The obvious choice if renovating a building is surely to move to more sustainable alternatives. The drive for decarbonisation is pushing a fabric-first agenda and a move toward electric systems, heat pumps and solar. This is baked into legislation for new build projects but retrofit of existing properties, where natural gas remains the dominant energy source, creates regulatory tensions as building owner/operators try to address health, safety, technical and cost constraints over sustainability gains.
Accommodating sustainable applications comes with a whole new set of challenges and costs. Accurate load calculations, considering occupancy patterns and usage habits, are crucial for optimal system sizing. Electric heating elements, or systems using heat pumps for low carbon preheat, take longer to reheat water; this slower recovery rate demands an increase in the storage volume, demanding extra space. This can be mitigated with high-temperature heat pumps, but this introduces other issues, such as shoring up the roof for these much larger and heavier units, and wider safety concerns over fire from the use of propane refrigerants when associated with solar PV installations. Resultant building works and fabric-first alterations can also reveal hidden issues, such as asbestos in older buildings. The alternative is to raise the kW rating of the electric heater to meet peak demands, which not only has operating cost implications but may clash with the existing electrical capacity of the building, especially if renovation projects incorporate other electrical services, such as EV charging. Resultant upgrades to the building's electrical supply, which can include extensive and extremely costly groundworks out to the nearest grid substation, can easily hinder or even stall projects entirely.
Because of this, gas water heating remains relevant for supporting existing buildings on the path to a transition to zero-emission operations. Familiar and well understood, gas water heaters remain low-cost to purchase (which will be allowed until 2035) require little change to the building fabric, and running costs are still considerably lower than electricity. However, there remains the stumbling block of the variety of ageing appliances in buildings, limiting the choice of replacement and often forcing the use of the same outdated technology if extensive building work is to be avoided.
Addressing this requires gas water heaters, which can match or better still reduce the footprint in the plantroom of older systems. Critically, new appliances need to be able to support universal connectivity, directly aligning with, or requiring little additional work to connect to existing pipework. Versatile flueing is also a necessity when supporting universal retrofit of older systems. This delivers minimal to no impact on building fabric or change in space requirements, even if converting to high-efficiency gas.
As well as ease of installation, operational functionality and system durability are key. The latter is especially true in soft water regions where the corrosive nature of local water can greatly limit the choice to systems typically constructed of more durable, but expensive, stainless steel. However, the use of high-quality steel and double porcelain coating techniques means this is no longer the case. The application of advanced power anodes also helps to greatly minimise wear to extend a water heater’s life in soft water conditions.
The advances in appliance design, diagnostics and onboard monitoring are also helping reshape the approach to gas water heating. Operationally, next generation gas water heaters must meet high thermal efficiency, where as much as 98% is readily achievable, reducing energy demands and therefore operation costs. This, when coupled with condensing technology, the capability to use natural gas/hydrogen blends and intelligent monitoring, helps control emission levels wherever possible. Diagnostics also allow for proactive monitoring of the systematic health of the tank by providing alerts and maintenance reminders, all of which can be integrated into the building management systems (BMS). Wi-Fi connection also opens options for app-based remote control and smart energy use monitoring. With onboard metering, estate managers and operators can better manage energy demands as well as detect and deal with problems before they become critical, ensuring their business is not penalised with any downtime.
Given the higher current CAPEX and OPEX of heat pumps, gas remains a viable alternative for commercial water heating for many commercial sites. Whilst not contributing as strongly to decarbonisation goals, gains can still be made, operators wishing to introduce a greater degree of sustainability can still lower costs and emissions by adopting a hybrid strategy. This involves keeping a smaller gas-fired unit for ‘peak lopping’ while a smaller heat pump manages the base load throughout the day. This typically avoids electrical upgrades and lowers initial investment while still cutting carbon emissions by as much as 60%. Further reduction in both operational costs and emissions is also attainable for both gas and heat pump systems if solar thermal is introduced as a truly renewable system pre-heat, or mid-heat source. This makes the eventual transition to all electric, heat networks or green gas alternatives more financially viable between 2035 and 2050.
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