Technical Director Andrew Grimsley Andrew Grimsley, Nu-Heat’s Technical Director looks at how underfloor heating has developed over the years into a flexible system with relevance to today’s energy efficiency demands.
The market
In the UK in the 1980s, underfloor heating (UFH) was a niche product for a limited market made up mainly of self-builders who had come across UFH on their travels around Northern Europe or at self-build exhibitions. Self-builders appreciated an unobtrusive heating system that offered comfort along with aesthetic freedom.
The main impediment to market growth was a lack of installers who were nervous of the unknown technology. Once they realised the potential of UFH - the relative simplicity of installation, good financial rewards and lack of competition - it was installers who drove the market forward.
The product
Improvements and developments over the years have usually been in line with major changes in installation standards. Where early UFH systems were mainly used with hand-laid screed or floating floors, Nu-Heat now has over 60 suitable floor constructions. Hand-laid screed is often now replaced with liquid screed, offering improved contact with the pipe and less air bubbles resulting in better conductivity and, consequently, heat output.
Fixing systems have stayed similar, although there have been enhancements such as ClippaPlate™, the brainchild of a member of Nu-Heat’s special projects team. This highly conductive aluminium plate is designed to speed up installation in suspended floors, provide a safer alternative to working over exposed joists and give improved heat transfer and response time.
The early pipe diameter was around 20mm, but the range now available includes 16mm and the 14mm used by Nu-Heat, enabling greater flexibility of installation. 10 mm pipe is often used in single zone installations. With proven performance in many decades of use in Europe, pipe construction - 5 layer PEX-C, aluminium cord PEX or polybutylene - has remained much the same.
The choice of floor covering has always had a bearing on the system design but Nu-Heat, for example, now specifies for most materials, including timber, tile, carpet and coir - although total tog values shouldn’t exceed 2.5.
Whereas original room controls were very basic, there are currently many controls available, from simple dial-type to wireless thermostats and sophisticated, low voltage, self-learning options with add-on Internet connections.
The future
The longevity of UFH is guaranteed by its relevance to the need for energy efficient systems. When UFH is partnered with a heat pump, its full potential to reach low running temperatures is reached.
The efficiency of ground source and air source heat pumps is intrinsically linked to the temperature of the water the heat pump has to produce. When UFH systems are specifically designed to be fed by a heat pump, additional tubing and more efficient floor constructions can be used to allow flow temperatures as low as 35°C whilst maintaining perfect comfort levels. This means that the heat pump can reach a Co-efficiency of Performance (CoP) of 4 – 5 – that’s 400 – 500% efficiency.
For any UFH installation, levels of insulation are essential to the efficiency of the system, but when a heat pump is to be used this is even more critical.
The retrofit
Liquid screed going over an installation The future for UFH also includes the growing retrofit market due to the need to improve existing buildings. Although not appropriate for every property, if there is sufficient insulation, good design and an experienced installer, UFH is a viable option. Floor, wall and loft insulation along with double glazed windows and doors will all help.
It is also vital to see if installation of heat pump technology is practical in a property. For example, an area approximately two and a half times the footprint of the property is needed for laying the ground loops for a ground source heat pump. If there is insufficient external space for ground loops or boreholes, an air source heat pump will provide a highly efficient alternative. Both types of heat pump require internal space to house the cylinder, buffer tank and other equipment.
The significant bit
‘Nu-Heat has supplied UFH for nearly 20 years and we believe that design is everything,’ says Grimsley. ‘Installers should look for a company that takes responsibility for the complete system.’
This is even more important when integrating underfloor with renewable technologies as the design must take into account the complicated heat loss calculations associated with lower temperature heating systems. A reputable company should supply bespoke mechanical and electrical drawings for all projects, including comprehensive installation manuals.
The flexibility of UFH as a system particularly when partnered with renewable products to create a low carbon renewable solution make it even more relevant to the coming decades than to the past!
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