Decarbonization of humidification in commercial buildings

We’ve recently seen many clients replace gas-fired humidifiers with electric steam humidifiers because they can be powered by renewable energy, reducing overall carbon emissions. The retrofit is a relatively simple swap, as the same space within the AHU is typically required. In many cases, the existing steam distribution system can remain in place, reducing installation costs and complexity.

However, because gas-fired humidifiers can provide high outputs from a single unit, an electric steam system will likely require a larger overall footprint than the gas unit it replaces. This should be considered during project planning. Replacing a 320 kg/h gas humidifier may require three or four electric humidifiers to achieve the same output. Fortunately, humidification systems of this size are often installed on rooftops, which can help alleviate space constraints.

If plant room space is limited, or if the available electrical capacity is insufficient to support an electric steam system, adiabatic humidifiers may provide a practical alternative. Cold water humidifiers installed inside the AHU can deliver high outputs but require pre-heating before the humidification section. The entering air conditions must be dry enough to absorb moisture from the humidifier. This pre-heating is typically provided by a heating coil connected to a gas boiler.

Unfortunately, this approach does not support carbon reduction goals, as the overall energy consumption and carbon emissions in this scenario would be comparable to those of the gas-fired humidifier being replaced.

Rather than humidifying and cooling the incoming airstream, an EAEC system cools the extract air from a room using an evaporative humidifier. Return air conditions are relatively stable and can be humidified close to saturation to achieve the maximum possible cooling effect. This cool, saturated return air is then passed through a heat exchanger before being exhausted outdoors. The heat exchanger transfers the cooling energy to the incoming airstream, reducing its temperature by up to 10K.

Because the humidity increase occurs only in the return air, there is no impact on indoor humidity levels. The efficiency of an EAEC system depends on the performance of the heat exchanger, but even with a modest 70% heat exchanger efficiency, a typical building in London could reduce its reliance on mechanical cooling by approximately 40% using this strategy. While it is not a universal solution, EAEC provides real and achievable benefits for energy reduction and decarbonization initiatives.

Decarbonization is being driven by regulatory requirements and financial risk. Upgrading heating, cooling, and humidification systems will soon become essential for building owners and landlords, as failure to meet Minimum Energy Efficiency Standards could prevent a building from being legally leased. With many properties requiring upgrades, competition for skilled labor and building materials is likely to increase as deadlines approach.

Early planning can help avoid regulatory penalties and lost rental revenue. Condair provides free, expert guidance for building operators and facility managers exploring humidification and evaporative cooling solutions to help achieve or exceed the EPC B rating before the deadline.