Right welcome to another video in our series of videos for ventilation from EnviroVent
we're just going to talk about systems, what we mean by that within approved document f,
technical handbook and technical guidance for Scotland and Wales they have what we call
systems for ventilation, now these systems differ. We've got one, system one, system
two, system three and system four at the moment we're going to talk about system one, system
one is known as intermittent extracts fans and background ventilators, now the reason
I mention the word background ventilators what we mean by that is a trickle vent, now
these maybe in the form of one that would be fitted around the window frame, in the
window they can go through the wall, various sizes and various lengths this is a standard
size what's known as two thousand five hundred millimetres squared of the equivalent area,
so that's the amount of air it can let in and out now these are generally fitted in
the windows in the habitable rooms you'd also have one in each wet room a lot of it depends
upon the size of the property and the occupancy level as well what we'd have here we'd have
a series of what we call localised fans, so you'd have a fan in the kitchen, one in the
bathroom, then you'd also have one in the utility, an ensuite or a WC and even what
we call a wet room, so you need to extract the moist air from the bathroom to outside,
also within a kitchen if you've got any moisture from cooking also any contaminants or any
odours, so we've got to make sure that we extract to atmosphere so these are what is
known as intermittent fans, so they are off most of the time and they come on as and when
required or you have a manual override or maybe in a bathroom it might be wired to the
light switch so somebody will turn the light on, the fan comes on, turn it off it should
then run on for a period of time generally a minimum of fifteen minutes to ensure it
can get rid of any moisture or odours or anything like that. These fans come in various formats,
i'll get my esteemed colleague just to pass me on here, so this is what is known as an
axial fan, these are sort of a low powered one, low energy they don't move large amounts
of air, if you want to move a large amount of air you've got to have a bigger fan, this
one has a four inch duct if we wanted to move more air we've got to use a bigger ducting,
we may go up to six inch especially for a kitchen and designed really to go straight
through a wall, some of them can be ceiling mounted, you've just got to be aware of the
some of the installation issues, make sure you follow. Ideally say if you were installing
it in a loft space, going out to atmosphere maybe a roof tile vent or it could be through
the soffit or a gable end wall we need to make sure the ducting may need to be insulated,
you might need a condensate trap on the back also the lengths need to be kept to a minimum
again there is guidance, with a fan like this if you're using flexible ducting it should
be kept to a minumum of one point five metres, which isn't a long sort of length. So ideally
straight through the wall and out to atmosphere, we do also have what we call if you've got
longer lengths of ducting limited to them (again I'll just get my esteemed colleague
to pass me that one) So we've got longer lengths of ducting you might use a high powered fan,
like this one this is a centrifugal fan so these can cope with longer lengths of ducting
higher air flows but still utilising a four inch duct, so you know the only thing is they
are a little bit noisier because you're moving more air and you're coping with more resistance,
so they are going to be nosier than your standard axial fan. Normally you'd use a centrifugal
fan one the kitchen going off to atmosphere, that's it really for intermittent fans you'll
find because of the fact you've got the intermittent fans there is a requirement for a lot of background
ventilation, some properties you might require a sort of twenty four trickle vents and you've
got to have one in each window, one in the wet rooms so it's quite a lot of background
ventilation you require, the idea of that is when the fans are on you've got to replace
the air you're taken out so that is then drawn in through the trickle vent, also because
the fans are off most of the time they might be off for twenty to twenty two hours a day
you still need to ventilate that property with what we call a background ventilation
rate, that's what the trickle vents are going to do, depending on the wind direction you're
still going to get some ventilation in there. There are requirement within the approved
documents showing you how many background ventilator you need depending again as I say
on the size of the property, it will also depend on how new and how air-tight the property
is, so if we start using double glazing, cavity wall insulation like we do with new builds
then you know you're going to require more background ventilation hence one of the reasons
why if you look at this we can see a new-build it's good practice but not best practice,
the only reason being is because with new builds, now we're making them quite an air-tight
property to keep all the heat in and then we're going to put a lot of holes in the building
with the background ventilators, if we're using these fans so you know we've got a compromise
there we're trying to make it air tight to keep the heat in and then we're penetrating
the building with a lot of holes, not ideal but it's still good, still a traditional way
good fro refurbishment, major or minor but gain it's just being aware of this requirement
for the background ventilation what you may get is people replacing windows with double
glazing, don't replace the trickle vents suddenly these fans aren't going to be as effective
as they used to be. That's it for system one really, we'll move onto the next system, we're
actually going to skip one of the systems which is known as system two because at EnviroVent
we don't deal with that system it's known as passive stack ventilation and there are
various reasons why we don't deal with that but we're going to move straight onto system
three and I'll see you in a second.