Your top ventilation questions answered
Jaga’s Technical Consultant Andy Williams provides building specifiers with his insights on the various ventilation solutions for buildings, including how they can be monitored, managed and maintained.
How can air quality be monitored, and how has this changed over time?
In the twentieth century, pollution was detected in locations such as mines by placing canaries in each mining pit, as they are incredibly sensitive to toxic gases. Any sign of distress displayed by the canary would signal that the conditions were unsafe, and miners were evacuated. In recent times, this method has been replaced by electronic sensors, which are able to detect whether the air in buildings is rich in particular gases. It is widely accepted that in occupied spaces, CO2 levels are one of the best indicators of air quality, and this is easily monitored.
Can you explain the different ways that Indoor Air Quality (IAQ) can be managed?
IAQ can be effectively managed if a building is properly ventilated. The three main types of ventilation for buildings are:
1. Natural ventilation – this requires no moving parts, and instead relies on the differences in pressure, wind and temperature within a space. Opening a window on either side of a building would be considered natural ventilation – allowing the air to move from the outside into the room, and from the room to the outside.
2. Mechanical ventilation – this requires the movement of a fan, which can effectively force air in, and then out of a building.
3. Hybrid ventilation – this is a combination of mechanical ventilation, and natural ventilation. An example of this would be if a mechanical inlet was used to force air in – creating a positive pressure in the room – before forcing air out naturally through an open window, or vice versa. Alternatively, the use of a natural ventilation system as the primary method with a mechanical ventilation system used as a top up would also be considered a form of hybrid ventilation. This is becoming a common solution for schools, and in the final draft of the amended Building Bulletin 101 ‘Guidelines on ventilation, thermal comfort and indoor air quality in schools’, hybrid ventilation is discussed in more detail.
What is Demand Controlled Ventilation (DCV)?
DCV is a ventilation strategy which enables the careful monitoring of a space, whether that be ventilating through natural methods such as opening a window, through mechanical methods such as a fan, or a mixture of the two. DCV primarily is an automatic system that does what it needs to, when it needs to do it. A well-designed system would also allow the occupant to temporarily override the automation to purge the space, or even shut-down should noise level be an issue from external sources.
What is the impact of over ventilating a room?
If a room is over ventilated, it will mean that the IAQ of the building will nearly match the external air quality. Whilst that level of freshness is likely to ensure that productivity remains high, over ventilating can impact the bill payer. For instance, in the winter, the high volume of air being brought in will need to be heated to match the room temperature. This is one of the reasons why buildings such as schools should choose DCV – as this strategy only triggers the introduction of fresh, filtered air when necessary, instead of at a fixed rate.
Can you detail the maintenance required for a DCV mechanical ventilation solution?
The ventilation system:
Generally, a mechanical system will incorporate some level of filtration to clean any external air prior to introducing it into the room. These filters would need to be cleaned or replaced on a regular basis as part of a planned maintenance programme. This is particularly important if the air intake is close to a busy road or a highly polluted environment, and especially if the filtration uses chemical to remove gases too large to filter. Along with the filters, the operation of the ventilation units must be checked to ensure correct operation.
The control system:
Most control systems are designed and installed to a specification, which meet the needs at the time of design. As the use of the rooms change over time, it is important to ensure the control system is maintained, checked, and where necessary changed, to meet the demands of a space. This is often overlooked once a building has been occupied.
What are your predictions for ventilation in UK buildings?
Buildings are being built and retrofitted with energy efficiency in mind, and as a consequence are incredibly airtight, impacting the overall IAQ. I believe that offices and warehouse-based buildings in particular will experience a large uptake of smart ventilation solutions in the near future, as doing so can reduce the staleness of the air in buildings and improve productivity. There is a large focus on ventilation in educational buildings, but less so in other working environments. This will soon catch up.
For schools, what three qualities must a ventilation solution have?
1. Be discrete and not disruptive in any way
2. Functional – meaning it must meet the requirements of the school and regulatory standards
3. User-friendly – the system must be intuitive enough that end users can easily make any adaptions needed
Want to understand how the new Department for Education BB101 regulations will impact the design requirements of schools? Click here to register for our webinar on the topic.