- High level of comfort
- Draughts do not occur
- Low investment costs
- Low annual costs
- Preserves resources
- Unrestricted interior design.
Thermal comfort
The thermal comfort for one person
in a room is determined by:
- The person’s activity
- The person’s clothes
- Air temperature
- Air speed
- Air humidity
- Surface temperatures.
The heat output of the human
body occurs via main three
mechanisms:
- Radiation
- Evaporation
- Convection.
The human body experiences the
greatest level of well being if it
can regulate at least 50% of its
heat output through radiation.
With the REHAU underfloor
cooling system the energy
exchange between people and
cooling surface occurs across
large areas and predominantly
through radiation and thus
provides the optimum conditions
for a comfortable room
atmosphere.
1.0
1.2
Classic air conditioning
systems
Traditional air conditioning
systems overcome the cooling
loads that occur by changing
the air, with the following
negative effects:
- Draughts
- High room air speeds
- Cold supply air temperatures
- High sound level.
This can often result in
uncomfortable air conditions for
the user, also referred to as sick
building syndrome.
Economic disadvantages of
traditional air conditioning units:
- High investment costs
- High annual running costs.
Cooling capacity
The standard cooling capacity
of the REHAU underfloor cooling
system is 50W/m
2
in accordance
with DIN 4715-1.
The performance estimation was
carried out with:
- RAUFIX system
- Distance between pipes 10cm
- RAUTHERM S 16 x 1.5mm
- Coolant temperature 10K
- Temperature spread 2K.
Under practical conditions, with
- surface temperature of 19-20ºC
- room temperature of 26ºC
values of 35-40 W/m
2
can be
obtained.
Influencing factors on the cooling capacity
The sub-surface cooling system’s maximum achievable output is
dependent upon:
- floor covering
- pipe spacing
- pipe dimensions
- floor construction
- heat gains
- system
However, each of the factors affects the cooling capacity to a
different degree.
The floor covering and pipe spacing have a substantial impact on
the output of the cooling system.
It is recommended that only stone, tile or slate type floor or
other low resistivity floor coverings are used to maximise the
cooling output
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