MAKING MODERN LIVING POSSIBLE
Introduction to Hydronic Floor Heating
DANFOSS HEATING SOLUTIONS Handbook
Handbook Introduction to Hydronic Floor Heating
Index
Page
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Why choose floor heating? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Where can floor heating be used?. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Energy consumption . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Comfort and user behaviour . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Temperatures in the room. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Optimum floor temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Temperature distribution in the room . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Heat loss . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Floor heating system dimensioning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
For all heat sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Individual room temperature regulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Floor construction and system performance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
2
VGDYA202 © Danfoss 02/2010
Handbook Introduction to Hydronic Floor Heating
Introduction
Why choose
floor heating?
In recent years, underfloor heating has become
increasingly popular. This is due to the fact that
underfloor heating provides a range of opportunities
not offered by traditional heating methods both in
residential and commercial buildings.
However, underfloor heating also offers some
challenges and in order to make the very most
of the opportunities it is important to choose the
right solutions with regard to floor construction and
regulation method.
In most countries, floor heating is the preferred
heating method in new buildings. This is particularly
the case in residential properties, but in office
No ‘”ugly’” radiators which require cleaning.
Furniture can be placed as required without having to take radiators into
consideration.
Danfoss offers a versatile range of products for
complete floor heating systems which are all based
on two main principles:
• Danfoss oor heating solutions are optimized for
easy, fast and safe, installation by the installer
• Danfoss oor heating solutions ensure that the
end-users experience optimal thermal comfort at
minimal energy consumption
buildings and other commercial properties it is
also increasingly popular. Floor heating gives the
end-user a number of benefits:
Floor heating provides comfortable heating as your feet are kept warm while your
head is kept slightly cooler. Most people find this difference in temperature between
feet and head most comfortable.
There is currently a tendency to prefer wood and tiled floors over carpeting. It is
exactly for these ‘”cold’” materials that floor heating can provide extra comfort.
As floor heating supplies heat to the entire room, the differences in temperature that
occur between a radiator and the furthest corner of the room are avoided.
Currently, people are focusing much more on their indoor climate. Increasing
numbers are plagued by asthma and allergic problems and it is therefore important
that thorough cleaning of the home is made possible. Floor heating makes cleaning
much easier. In addition – due to the large heating surface – floor heating means that
less air is mixed and thereby less dust occurs in the room.
Everyone is familiar with the problem of water on the bathroom floor. With floor
heating, water evaporates quickly and the floor quickly becomes dry and warm
again.
With floor heating the room temperature can be lowered 1-2 °C which means energy
savings of 6-12 %.
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Handbook Introduction to Hydronic Floor Heating
Where can floor heating
be used?
Energy consumption
As long as the floor heating system is properly
designed and installed with regard to floor construction, cover, materials, etc., there are practically
no limits to where it can be used.
• Floor heating can be used for all oor nishes, tiled
floors, wood (solid/parquet), linoleum and carpeting (although the output temperature must be
calculated accordingly)
• Floor heating can be used in all new buildings
• For renovation of existing buildings the installation
height may be a limiting factor, but for this type
of application products like the Danfoss SpeedUp™
and SpeedUp Eco™ systems offering very low builtin height are available
The heat consumption of floor heating has been a
much-discussed issue for many years. There have
been many claims about rising heating bills for floor
heating instead of more traditional radiator systems.
When floor heating was originally introduced, house
constructions were not changed and floor heating
was simply installed by running floor heating pipes
in floors, which otherwise were constructed as
usual.
As the floor heating pipes are embedded in the floor,
automatically, there is a greater heat loss downwards
and thereby a negative effect on the heating bill.
• For renovation of single rooms, oor heating connected to the existing heating system and
equipped with a self-acting regulating valve, can
be a good and an economical solution
• For installation of oor heating in the entire property, wireless controls like Danfoss CF2 control system is a great advantage, because no electrical
cables need to be wired
• Floor heating can be used with all heating supply
systems. However, the output temperature must
be adjusted so that the floor surface temperature
never exceeds the recommended value (e.g. recommended by the wooden floor supplier).
Today, things have changed – the floor construction
is insulated far better than before and now special
requirements are in place for the installation of floor
heating.
This means heat loss from the building is now typically equally good for houses heated with floor
heating systems as for houses heated with more
traditional heating systems.
