Technology throws up many interesting solutions to improve energy efficiency and comfort levels within our homes, and although the utilisation of an under-floor heating system has its origins in antiquity, the modern versions are far more ethical and efficient.
Roman hypocaust systems may have provided luxurious environments for villa owners, but the high levels of smoke emitted and the moral implications of forcing slaves to operate them might make them a particularly controversial hot potato today.
There are two modern and vastly improved systems currently available for domestic use. One is an electrical installation; the other is a wet system.
Although the two may appear to be in competition with each other for the homeowner’s attention, in reality each can provide an ideal and unique solution to an individual property’s requirement.
It is, of course, important to consider whether either system will be suitable in the first place and that requires a basic understanding of how under-floor heating operates.
Under-floor heating systems are generally only suitable for ground floor installation.
In a wet system, hot water from the boiler is pumped around a network of narrow pipes that have been laid onto a base directly under the floor.
An electric system relies on a framework of heat emitting wires that are laid under the floor in a similar fashion to a wet system. There is also an alternative electrical system that can be laid on the floor surface with a thin covering placed over it.
In contrast to radiators and other heat emitters that heat a small surrounding area and rely on convection to distribute the heat, under-floor heating provides a cooler radiant heat over a larger area. This heats the space consistently over the floor’s entire surface, rising upwards to warm the room very effectively.
With a wet system, where the surface area of a radiator requires the boiler to heat water to around 80°C to produce an effective radiant heat, an under-floor system will only require a 45°C – 60°C boiler setting to provide a comfortable floor surface temperature of around 27°C. The savings in gas or electricity are evident.
Now this is fine, but because of this lower operating temperature, the insulation qualities of the property become more of an issue. Where insulation and other heat conserving measures are below standard, the effectiveness of the under-floor heating can be reduced to such a level that the benefits of installation can never be utilised.
The best way to avoid this predicament is to commission a specialist to undertake a heat loss calculation on the property and establish whether under-floor heating can deliver the expected or claimed efficiencies. Where the advantages are confirmed, then the design and installation of a dedicated system tailored to the specific requirements of the property should be considered.
Most of the above issues are overcome in new-build situations, and if gas is available, then a gas fuelled, wet under-floor heating system is probably the system of choice. The installation of the system into the floor as an incorporation of the build progression simplifies the procedures and makes for a durable and effective heating system. Coupled with this, new-builds provide the opportunity for well thought out design concepts that can include ground source heat pumps and solar heating devices to compliment the under-floor system and reduce operating costs further.
In these situations, under-floor heating can be installed as individual zone areas within the property, controlled by a central manifold with diverter valves operated by individual thermostats.
Once installed, wet system pipe-work is maintenance free and guaranteed for up to fifty years by some companies. However, precautions should be taken to avoid damage by frost should the property be empty for a considerable period, and care must be taken before drilling into a floor where an under-floor heating system is installed.
Where, because of location, a supply of natural gas is unavailable, LPG can be considered as an alternative.
The greatest problems with under-floor heating occur in retrofit situations.
Although gas fired wet systems might be the preferred option, the practicalities of installation are such that the use of electrical systems are the only feasible option. However even this can be problematic. Under floor heating requires insulation below the system to prevent the heat being absorbed by the ground or any conductive substance it comes into contact with.
The recommendations for installation on a concrete base are a minimum of 50 mm of foil backed insulation material, for example expanded polystyrene foam, Kingspan or Celotex. The heating coils, either wet or electrical are laid upon this, usually in a serpentine or snail configuration. Sometimes the system has a dedicated layer that fits on top and incorporates the minimum insulation layer. This is then covered with a sand and cement screed to a depth of 65 mm to 100 mm, or a liquid screed of 50 mm.
This requirement can often be quite impractical in a retrofit situation. The elevation of the floor required to install the system may be undesirable and the cost of digging up an existing floor may be prohibitive.
A final solution is the installation of electrical heating mats that can be laid under carpets.
Where any under-floor heating is installed, floor coverings like laminates, tiles and carpets should have a tog rating no greater than 1.5. A high tog rating will seriously affect the ability of the system to heat the air above it.
The installation of under-floor heating will deliver efficiencies in heating utilisation only if it is suitable for the property and correctly fitted. Recouping the installation costs may take many years, but there is no doubt that a professional installation will substantially increase the value and desirability of the property and can be a wise investment.
It is always essential to ensure that any heating installations or upgrades conform to the current specific building regulations.