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As businesses get ready to reopen their office buildings while keeping to social distancing measures, what might the impact be on energy efficiency in those buildings – and the climate emergency?
Before COVID-19, the climate emergency was very prominent in the media, and the UK was the first major country to commit to achieving zero carbon targets by 2050. With the current pandemic, however, the focus on buildings is moving away from energy efficient buildings, and towards healthy buildings. But can we have both?
The Chartered Institution of Building Services Engineers (CIBSE) has just released a set of documents which provide guidance for building owners and managers on how to start reoccupying their buildings. The guidance relates to safe working practices and the assessment of building services.
Some of the key themes are around air: providing more fresh air and avoiding recirculating air. The guidance includes bypassing those heat recovery devices which may recirculate air in some circumstances, and considering air pathways – how air comes in, moves around and leaves a building. This is because occupants of a poorly ventilated room are exposed to a higher concentration of airborne pathogens. The risk of exposure increases with the time spent in such an environment.
Suddenly, wellbeing and temperature control are higher on the priority list than energy efficiency and the climate emergency.
Normally, having fewer people in a building would allow ventilation rates to be reduced, making a building more energy efficient. However, in order to reduce the risk of viral spread within the building we have to increase ventilation rates as far as practically possible, so that the occupants have more fresh air.
A higher ventilation rate, whether it is via natural or mechanical ventilation, will result in an increased demand on heating in cooler weather, and increased demand on cooling in warmer weather. This may be exacerbated in a mechanical ventilation system where we’ve had to disable the heat recovery device. Extra heating or cooling not only adds to our energy bills, but it also puts more pressure on hitting our carbon reduction targets.
In the short term, the UK will see more warmer weather as we head from spring into summer. Opening windows in naturally ventilated buildings is accepted behaviour on warm days. But now it’s important to open the windows before people start to come into the building, and to let the building air at the end of the working day. Longer office hours – in order to enable social distancing – will mean windows are typically open in the early morning. Heating systems will battle to heat buildings in the cool mornings, as the heat escapes out of open windows.
Unless we think carefully about our heating controls, heating bills could well go through the roof.
But building occupiers will also need to balance the need to open the windows with safety security concerns, especially when there are periods of low or no occupancy. People on ground floors in largely empty offices may feel particularly vulnerable to intruders, for example. And open windows or doors may pose a health and safety risk if there’s a chance people will walk into them.
There’s an equally complicated scenario for mechanically ventilated buildings. With heat recovery devices switched off and air flows turned up to the maximum, buildings will struggle to warm up in the early morning. Once a building is up to temperature it may well overheat as the ‘coolth’ normally recovered from an office is being thrown away. In summer, this means chillers will be operating at maximum capacity (often less efficient), and they may not be able to deliver the total cooling required.
To make the problem worse still, it’s recommended that recirculating cooling systems (fan coil units or passive chilled beams) are switched off in rooms that have limited fresh air, to limit the movement of airborne particles. This would mean no comfort cooling in spaces such as offices in peak summer. And although this will give great energy savings, the wellbeing of occupants will suffer as rooms overheat.
Keeping heat gains down in summer will help reduce the cooling load of the building, and give the cooling systems a fighting chance of keeping us at a comfortable temperature. Social distancing measures will help reduce internal heat gain, as there will be fewer people using fewer computers in each office. Blinds on the windows can help to reduce heat gain from the sun. And making sure that the lighting controls are working properly can reduce the lighting load (which also creates heat) during bright days.
Desk fans help to reduce the perceived temperature by around 2oC, but the additional air movement increases the risk of particle movement. So desk fans are not recommended, except in rooms with good airflow and high air changes. A simple, but effective, approach might well be just to have a relaxed dress code. That way, people can dress according to how warm they feel, which will make them more comfortable, and more productive as a result.
Our dynamic thermal simulation enables a data-driven approach which we can use to predict internal temperatures, air flow and occupant comfort in existing offices. It allows us to model scenarios so that building operators can effectively predict threats to occupant comfort. We can test rectification measures in a simulated environment and understand how they will affect energy bills – before choosing the most appropriate option.
Once you have planned how to meet the challenges of thermal comfort, now is also the time to do a full MOT of your ventilation, heating and cooling plant. Cleaning out the filters, checking the pump pressure and tweaking the control systems are all examples of simple fixes that will help plant to run more efficiently and reduce energy bills. CIBSE provides recommendations on how to maintain ventilation plant safely, given the viral risk.
Over time, we adjust the ventilation in a building to suit the partitioning of spaces and changes to how the building is occupied. Now is a great time to check the commissioning of your systems to make sure there is a good spread of ventilation across each room.
It’s important to pay particular attention to toilets, and transient spaces such as stair cores. With social distancing, a 20-person lift is now only able to carry one person, so staircases are going to become much busier. These spaces need adequate ventilation, therefore. They shouldn’t be overlooked just because people don’t spend a large portion of their day sitting in them. This might well present its own challenges.
The government recommends that all building owners and occupiers undertake a COVID-19 risk assessment before moving back into their office buildings. The health and safety of occupants is of paramount importance. But this moment also gives you an opportunity to make small changes to the way your systems operate; to make meaningful improvements to the efficiency of systems, control your energy bills and limit the impact of increased ventilation on the environment.