But other factors affect energy consumption when
comparing floor heating to other heating options
namely user behaviour and personal comfort. Most
people find it most comfortable to keep their head
a couple of degrees cooler than their feet and the
room temperature when using floor heating can
therefore advantageously be reduced by 1-2 °C in
comparison to traditional radiators, which means
energy savings of 6-12 %.
Comfort and
user behaviour
4
In contrast, most people feel comfortable with warm
fe et – an d the floo r tem per ature can t hen be so h igh
th at t he roo m te mp er atu re b ec ome s u nco mfo rt ab le,
e.g. in bathrooms with tiled floors.
The above examples of user behaviour pull in
different directions when it comes to energy
consumption and show that it can be difficult to
provide an unambiguous answer to what floor
heating means for energy consumption as this will
depend very much on the individual consumer.
However, it can be concluded that compared
to other heating systems floor heating - if used
correctly - will save energy and at the same time
provide better comfort for the end-user.
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Handbook Introduction to Hydronic Floor Heating
23 ˚C
21 ˚C
19 ˚C
19 ˚C
21 ˚C
23 ˚C
0
5 10 15 20 25 27,5 30 35 40 45 °C22,5
20
40
60
80
%
Dissatisfied %
Floor Temperature
Temperatures
in the room
The temperature experienced in a room is the result
of two different factors, air temperature and ambient
radiation, i.e. from the heated elements in the room.
It can be an advantage in many ways that heat
radiation constitutes a relatively high part of the
”overall” temperature or the operative temperature
as it is also called. If a large part of the operative
temperature is made up of the air temperature, it
means that there will be a high convection or mixing
of air in the room.
If there is high mixing, air is whirled around which
can be bothersome as well as mean a higher dust
content in the air and thereby a poorer air quality.
The way convection/ radiation occurs with radiators
and floor heating respectively can be seen below.
As can be seen, with radiator systems the air
temperature or convection makes up approx. 70 % of
the operative temperature. This is also logical if you
think about how a radiator has quite a small surface
from which to transfer heat to the whole room.
Conversely, floor heating supplies heat through a
very large surface evenly distributed in the room
which means that the ratio is just the reverse with
70 % of the operative temperature being added
by radiation.
C
R
R
C
Radiators: 70 % convection/30 % radiation
R
R
R
Floor heating: 30 % convection/70 % radiation
Optimum floor
temperature
People differ in their perception of what a
comfortable temperature is. It is therefore not
possible to define an optimum floor temperature
to suit everyone. Recommendations for floor surface
temp era ture s can o nly be prov ide d to e nsure that a
minimum number of people are ‘dissatisfied’.
The figure illustrates that at any given temperature
there will always be approx. 10% who will not think
that the temperature is comfortable.
Typically, it is recommended that floor heating
temperatures should fall within the following ranges:
living areas 19-24 °C and bathrooms 24-29 °C.
A minimum number of dissatisfied people will be
found in these ranges.
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Handbook Introduction to Hydronic Floor Heating
18 19 20 21 22
1.8 m
0.1 m
2.7 m
18 19 20 21 22 18 19 20 21 22 18 19 20 21 22
Ideal heating Floor heating Ceiling heating Radiators
0
21 3 4 5 7 8 9 10 116
20
10
30
50
70
40
60
80
Dissatisfied %
Vertical temperature differens
Temperature
distribution
in the room
In practice, it is not possible to maintain the same
temperature everywhere in a room. As warm air
rises, there will always be a flow of warm air from
the heat source towards the ceiling.
This temperature difference should not be too
large. For vertical temperature differences, it is
recommended that a difference of approx. 2 °C
between floor and head height should be maintained.
This is because most people want to have warm feet
while keeping ‘a cool head’.
But the difference in temperature should not exceed
approx. 3 °C as the body will become ‘confused’ and
comfort is reduced.
The diagram below illustrates how the temperature
is distributed vertically with different types of
heating. As can be seen, the vertical temperature
distribution for floor heating is almost identical to
the ideal distribution.
This means that the average temperature for floor
heating can often be reduced without compromising
on comfort and this means that energy consumption
falls.
Heat loss
Sudden heat loss may occur - especially in older
buildings or in commercial buildings with large/
high windows.
Heat losses occur when insulation in part of a
building - e.g. a window - is not efficient and a large
difference in temperature arises between the areas
near the ceiling of the room and the floor surface.
