Building services design in London

Fabric first: how insulation sets the size of the plant

A well-insulated house needs a smaller heating system, so the fabric figures come first. For a new dwelling, Approved Document L limits windows to 1.6 W/m²K, doors to 1.6 and rooflights to 2.2. Those are limiting values, so the design aims better than them.

Renovations follow different thresholds. When an existing roof is being replaced or substantially rebuilt, it must reach 0.16 W/m²K if it is currently worse than 0.35. Existing walls trigger an upgrade above 0.7 W/m²K when they are being altered.

We run the heat-loss figure from the model and use it to size the plant. A modest extension on a leaky Victorian house can change the answer for the whole building, which is why we look at the house and not only the new room.

Heat sources, hot water and the cylinder cupboard

The choice between a gas boiler, an air source heat pump or electric heating shapes the whole design. A heat pump asks for larger emitters and a cylinder, because the guidance caps its design flow temperature at 55 degrees Celsius. Fitting that into a London terrace is mostly a question of space, which is why we settle it on the plans.

Hot water has its own limit. Bath taps are to deliver no more than 48 degrees Celsius to prevent scalding, which in practice means a blending valve or similar control on the bathroom supply.

Water use is capped at design stage too. The calculated figure is 125 litres per person per day, falling to 110 where the optional requirement is imposed on the scheme. We choose the fittings from that budget and record the result for building control.

Air, power and connections

A sealed, insulated house must breathe on purpose. Approved Document F sets a whole-dwelling rate that rises with bedrooms, starting from 31 l/s for three and adding 6 l/s for each bedroom beyond five. Individual rooms have their own extract duty, such as 15 l/s for a bathroom.

On the electrical side, the later edition of Approved Document L raises the efficacy of fixed lighting to 105 lumens per circuit watt. A new dwelling with parking also needs a charge point of at least 7 kW, so the consumer unit and cable route are sized for it from the start.

Dates matter. The next editions of the energy and ventilation documents come into force on 2027-03-24, and we say in the design notes which edition each figure comes from.

What you receive and what it costs

The package is a services strategy note, a heat-loss summary, plant and riser locations drawn into the model, and coordination sheets showing services against structure. Where the project needs full layouts, the M&E and drainage sheets are added to the same set.

We do not publish a starting price. A single extension and a retrofit of a whole house are far apart, so we run a free constraints check, agree the scope with you and send a fixed quote. Specialist calculations outside our scope are named in the quote, with who covers them.

We design and draw. A qualified installer fits and certifies the systems, and the design gives them what they need to do it once.

Where the services stage sits in the project

We start when the plan layout is nearly agreed, because the services depend on it. A first coordination pass checks routes against beams and joists, and a short list of clashes goes back to the design team. Anything that needs a wall or ceiling to move is easier to change at this point than on site.

A second technologist then checks the services set, and a senior review signs it off before it joins the construction drawings issued to your builder. If the structure is being redesigned at the same time, our structural engineering work is coordinated against it in the same model.

Building services design across London councils

Local conditions decide how visible the plant can be. A flue or condenser on the front of a house in a conservation area meets more resistance than on a modern estate, and Article 4 directions can bring small external items under control. Our council pages show the designations that affect a house in each borough.

Start with the borough where the house stands. Architectural drawings in Hackney shows the format, and architectural drawings by area lists every place we cover.