Danfoss Planning Underfloor Heat Compendium
MAKING MODERN LIVING POSSIBLE
Planning Underfloor Heat
DANFOSS HEATING SOLUTIONS Handbook
Handbook Planning Underfloor Heat
Planning criteria
Standards for
underfloor heating
Essential requirements for all calculations:
• Detailed plan of building, construction of outer
walls, and size and type of windows.
These data are essential for calculation of the
heating load in accordance with EN 12831.
• Information on the type of ooring and its
thermal resistance R
dependent on the oor construction, particularly
, since the heat output is
λ,B
that over screed (in accordance with EN 1264 a
thermal resistance of R
living rooms is specied, in bathrooms R
m2 K/W. Other values up to a maximum of 0.15
m2 K/W are to be separately agreed.) R
m2 K/W.
= 0.1 m2 K/W R
λ,B
λ,B
for
λ,B
= 0.0
λ,B
= 0.0
• Building plans, building drawings and all room
data have to be shown. After the calculations,
the pipe layout and data are included in the
building plan.
• Danfoss forms for calculations.
The following standards have to be observed when
planning and installing oor heating:
EN 1991 Action on structures
EN 1264 Underoor Heating, Systems and
Components
Changes in building methods over the last few
decades have brought about lower requirements
for heating homes, so that Danfoss underoor
heating can meet respective heating requirements
for even physiologically acceptable surface temperatures. In some rooms, such as bathrooms,
additional heating may be necessary, as areas
under bath and shower cannot be heated and
a higher temperature is required (24° C instead
of 20° C). In such rooms the underoor heating
maintains the temperature in the oor while other
heat comes from sources such as wall heating,
heated towel rails, etc.
EN 13813 Screed Material and Floor Screeds
Local building regulations.
Professional information on interface
co-ordination when planning heated
underoor constructions (ref: BVF).
Estimated
pre-calculations
DIN 4109 Sound Insulation in the Building
Industry
ISO EN 140-8 Measurement of sound insulation
in buildings and building elements
The output tables of Danfoss SpeedUp and Basic
heating systems show output values for various
room temperatures as well as the temperatures of
the central heating water in relation to dierent
oor nishes. These tables give calculations of the
mean central heating water temperature with
which to run the underoor heating in order to
achieve the desired output.
EN 1264 is crucial for the construction of underoor heating. With the inclusion of EN 13813
‘Screed Material and Floor Screeds’ three Basic
Danfoss constructions are possible.
The required excess heat source temperature
determines the supply temperature which is
described in more detail in the chapter ‘Calculating
the supply Temperature’. The heat ow densities
are distributed evenly over the edge and comfort
zones. The main central heating water temperature is determined by the type of installation (see
output tables).
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VGCTC202 © Danfoss 06/2009
max 29°C
W
Handbook Planning Underfloor Heat
Standard heating load of
an underfloor heated
room
Thermal insulation to
avoid downward heat
loss
When making calculations for Danfoss underoor
heating the standard heat load Q
essential. For underoor heating in multi-storey
of the room is
N,f
buildings the heat gain of the shared oor can be
included into the calculations if there are no
restrictions on the work.
The heat output QH is generally calculated from
the standard heat load of an underoor heated
room Q
accordance with EN 4701 Part 3.
plus an extra calculation allowance in
H,f
QH = (1 + x)* Q
N,f
It is important to consider the thermal resistance
of the insulation below the underoor heating so
that the heat of the underoor heating radiates
mainly upwards.
In accordance with EN 1264, Part 4 there are three
dierent kinds of oor/storey constructions and
various minimum heat resistances.
Thermal Insulation R
A above rooms with similar use 0.75 m2 K / W
B above rooms with dierent
use*, unheated rooms (e.g.
cellar) and on ground oor
C above external air (-15°C) (e.g.
garages, passage ways)
* e.g. rooms above commercially used premises
1.25 m
2.00 m
Ins, min
2
2
K / W
K / W
Q
: Standard heating load of an underoor
N,f
heated room [W]
QH: Heat output calculation
If the heating system, such as an underoor
system, can raise the heat output by raising the
heat source temperature the extra allowance is is
zero. Thus the calculated temperature output
equals the standard heat load of an underoor
heated room.
The heat resistance R
layer is calculated as follows:
R
with a single insulation
λ.ins
S
=
λ,ins
λ
ins
ins
with:
S
: eective insulation thickness [m]
ins
λ
: thermal conductivity [W/m K]
ins
Maximum surface
temperature Θ
Fmax
Fluctuation in
temperature (W)
In accordance with EN 1264 maximum surface
temperatures for phsysiological reasons are set
as follows:
Comfort zone: 29° C
Edge zone: 35° C
Bathrooms: ti + 9° C = 33° C
Standard room temperatures of 20 or 24° C
in bathrooms result in a dierence in surface
The position of the heating pipe can further
inuence the output. Depending on the position,
varying surface temperatures can occur. Output
is higher above the pipes than in between. The
dierence between the maximum and minimum
surface temperatures is called uctuation (W).
W = θ
F max
- θ
F min
Larger distances between pipes cause larger
uctuation. Lower lying pipes slow down the heating
sy stem but the ‘ long w ay’ to the sur fac e dis tribu tes
the temperature evenly, the uctuation remains
small. Since the maximum oor temperature must
not be exceeded, larger uctuation causes greater
loss in output than a smaller uctuation. In the rst
temperature and room temperature of 9K (in
comfort zones and bathrooms) or 15K (in edge
zones). Limiting the surface temperature has
the eect of limiting the heat output of the
underoor heating. It is an important factor when
deciding whether to choose additional heating.
However, with modern insulation the heat output
in underoor heating is sucient in 99 of 100
cases.
case, average oor temperature is signicantly lower
than the maximum permitted temperature.
VGCTC202 © Danfoss 06/2009
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