This temperature difference means that the air is
cooled significantly near the building’s ceiling and as cold air is heavier than warm air - the air ‘falls’ down
towards the floor at a relatively high speed.
This can be a nuisance and create draught problems.
To counteract this problem, the heat source is
typically placed in the location where heat loss is
expected so that an opposite, upward air flow is
created to offset it.
With floor heating this option is not possible as the
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heat output covers the whole floor. However, several
options exist to alleviate any such problems:
• Low energy windows with more ecient insulation
can be used.
• The oor heating pipes can be laid at smaller
intervals to increase the effect where required
(please note that any stipulated max. surface
temperature must still not be exceeded).
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• It can be ensured that the oor heating supply pipe
is placed in the problem area.
• Window constructions can be optimised - e.g. a
projection to break the cold air flow.
• Supplementary heating can be installed in the
form of convectors.
Handbook Introduction to Hydronic Floor Heating
Floor heating system
dimensioning
Floor heating is a low-temperature heating
system and there will usually be a need to mix
the temperature from the primary heat source to
typically 30-40 °C via a mixing circuit like Danfoss
Compact Mixing Shunt.
For a full dimensioning of a floor heating system, a
calculation programme will be required as e.g. the
calculation of supply temperature is complex and
requires detailed knowledge of heat transmission
in the floor’s different materials, etc.
In order to help the installer dimension, install and
commission the floor heating system correctly
Danfoss can - based on relevant input from the
customer - provide a number of services for the
complete floor heating system:
The main products for controlling a floor heating
system on the secondary side (low temperature
side) will typically be as illustrated below.
Master regulator
Room thermostats
Supply manifold
Return manifold
Circulation pump
Bypass valve
Supply temperature regulator
• Drawings and pipe lay out
• Product training
• Dimensioning and parts list
• Ekstensive technical documentation
• Technical and after-sales support
• Direct on-site support
Danfoss - behind you all the way
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Handbook Introduction to Hydronic Floor Heating
3 6 9 12 15 18 21 24
20
23
17
˚C
For all heat sources
Individual room
temperature regulation
The floor heating system is a low temperature system
with a typical supply temperature of 30-40 °C. This
means floor heating systems can be supplied from
alternative heat sources such as solar heat and heat
pumps. The efficiency of a heat pump varies very
much depending on what supply temperature is
required. If the water temperature supplied by the
heat pump can be reduced the efficiency of the heat
pump increases significantly, as per table.
As an example if a floor heating system is designed
for a supply temperature of 35 °C and a traditional
heating system requires e.g. 55 °C. Then the
coefficient of performance (COP) for the heat pump
will - in accordance with the table - be respectively
5.0 and 3.2. Or in other words the efficiency of the
heat pump will be 56 % better when used together
The temperatures in the rooms in which we live and
work play an important role in our wellbeing. It should
not be too hot or too cold, and the temperature must
be adjusted in relation to what we are wearing and
what we are doing at the time.
For example, office workers typically wear lighter
clothes and have a lower body temperature than
personnel packing products in the warehouse. The
room temperature should therefore be higher in the
areas where office workers carry out their tasks.
Typical room temperatures in a residential building:
23 °C
17 °C
17 °C
20 °C
20 °C
Activities and clothing vary from room to room,
which is why the temperature should be adjusted
accordingly.
with a floor heating system compared to use with a
traditional heating system.
Therefore, the Danfoss floor heating systems
combined with a Danfoss heat pump will make up
the optimal heating system with regard to energy
savings considering both the heat source and the
floor heating system.
Brine temperatur from the collector
°C -5 0 5
35 3.9 4.5 5.0
40 3.5 4.0 4.5
45 3.1 3.5 4.0
50 2.8 3.2 3.6
Supply temperature
to the housebuilding
55 2.5 2.8 3.2
The ultimate goal of temperature regulation is to
ensure maximum comfort combined with minimal
energy consumption.
This means that the heating system must constantly
ensure that the temperature is always suitable in
the different rooms, without
noticeable variations.
There are a range of factors that
must be taken into account, such
as the activities and clothing of the
people in the room, heat loss and
heat gain through windows, lights,
computers and other sources of
heat.
As a minimum, the temperature must be regulated
individually in the separate rooms or zones.
