Heating and Ventilating

Mike Lamb looks at precast panels and their application in underfloor heating
Structural conditioning is a concept that has been developed from the science of underfloor heating theory, using unseen pipework to provide buildings with a heating or cooling system depending on the time of year.

Coils of pipe are embedded within a concrete structure, a development within commercial buildings that first started to grow in popularity in the early 1990s. These concrete slabs are subsequently fixed into the floor, wall or ceiling of each storey of a building to provide thermal comfort, reduce energy use and offer a cost-effective alternative to conventional air conditioning.

With modern buildings constructed to such high specifications, the actual heating load is more often than not offset by internal gains, with heat energy being created through lighting, solar, computers and people, even in severe winter conditions. All these factors combine to result in a net seasonal cooling requirement.

Originally the air conditioning concept was seen as the only way to cool air in a building, however this is beginning to change. Such systems are damaging to the environment - fluorocarbons are used to cool the air before circulation - and require huge amounts of energy to run efficiently. This is extremely costly in light of the Office for Budget Responsibility's prediction that household energy prices will rise 7% this year and a further 3% the year after.

Gaining ground
The history of precast concrete floors dates back nearly 50 years but, in the wake of the alterations to Parts E and L of the Building Regulations, they have grown in popularity in recent years. The Part E requirement to reduce impact and airborne noise was a particular catalyst.

Noise nuisance is the single most common complaint in multi-residential developments and this greater mass of concrete absorbs noise dramatically, giving huge reductions in the impact sound. Other disadvantages of timber floors, such as creaking boards are also avoided.

Acoustic performance is far from being the only benefit of precast concrete floors.
They are more cost effective than timber and enable thinner floor zones as well as longer spans. In addition, they provide a safe working platform for ongoing construction. Critically, as discussed above, the introduction of large heat absorbing mass in the structure of a modern house reduces temperature fluctuations by acting as a heat store.

Not only does this make the house more comfortable, it also reduces the reliance on air conditioning and reduces costs for homeowners.

Added to this is the intrinsic fire resistance, an important consideration for a modern home littered with potential fire hazards, as well as its compatibility with other precast concrete components, such as stairs and balconies.

Another more obvious advantage for concrete floors is the ability to vary room layout without worrying about floor loadings. This feature applies equally at first-floor level, avoiding the concern about the positions of supporting walls. A heavy duty first floor ties the masonry structure together, making the total framework and the house much more solid. Concrete is not susceptible to wet/dry rot and woodworm.

Furthermore, masonry does not shrink to the same extent as timber drying out. This means that gaps under skirtings, cracks to block walls and door openings out of square will become a thing of the past.

A perfect match
Concrete floors are the preferable option when using an underfloor heating system. Heating pipes are traditionally placed in a concrete screed, thus offering the highest thermal capacity and maximising uniform heat transfer.

Warmafloor and Creagh Concrete have joined forces to take this once step further with the launch of SpanTherm, helping to contribute towards the Code for Sustainable Homes.

This is a pre-insulated precast concrete flooring system designed specifically for residential and mid-sized commercial ground floors.

It heralds a new and innovative approach to residential ground floor construction. SpanTherm is designed, manufactured, delivered and installed to site in a quick and safe way; leaving a structural sound and safe sub-floor that is ready to be built on in as little as one day.

This quick turnaround not only simplifies health and safety management but also reduces the time and material required for scaffolding.

The insulation thickness on the SpanTherm unit is greater than that used in the majority of systems ensuring that the floor exceeds current U-value requirements (0.25W/m²K) for ground floor construction.

The design has been developed in anticipation of the new building regulations.
The overall depth of the slab can be allowed for in construction of footing block-work levels. Underfloor heating pipes are incorporated in the top element of the unit.

Concrete provides thermal mass, retaining heat and keeping the floor warmer for longer. It naturally radiates the heat upwards as the polystyrene underneath acts as an insulation barrier to keep the heat retained within the slab.

// The author is managing director at Warmafloor //