I received some excellent questions during the Q&A section during the recent webinar that I presented. Here you can see my answers to these questions, slightly edited for clarity.
There is also a recording of the webinar available.
What does the SCA Guide recommend regarding the area of an AOV?
The required area of an AOV is 1.5m2 geometric area. Within the SCA guide there is now a new recommendation which says that if you have a CE marked ventilator according to EN 12101 Pt 2, then the ventilator can have a 1m2 aerodynamic area rather than a 1.5m2 free area. That will allow you to use a smaller certified ventilator than non-certified ventilator, perhaps a window and an actuator.
When using an evaporative cooling system, are there any controls regarding legionella?
Yes, obviously an evaporative cooler is governed by all the regulations in the UK regarding avoidance of legionella. Within the UK there is not a specific standard for evaporative coolers in terms of their hygiene. There is however a standard in Germany, from VDI, and a version of the Colt Coolstream unit is certified according to VDI. adds The certified version has some extra sophistication to the controls to make sure that the system is dried out more regularly and the water is changed a little bit more regularly to give you added comfort in terms of avoidance of legionella. Having said that, the standard unit is perfectly safe, it is just a question of whether you need the certification or not.
My colleague Paul Langford recently presented a webinar on evaporative cooling where he explained this area in much more detail. You can find his Q&A session here.
Do you have any information regarding fans located within the shaft and how these would be accessed and maintained?
Yes, in the presentation I showed fans being located on the roof rather than being located within the shaft itself. Generally if you want the system to be used for day-to-day ventilation it’s almost certain that you will need to mount the fans on the roof so that you have got room for either the environmental fan to be added or for the attenuators to be added. If you are not using the system for day-to-day ventilation you can drop the fans into the shaft. That can make it difficult for provision of maintenance in the future. Generally we would recommend at least an access hatch is provided, so that you have got access to the electrical connections or that provision is made for the roof ventilator to be removed and the fans pulled out if any maintenance is required. Generally, my own preference is for equipment on the roof because it is so much easier for maintenance but of course there are situations where you are either not allowed to have the equipment on the roof or you haven’t got space and in that case you just have to put the fan in the shaft and make the best provision you can.
Is there a risk that shafts open to occupiers with grills at floor level be used as storage?
Yes. Here we are talking about where we have, for instance, a door being used as the ventilator into the shaft. In principle, if the system is being used only for smoke ventilation then the only time the door is ever going to be open is either in a fire or when it is being tested. When it is being tested, someone will have to manually close it anyway so they would be able to check.
Where the system is being used for day to day ventilation as well, then yes if the door is being opened then occupiers could store something in there. Of course, they will run the risk of someone else taking it. We have come across situations where people have stored various items within shaft systems. Unfortunately that is a risk which can occur and it is best dealt with by management. However we would not generally recommend doors into shafts being used for day to day ventilation.
With regards to corridor temperatures, which regulations do you need to meet?
In terms of corridor temperature, there aren’t really any regulations. There are work place regulations which say that temperatures should not be excessive, for example not above 28degrees for a limited number of hours per year. There is however, no specific regulation covering the maximum temperatures within transit spaces such as corridors so it is simply a case of wanting to keep conditions as reasonably comfortable as possible for occupants of the building.
We’ve also written a whitepaper to accompany this webinar, which can be downloaded from this link.
Paul Compton is Technical Director for Colt, experienced in smoke control, HVAC, solar shading and louvre systems.