Heating bills at the Thai Embassy
Built around 1770, the Office of the Commercial Attaché of the Royal Thai Embassy in London’s Mayfair is a handsome, Grade II listed townhouse in the typical Georgian style. Until very recently, it was heated by an old non-condensing gas boiler that was both inefficient and five times bigger than it needed to be to serve the needs of the building and its occupants. It was time for an eco-friendly upgrade that would cut the Embassy’s excessively high gas bills without impacting any of the historic property’s architectural features.
Right-sized solution
When the project was put out to tender, London-based central heating and boiler replacement specialist Boilertrust, which carried out the retrofit, was the only company to suggest a domestic boiler. Company director James Pemberton explains, “Our niche in London is Mayfair townhouses like this one where a complete renovation to improve insulation isn’t feasible. Many of these old properties have a commercial boiler but don’t actually need it. Switching to a domestic solution is easy, it’s just a case of getting people in who have the confidence and knowledge to do it properly.”
The experienced Boilertrust team led by Andrew Millward, senior instructor and lead engineer, specified Viessmann’s exceptionally efficient, wall-mounted Vitodens 200-W gas condensing boiler with a 32 kW rated heating output, paired with hydraulic separation via a plate and weather compensation controls. As well as being durable and low-maintenance, the Vitodens 200-W has Lambda Pro Plus combustion control which ensures maximum efficiency at all times and automatically adjusts for fluctuations in the gas supply or wind effect on the flue, making it a sound, future-ready investment.
The old heating system pipework was open-vented and this feature was retained in order to avoid any complications with cisterns or joints that might not be able to withstand the pressure of a sealed system. A pump was used to dispose of the condensate from the new appliance, as the basement plantroom lacked access to a drain.
The new system is split into several zones across the building’s five floors. Because the pre-existing boiler controls were retained at the client’s request, a relay box is used to allow the boiler to come on in its weather compensated mode whenever any of the zones request heat.
“This approach did mean the project took more time and cost slightly more than if we had designed the system ourselves from scratch,” says James, “But we were able to accommodate the customer’s needs with the Viessmann system.”
Despite this additional complication, the entire job was finished within four days in October 2023, in time for an important reception taking place at the property the day after its completion.
Boiler versus heat pump
Before opting for the Vitodens 200-W, the client and Boilertrust did consider a heat pump solution. This approach was quickly ruled out, however, because, with neighbours on either side of the terraced property, its listed status ruling out installing anything at the front, and insufficient space at the back, there was no suitable location for the outdoor unit.
“These are typical concerns in London – boundaries, neighbours, aesthetics,” James observes. “This is an important case study because it shows what you can do in buildings that have substantial challenges for a heat pump. The range-rated Vitodens 200-W is effectively operating as a heat pump, but with the ability to produce exceptionally hot radiators should the client require in very cold weather, as is the case for many older, listed buildings where property improvements are very difficult to implement.”
Impressive savings
With the new system, the building’s heating bills are forecast to plummet up to an estimated 50%, equating to savings in the thousands per year. “These projections go to show, you can achieve dramatic reductions in energy bills by using weather compensation correctly installed with a Viessmann natural gas boiler,” adds James. “I’ve no doubt that heat pump technology will become more and more tailored to housing types that it isn’t currently working for, but in the meantime, this is something that can be done to dramatically cut bills and carbon now.”
Before & After
System Specification
Weather compensation controls