Why would you want to install passive stack ventilation within your home? Well, there are lots of different types of people out there and we all have our own unique views on what makes an eco-home and what we demand from materials and products we place in our homes. Some of you will want to create a home that has as low a carbon footprint as possible while some of you will just want to reduce your bills and make your home a little greener.
For that reason there are also different types of ventilation that will suit your specific requirements. If you're after a system that will be as efficient as possible at recovering heat from expelled air and you don’t mind using electricity to achieve that, then you might want to look at MVHR (mechanical ventilation with heat recovery). But if you want to produce a home that uses the minimum amount of electricity, then you’ll probably want to install some form of passive stack ventilation as it uses no electricity at all, and it has other advantages as well...
Passive stack ventilation (PSV) is a natural and low cost method of ventilating your home. It doesn’t use electricity so you can reduce your electrical load requirements and it should be maintenance free.
I should start by explaining the concept of passive ventilation, which works on the principle that warm air rises and wind blowing across the face of your roof or walls causes negative pressure which sucks out the warm air. So in its simplest form you could open a skylight window or a window at the top of your house (because as we’ve established warm air rises). As this warm air gets sucked out at the top floor, cool air is sucked in through trickle vents in your windows and gaps around services etc to replace it.
Passive stack ventilation expands on these same natural principles in order to provide ventilation by way of extract vents within the wet rooms of your property such as en-suites, bathrooms and kitchens which are routed vertically to the outlet vents at the ridge of your roof. Replacement air is then supplied by trickle vents in your windows or wall vents.
The intelligent PSV system works on the same principle as above but includes the addition of humidity sensing vents in the inlets and extracts. These detect humidity in the air and react by expanding or contracting which opens (increasing ventilation) and closes the vents (decreasing ventilation) depending on the humidity levels within the property.
These intelligent vents and trickle vents don’t require any electricity to operate as they tend to use nylon filaments within the vents that expand and contract relative to the humidity levels in the individual rooms within the property and should therefore be maintenance free. The main advantage of this system is that it will self regulate the ventilation.
A standard (non-intelligent) PSV system is open all the time meaning your ventilation is dependant on the wind speed externally and the heat of the internal air which causes unnecessary heat loss and you’ll likely have to run your heating boiler more in order to heat the cooler air coming in through the inlet vents.
There are companies who offer an element of heat recovery to passive stack ventilation. However this does involve adding a heat pump to the system which will mean you’re using electricity to run the heat pump.
If you’re after a zero energy system this isn’t likely to work for you. But if you’re prepared to accept some electrical input then you will be able to cool the incoming air in the summer months and capture and recirculate the heat from outgoing air in the winter months.