It should be noted that this requirement is for all above-ground pipework, and therefore would not be limited to just secondary (communal) distribution systems, as CP1 currently is. There is an additional requirement specifically for the communal distribution system.
Communal Distribution Heat Loss Target
In CP1 we saw the introduction of heat loss targets based on the number of dwellings within the building, and the amount of heat loss permissible across the system. This was set at a maximum permissible value of 100 W/dwelling.
In TS1 this maximum value has been split into 2 targets, one for design and one for in-use to allow a tolerance for inefficiencies caused during installation. The new targets are 75 W/dwelling at design, and 100 W/dwelling in commissioning/ operation.
There is also a new requirement for non-domestic connections, which brings these into scope of the standard where they were previously excluded under CP1.
This value is 1.66 W/kW connection at design stage, and 2.22 W/kW at commissioning/operation.
If these values are not met at design stage, further methods of reducing heat loss should be looked at, including:
• reducing operating temperatures,
• a more efficient pipework configuration, or
• a greater thickness of insulation or lower thermal conductivity of insulation.
In practice, this could be particularly challenging for any network operating above 55°C as thicknesses of insulation will become so large as to be impractical at higher temperatures, and the focus will primarily be on reducing flow temperatures.
It is important however to read these heat loss requirements in the context of clause 2/3.13.5 – that the heat loss from ancillary equipment will be considered (pipe supports, valves, flanges etc).
The method for calculating heat loss for these components can be found in BS EN ISO 12241: 2022. (Thermal insulation for building equipment and industrial installations. Calculation rules). However, there is an alternative option of applying a 20% allowance to the heat loss of the system to allow for these components.
If this 20% allowance is used, this will in practice reduce the 75 W/dwelling value to functional 63.5 W/dwelling at design stage.
It is expected due to the complexity of the calculation, that most projects will take the 20% allowance approach, only looking at the thermal performance of flanges/valves etc when they are struggling to meet the W/dwelling target.
It should be noted that the type of ancillary can have a big impact on the amount of heat loss, for example it would be typical when insulating a flange to leave sufficient space for the removal of the bolts. A system where the bolts would be removed vertically as opposed to horizontally would reduce the required space and could reduce heat loss by up to 60%.
Ancillary Equipment
Ancillary equipment is specifically considered in clause 2/3.13.8, where insulation specific for the component should be used, at the same thickness of as the adjacent insulation, where available. Where not available, well fitted insulation products should be used.
Where flexible mineral fibre insulation is used, the installed thickness of the insulation shall be assumed to be 75% of the nominal thickness, allowing for 25% compression of the mineral wool, unless it can be shown that the insulation is not being compressed.
What this means practically, is that the insulation thickness of flexible mineral wool insulation for these ancillary components will need to be increased, so that after the compression factor is considered, it is the same thickness as the adjacent insulation. For example, if the adjacent insulation is 80 mm thick, then the flexible mineral wool insulation would need to be at least 107 mm thickness.
Thermal Stores
For the first time TS1 brings thermal stores into the spotlight and has a set performance criteria against them. This new value based on average heat loss no greater than 22 W/m2 in its operating conditions. This equates to approximately 65-75 mm thickness of phenolic insulation (depending on vessel size and thermal conductivity) or 95-110 mm of mineral wool insulation (depending on vessel size and thermal conductivity). Figure 2 shows the performance criteria taken from the draft TS1 standard.
