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Service Ducts

June ’12

The close grouping of services and the placing of them in a fairly centrally situated service duct, usually a duct which extends vertically through the house, has a great deal to recommend it but is seldom executed well.

The schematic above shows a simplified services layout with a service duct which houses a class 1 flue, a cold rising main, hot water pipes, central heating pipes, electric runs, air extract and supply, gas supply, soil/waste and telecoms. To this might be added thermostat wiring, PV wiring, security wiring, air supply to stove and home automation. (although some of these might be wi-fi) and probably sprinkler pipework in Wales. All of these may need repairing, modifying or extending over a period of years so it pays to have them accessible.

If a composting toilet is being incorporated into the design then this is an ideal place for the drop tube. Also centralised vacuum cleaning pipework and aerial wiring can go in. Of course it will probably make sense to design the staircase next to the vertical duct and if a lift should happen to be incorporated then it may work well to have it next to the duct.

Incorporating such a duct provides several advantages

  • reduced amounts of materials used for service runs – hence lower cost
  • less heat lost in pipework
  • less pumping energy needed for central heating (the resistance in pipework is inversely proportional to the fifth power! of the diameter of the pipe)
  • easier integration with solar power later on (solar ready)
  • easier access for repair and modification

There are a couple of potential problems with such service ducts

  • They need to be carefully sealed where they go through the external fabric of the building to prevent cold air infiltration (and also to prevent vermin entering)
  • Such close grouping of water and electrics needs careful planning so that possible leaks cannot cause electrical problems or danger with gas.

It usually works well to place such a duct centrally on a North facing wall since bathrooms will tend to be on this side. It may be possible to incorporate meter cupboards into the same wall at the base of the duct. Maintenance access to items such as a boiler and MVHR fan unit should be considered.

In the case of Passivhaus or Enerphit where MVHR is incorporated then it may be a good place to house the MVHR unit. This will depend on the way the air flow through the house is designed and the relationship of the service duct to the outside of the house. See Ventilation.

Skirting ducting can be utilized for most types of cable and is very easy to design in on horizontal runs until you come to a door way. Getting round doors is not easy and there is no simple equivalent type of architrave for ducting cables. Such ducts are not forced to make it look like you are in an office. Various domestic versions are available and it is a simple matter for a joiner to run up timber sections which will create a duct and look quite traditional. These can easily handle cat5 cable and normal electrical cable such as 2.5mm T&E.

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