Underfloor Heating and Part L regulations

Bill McConnel, Technical Director of Continental Underfloor Heating considers how the installation of UFH can help builders to comply with the new regulations.

The approved drafts for the Building Regulations, Part L, Conservation of Fuel and Power and Part F, Ventilation are published.

Part L of the new regulations looks specifically at conserving fuel and power, reducing heat loss, improving energy efficiency standards, providing better insulation and ensuring more efficient heating systems in buildings.

Bill McConnel, Technical Director of Continental Underfloor Heating(UFH) discusses how this change in legislation will require builders to rethink their design ideas and considers how the installation of UFH can help to comply with the new regulations.

The changes correspond with the Government's target of reducing UK carbon dioxide emissions by 20% in 2010 and are due to come into effect on 6th April 2006.

The Office of the Deputy Prime Minister suggests that the proposed changes will save around one million tonnes of carbon per year by 2010.

Currently, buildings account for 45% of the total use of energy within the UK and this is obviously reflected in carbon emissions.

Not only will the proposed changes help to improve energy efficiency within the home, it is also proposed that new homes will see a 40% decrease in their domestic fuel bills.

Principally, this article will consider ADL2A - a document intended to give guidance in relation to works comprising: a) The construction of new buildings other than dwellings; b) Where it is deferred for any reason, the first fit-out works in buildings that were built to comply with Part L as amended in 2006.

c) The construction of extensions to existing buildings where the gross floor area of the extension is greater than 100m 2 and greater than 25% of the gross floor area of the existing building.

The regulation requires a reduction of 20% in energy use for air-conditioned buildings and a reduction of 15% for naturally ventilated buildings.

Additionally, the regulation stipulates that if possible 10% of the energy use should be derived from renewable energy sources.

The changes to regulation will have significant effects on both builders and the end user.

The approach to building design will be fundamental, with energy saving technologies being integrated into the building at a much earlier stage of the design process.

The end user will also be required to conduct energy efficiency monitoring.

The construction of the building will also be tightened to improve energy efficiency, with lower U-values required on all building elements, set targets for air leakage and a reduction in cold bridges (areas in the building where a gap occurs in the insulation).

So how can the installation of UFH help in complying with the new regulations? UFH runs typically at a maximum temperature of 50 degrees C and sometimes as low as 35 degrees.

The flow temperature is largely dependent on the floor construction, pipe spacings, water flow rate, heat output required and the type of floor finish.

Condensing boilers and alternative heat sources such as geothermal heat pumps, both work best at lower water flow temperatures and are therefore suitable for use in combination with UFH.

The low flow temperature of UFH (approximately 35 degrees C) can allow a boiler to operate at a 98% efficiency rate, opposed to only 88% when being used in conjunction with a higher flow temperature system, such as radiators.

When UFH is being installed, one of the key considerations will be deciding whether to control the temperature of the UFH water locally (at each manifold) or centrally.

Central control is justified when the thermal resistance of the floor finishes are similar throughout the building.

Central temperature control has several advantages: The temperature of the water is kept to a minimum, making full use of the condensing abilities of the boiler Distribution pipework temperatures are lower and therefore pipework heat loss will be reduced.

Only one centralised speed controlled pump set is required, opposed to having a centralised pump, plus satellite pumps on each manifold.

This can further help to save energy and reduce capital cost.

UFH also emits a greater percentage of its heat as 'radiant heat' opposed to 'convective heat'.

This too can make a difference, as people tend to feel comfortable at lower air temperatures with a radiant heat source than they do when the air is being solely heated convectively.

In practical terms, this is likely to mean that the end user would reduce the temperature required of their system by 1.0 to 1.5 degrees, further improving overall energy efficiency.

With the Government's drive to actively encourage the use of renewable energy sources in new buildings, UFH clearly has benefits.

Heat pumps generally supply a maximum water flow temperature of 45C to 50C, which is an ideal temperature for UFH to operate effectively.

With this range of flow temperature, the COP (Coefficient of Performance) of the heat pump would be around three.

This means that for each kilowatt of electrical energy put into the heat pump, three kilowatts of useful heat should be produced.

This figure can be increased with careful design of the UFH system and choice of floor finishes.

The more insulative the floor finish, the higher the flow temperature required by the UFH.

The new building regulations will force builders to consider different methods of achieving, and if possible, exceeding the targets of the new regulations.

As this article demonstrates, UFH in combination with modern condensing boilers or alternative heat sources is well positioned to help achieve these targets.

Continental UFH offers the most comprehensive range of UFH systems in the UK and has an expert technical team on hand to provide customer advice.

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