24
ENVIRONMENT AND ENERGY
Underfloor hydronic
heating – a clever
solution (Part 2)
We continue our look at hydronic underfloor heating
systems, particularly considering how to choose the
right system and heat source for your application.
By Ilana Koegelenberg
CHOOSING THE RIGHT SYSTEM
Before designing an underfloor heating system, it is
important to know what you are working with. Firstly,
you need to know the heat load of the area and how
much heating is required, explains Neil Britz of Crown
Technologies.
Within any building, there would be a demand for a certain
wattage per square metre, depending on the building’s
insulation and other contributing factors such as the type
of bricks used and the resistance it offers. This helps the
team calculate the size of the system. But as it can be
tricky to get exact information from a client, they generally
work on providing 100W per square metre.
CHOOSING YOUR HEAT SOURCE
There is more to underfloor heating than just the piping,
though. How efficient and how effective your system is,
will all depend on the heat source behind it.
You also need to look at running costs — how many
hours a year the system will be required to run. This
makes a huge difference because, as mentioned before,
electrical underfloor heating costs less to install while the
running costs of hydronic is lower. Crown Technologies prefers heat pumps as a heat
source as opposed to solar, specifically where you would
need a large footprint. Not only that: with solar, it is hard
to design for both summer and winter conditions without
wasting any heat. That is why they often suggest hybrid
systems, combining solar and heat pumps. By means
of diversion of heat generated by solar collectors, it is
possible to warm Jacuzzis or swimming pools, using the
heat pumps as backup for periods of overcast weather.
It is important to determine how many loops and pipes
would be required for the system. According to Britz, the
ideal pipe run is around 100m — 120m at a push. Anything “Heat pumps are still the most efficient heat source; you
get the best coefficient of performance (COP) for the type
of installations we do,” explains Britz.
Pipes for the heated liquid
to move through being laid
on the work site.
bigger and you risk heat losses and pressure drops, making
the system inefficient. Also, the more loops you have, the
bigger the manifold has to be and the more actuators and
hardware you need. For bigger areas, they would rather
install multiple zones to get the most efficient solution.
February 2019 Volume 24 I Number 12
Pioneer also prefers using heat pumps as a heat source.
“It offers the best capital layout versus running cost,”
says Albie Schröder of Pioneer Floor Heating. He recently
did a running cost comparison for a client, comparing
the various heat sources and found heat pumps were
by far the best value for money in the long term when
compared to pellet boilers, electricity, and LPG gas.
Solar is still tricky to use as a heat source on its own, as
there is no way to store the energy and you need the energy
at night when the sun doesn’t shine, explains Schröder. “The
main duty cycle of an underfloor heating system is at night
when the solar system is non-collective.”
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