Underfloor heating
Simple steps UFH installations made easy
Underfloor heating (UFH) is an affordable solution for many buildings and, as Nigel Sanger explains, installing a UFH system in a screeded floor is both easy and cost-effective
UNDERFLOOR HEATING pro- vides a comfortable, even warmth to compete with any heating sys- tem and the long-term running costs are lower than any radiator- based alternative.
UFH matches the preferred room heating profile, which con- centrates maximum heat at floor level, a slightly lower heat at head height, with the lowest tempera- tures at ceiling height. This is the precise opposite to conventional radiator or warm air systems, which see hot air rising wastefully to ceiling level. With UFH, there are no cold spots or hot ceilings. For the installer, UFH allows pipework to be installed, filled and tested in one operation. The system consists of a manifold, which distributes the heating water to each UFH circuit and allows the isolation and flow rate setting of each; a control pack connected to the manifold to reg- ulate the flow temperature and pump water to each circuit; barri- er pipe, a pipe fixing system and a heating control system.
Maintenance requirements are minimal as there are few moving parts within the system and pres- sure testing is carried out before installation. What follows is a step- by-step method to a trouble-free installation:
1. Preparation With a solid floor, it is essential to ensure sufficient floor depth is available and suitable insulation specified. Insulation depth is determined by design or building regulations which require that any downward heat loss does not exceed 10 watts per m² in accor- dance with BSEN1264. When installing the system, special con- sideration should be paid to areas of high heat loss which may affect the performance of the system.
2. Preparing the floors
Floor insulation should be fitted to a flat sub-base and joints securely taped over. An expansion strip is required around the perimeter of the room to accommodate the expansion which will occur within
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the screeded area as the system heats up. BX EN 1264 Part 4 requires a protective membrane to be placed over the insulation layer to prevent contamination of the insulation by the screed.
3. Choosing the pipe layout There are several ways to lay pipe, depending on pipe spacing, room layout and fixing method. Serpentine is a simple up and down circuit pattern, especially suited to irregularly shaped rooms or small areas such as kitchens and utilities. Counterflow, or spiral, pat- tern achieves an even floor tem- perature with alternating flow and returns, with a typical pipe spacing of 200mm. Both can be combined to suit the shape of the room and
in rooms requiring multiple circuit areas, counterflow and serpentine can be used to good effect.
4. The manifold and pump pack The manifold consists of two rails, one for the flow and one for the return, complete with ball valves and drain/filling valves. Some manifolds, such as JG Speedfit’s, are supplied complete with pre-fit- ted brackets and vibration isola- tion mounts. The manifold is fitted to the wall, allowing enough height to accommodate the insula- tion and screed depth, pipework and conduit elbows. Pipework is then connected to the manifold and run to the room to be heated. If it passes through other rooms, use conduit to prevent the
Step 1 Step 2
pipework influencing heat in those rooms.
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5. Installing the pipe Using the screed as a heat diffuser, you can choose between a staple system and a mounting rail for pipe installation. Staples should be attached at approximately 500mm apart and a gauge will keep the designed pipe centres even and help the installation process. Mounting rail, especially suitable for large regular shaped areas, pro- vides ready-made pipe spacing and can be fixed to insulation which is too thin for staples. In either case, begin by connecting the pipe to the manifold and start the first cir- cuit 75mm from the perimeter.
6. Filling and testing Step 6 Step 7
Ensure the water is forced around the UFH loops one at a time to prevent short circuiting from one manifold rail to the other. If there is the possibility of freezing condi- tions, suitable antifreeze should be added to protect the pipework. Once the system has been filled, a hydraulic pressure test should be carried out on all loops in the sys- tem.
7. Applying the screed
The screed should be laid as soon as possible after the pressure test and the system should be left under pressure during screeding. Low thickness pumped screeds are available and work well with UFH. Screed drying times will vary, typically 28 days for a sand/cement screed and UFH sys- tems should never be used to speed up the drying process.
8. Start-up and commissioning Following the manufacturer’s instructions for start-up, the initial water flow temperature on screed- ed floors should be maintained at 25°C for three days. On day four, it can be increased gradually in increments of 5°C per day until the maximum design temperature is reached. This must then be maintained for a further four days. • Nigel Sanger is the technical manager at JG Speedfit
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