Independent tests and simulations have been carried
out with the purpose of establishing the importance
of regulating temperature in individual rooms for
people’s comfort and for energy consumption. The
results vary, depending on the house/apartment in
question, its construction and user patterns, as well
as on the test method used. However, the results
are all clear on one point – namely, they generally
support the importance of individual room temperature regulation for both comfort and energy
consumption.
It has been shown that energy savings of ~ 25% can
be gained without compromising comfort.
Bathroom
Living room
8
Bedroom
Hour
Temperature achieved with individual room temperature regulation
Temperature achieved without individual room temperature regulation
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Handbook Introduction to Hydronic Floor Heating
17.0
18.0
19.0
20.0
21.0
22.0
23.0
24.0
25.0
26.0
27.0
28.0
Date: 2002-02-07
0
2 4 6 8
10 12
14
16
18
20
22
24
Temp Setpoint,
Floor surface, Deg-C
Oper. temp Livi ng room[1], D eg-C
TAIRMEAN
17.0
18.0
19.0
20.0
21.0
22.0
23.0
24.0
25.0
26.0
27.0
Date: 2002-02-07
0 2 4 6 8 10 12 14 16 18 20 22 24
Temp Setpoint,
Floor surface temp., Deg-C
Oper. temp Livi ng room[1], Deg-C
TAIRMEAN
Floor construction and
system performance
In order to achieve best possible comfort for the
end-user, main purpose for the heating system is
to provide exactly the right amount of heat at the
right time and in the specific needed room. In order
to do so the floor heating controls must be able to
regulate each room individually.
However, this is not enough, the heat emitter - in this
case the floor - must also be taken into consideration.
Typically, floor heating systems have been based
on pipes embedded in concrete, thus making the
amount of energy stored in the heating system
very large.
Typical heavy floor with pipes embedded in concrete
This means when a room has reached the desired
temperature and the room thermostat shuts down,
the supply of warm water to the room, the floor will
still continue supplying heat until the floor surface
temperature reaches the room temperature.
This is a process which can take several hours
during which the room temperature will continue
to increase. In order to overcome this problem it is
necessary that the heat emitter reacts quickly to
sudden temperature changes in the room.
As opposed to traditional concrete floors which
are “heavy” in terms of reaction time “light” floors
constructed by insulation material and heat
distribution plates - as Danfoss SpeedUp™ and
SpeedUp Eco™ - are much quicker and allows for
a more precise control of the temperatures in the
room.
Light floor (Danfoss SpeedUp™)
Example
In this example a traditional “heavy” floor is compared with the “light” Danfoss SpeedUp™ floor, both
installed in a typical one-family house.
The graphs show the development in actual temperatures over a period of 24 hours including two
set-back periods where the set-point temperature is changed from 21 °C to 17 °C.
The performance of each system is illustrated by how well the actual temperature ( ) follows
the desired set-point temperature ( ). When analyzing the graphs it is evident that the light
floor is better capable of following the desired set-point temperature than the heavy floor which is
too slow for a set-back period to have any effect. Main reason for the difference is also clearly illustrated by the graph showing floor temperature ( ) which for the light floor increase and decrease
very quickly compared to the one of the heavy floor.
"Heavy" floor construction Danfoss SpeedUp™ "light" floor construction
The simulations are worked out in the simulation programme, IDA Indoor Climate and Energy 3.0.
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Handbook Introduction to Hydronic Floor Heating
Summary
The Danfoss floor heating systems ensure optimum
comfort at all times.
The precise regulation of the CF2 wireless controls
together with the rapid response of the SpeedUp
floor panels provides you with the desired temperature in minutes; not hours, thus providing you with
energy savings and reduced costs.
10
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Handbook Introduction to Hydronic Floor Heating
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Handbook Introduction to Hydronic Floor Heating
Your Key to Optimum Floor Heating
Floor heating is much more than pipes!
The optimum floor heating solution
provides accurate temperature control,
instant heat, comfort and energy efficiency.
Danfoss will provide you with optimum
floor heating solutions.
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The Danfoss solutions rank among the
best and the most advanced in the
world; combining years of experience
with development and technical
know-how. We provide floor heating
solutions which are both quickly and
easily installed for you.
VGDYA202 © Danfoss 02/2010
Our wide range of products and our
technical expertise make Danfoss your
one-stop provider, saving you both time
and worries. And the more time you save
on installation and servicing, the more
time you have to optimise your business
opportunities.
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