Sports facility specifiers are under pressure to find energy-efficient heating. Anthony Waterman of Sense Cost Consultancy considers radiators vs underfloor heating for changing rooms
Energy costs are estimated to account for about 30% of the total operational expenditure of sports and leisure facilities. Most of this energy - up to 80% - is used for heating and hot water, and much of that is used in changing rooms and their showers.
Traditionally, the options for heating systems in changing rooms have been electric warm air heating or a conventional system of gas boiler and radiators. Electric warm air heating is no longer common given the dangers of electricity in wet areas. They also have a high running costs and a high repair cost - consequently (and my experience of playing Sunday league football confirms this) they often remain broken.
A radiator system is therefore more commonly specified. In particular, low-energy condensing boilers and heat pumps, because they operate at lower water temperatures than traditional systems and thereby provide energy and cost savings and improve the environmental performance in operation.
A radiator system is likely to be a low-temperature hot-water system piped from a central heat source to floor or wall-mounted radiators. Control would either be from a wall-mounted thermostat linked to control valve on pipework or thermostatic radiator valves. However, in order to use the low-energy benefits of condensing boilers, the radiators must be designed to suit water temperatures of 50°C rather than 75°C and have a perforated casing. The radiators will require regular painting (say every five years) and the pipework and so on will require servicing every year, along with an inspection of the boiler.
The case for underfloor heating
A viable alternative is underfloor heating, especially now that many of the faults that occurred in 1980s, when the system was first designed, no longer happen. By specifying underfloor heating one is able to keep the walls clear and the large floor area means that the water temperature can be reduced below that in a radiator-based system, thereby providing the required heat output for less energy. It also leads to improved comfort, thanks to warm feet and cool heads, and tends to keep floors dry.
Underfloor heating systems have a longer life expectancy and lower operating costs than they used to, and fewer repairs mean less requirement to remove the floor covering. In addition, plastic pipes are often used because of their ease of installation and repair, although copper pipes have better thermal characteristics.
When specifying heating systems for sports changing facilities one should assess the load requirements and likely peak use times and frequency for the facilities.
Given that changing facilities have intermittent occupancy one should consider how the specification of the heating system can cope with peaks and troughs in occupancy and take into account the considerable incidental heat gains contributed by teams of exhausted and dirty people.
Underfloor heating uses the floor area of a room as the heat emitter and has the advantage of saving space. Piped low-temperature hot water from central heat source supplies a manifold unit adjacent to the heated space.
Most makers propose expanded polystyrene as the insulating material, even though polyurethane has a lower thermal conductivity (0-021 W/m2K for polyurethane compared with 0-033 W/m²K for expanded polystyrene). Expanded polystyrene is cheaper and has better acoustic properties. The thickness of the insulating layer is generally 20-40 mm. Pipework is either buried in the solid floor or fixed within the suspended floor and linked to the manifold unit. Control valves located at each manifold allows for zonal control. Underfloor heating is suited for use with low-energy condensing boilers. Pipework and valves require servicing, and like the radiator system, this is assumed to take place every year.
The choice of floor type will affect the position of joints in the screed and therefore the positioning of the pipework. Flooring type is therefore a client briefing issue - not just for reasons of aesthetics, but also for reasons of system performance. One must also ensure that the floor area is free of shot-fired fixings as access for repair and maintenance is critical.
All reputable underfloor heating suppliers will provide detailed guidance on the application of their products, and the correct ways to interface those products with screeds and floor coverings.
Given that the underfloor heating system is embedded in the screed, it has the advantage of saving the cost of annual inspection, repair and painting of the radiators (assumed to be a five-year cycle). This results in a lower whole-life cost for the underfloor heating system despite a higher initial capital cost. It must be noted that the quality of installation of the pipework and the interface with the screed is critical because any failure of the system would mean that the screed would have to be dug up for to enable repair - this, more than likely, would negate any cost savings.
A specialist supplier and installer will carry out detailed design of the underfloor heating system. The standards that apply to the design (and installation) of underfloor heating installations include:
- BS EN 1264-1:1998 Floor heating – Systems and Components Part 1. Definitions and symbols
- BS EN 1264-2: 1998 Floor Heating – Systems and Components Part 2. Determinations of the thermal output
- BS EN 1264-3: 1998 Floor Heating – Systems and Components Part 3. Dimensioning
- DIN 4725, Part 4:1992 Hot Water Floor Heating Systems: Design and Construction (plus Amendment A1, December 1994)
- DIN 4725: 2001 – Floor Heating Systems and Components – Determination of Thermal Output, Pipe Coverings Larger than 0.065m
- BS EN 1264-4: 2001. Floor heating – Systems and components Part 4.
Notes for table: Three heating systems for use in sports facility changing rooms
Costs are for design, purchase and installation and maintenance of all systems. Assumed maintenance extra over costs includes annual inspection and maintenance of boilers; annual maintenance of radiators; five-year painting cycle for radiators. Prices are presented as £/item for two 20 m2 changing facilities. Expected service lives assumed are 15 years for boilers and radiators, 30 years for underfloor heating systems. Prices are average costs presented for indicative purposes only. A cost analysis based on project specific information is essential for a realistic best-value appraisal.