Building Regs Part L changes – what does it mean for underfloor heating?

On 13th September 2005, the approved drafts for Building Regulations, Part L, Conservation of Fuel and Power and Part F, Ventilation were published.

The changes are due to come into effect on 6th April 2006 and correspond with the Government’s target of reducing UK carbon dioxide emissions by 20% in 2010. Bill McConnell, Technical Director of Continental Underfloor Heating considers how the installation of underfloor heating complies with the new regulations and helps to reduce carbon emissions.

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. 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.

Previously, the 2002 Part L regulations gave installers three alternative routes to compliance. These routes were all connected to the measurement of U-Values. U-Values are a calculation of energy efficiency used to rate and compare windows, exterior doors, skylights and other building components. They are the industry standard adopted in the building codes for specifying the minimum and maximum energy values for all the components. The three previous routes to compliance were as follows:

1) Elemental U Values – each element within the building is individually calculated to achieve a set value.

2) Target U Values – the ‘trade off’ method where, for example, a higher U-value on one element could be traded off against a lower U-value on another element.

3) SAP Ratings – Compliance could be achieved through the Government’s Standard Assessment Procedure for Energy Rating of Dwellings.

Under the new Part L regulations, these three existing options will be removed and replaced by a ‘Target Carbon Dioxide Emissions Rating’ (TER). This is a calculation of the carbon dioxide emissions resulting from the energy consumption of the building as a whole. Now, the only method of complying with the energy requirements of Part L will be to calculate the emissions of the house using Government ‘SAP’ software and ensure the emissions level is no higher than the TER. The changes should give installers considerable freedom in the specification of individual components, so long as the overall emissions target is met.

So, how do changes to regulations affect underfloor heating? How can installing underfloor heating help to reduce a building’s overall carbon emission rating? In theory, underfloor heating combined with a gas boiler is treated no differently to a radiator system when calculating carbon dioxide emissions. However, in practise there is a difference as underfloor heating is designed to run at lower temperatures than a radiator system.

In general, the lower the return temperature of water onto the boiler, the more environmentally friendly the boiler will be, with fewer carbon emissions. Traditionally, radiator heating systems have a water flow temperature of 82ºC and a return of 71ºC. This has kept the return temperature high and above condensing temperature.

Underfloor heating on the other hand typically has a flow temperature of 50ºC with a return temperature of 43ºC. This is well within the condensing range of a modern gas boiler, which ultimately results in a reduction of green house gases and makes the entire system more environmentally friendly. To summarise, underfloor heating keeps the return temperature of the water onto the boiler at a more suitable condensing range and therefore ensures a far more efficient use of fuel than a traditional radiator system.

As well as the benefits linked to condensing boilers, underfloor heating can also help to reduce carbon emissions when installed with alternative heat sources. It is estimated that 30,000 homes are built every year where there is no mains gas supply. In this situation, there is a choice between oil or solid fuel boilers, electric heating and heat pumps. However, the new regulations do not rate electric systems favourably. An obvious alternative for these houses is the use of a ground source heat pump, which used in combination with underfloor heating, conforms to the new regulations.

The heat pumps generally supply a maximum water flow temperature of 45°C to 50°C, which is an ideal temperature for underfloor heating 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 underfloor heating system and choice of floor finishes. The more insulative the floor finish, the higher the flow temperature required by the underfloor heating.

The new building regulations will force plumbers, builders and installers to consider different methods of achieving, and if possible, exceeding the targets of the new regulations. As this article demonstrates, underfloor heating in combination with modern condensing boilers or alternative heat sources is well positioned to help achieve these targets.

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


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