Rehau STAR 20 Installation Manuallines page 18

Insulation
A layer of insulation should be laid immediately below the heating
pipes to prevent downward heat losses. For screeded fl oors, REHAU
normally supplies a plastic Clip Rail for fi xing the pipework. Clip Rail
is laid onto the insulation to which the pipes are attached. This means
that the client can use the insulation material of his choice to lay
underneath the fi xing system.
Minimum insulation thickness and type should be specifi ed by
the architect and/or builder to comply with the current Building
Regulations.
Thermal Response Time
The better the U-value of the building and the higher the degree
of insulation, the faster the response time of the system.
In wooden suspended or fl oating fl oors, system response time is
comparable to a radiator system. However, there is no thermal lag with
these types of fl oor construction and good levels of insulation
are required under these systems. Where it is necessary to allow a
small gap between the insulation and the UFH system, there must be
no air movement in this air gap.
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Where the UFH system is to be installed in wooden suspended ground
fl oors with an open void below, all air movement must be prevented
between the insulation and the UFH system to ensure maximum
effi ciency from the heating system.
For systems installed in screed operating on a daily basis, the
response time is fast. This is because the temperature drop during
"off" periods of up to 8 hours is of the order of only 3°C due to the
thermal lag in the fl oor created by the energy stored in the screed.
By carefully setting the system time clock, comfort can be maximised
whilst minimising the system "on" time.
Sound Insulation
Depending on the type of insulation installed, the insulation will
provide a degree of sound insulation. If a specifi c level of sound
insulation is specifi ed, details must be advised to the design team
before the design process begins.