How it works

Yes with the appropriate control strategy it can. Comfort of a space is dependent on many variables such as the temperature, the amount of fresh air, the movement of air, the humidity etc. It also changes depending on what the occupants are doing and the time of year; what may be a comfortable environment in the summer may not be acceptable in winter. So comfort is not just about keeping the temperature of a space constant all year round and just giving the occupants the minimum amount of fresh air. By using a good control strategy and designing the system to suit each area, naturally ventilated spaces can be adapted to the needs of the occupants as the environment changes, and be comfortable all year round.

No, the e-stack system can work in a broad variety of building designs and uses. There are two design solutions for the e-stack system our roof mounted units and an atrium based system.

The roof-mounted solution is suitable whenever a room has direct access to the roof. In this case the ceiling needs to be capable of housing the e-stack unit, which is at least 1600 mm long and 950 mm wide. This is linked to the roof by a shaft and capped with a weather-proof terminal. You can choose between our R-Series and S-Series units in this situation, depending on the room design and occupancy.

Many buildings however are multi-storey and sinking a shaft to the lower floors can use valuable floor space on the higher floors. In this situation we often find that the building incorporates a central space, a perfect natural mixing chamber. In this situation our atrium system is perfect.

We use the central space as a mixing chamber, controlling the temperature in the central space and exchanging air with the individual rooms. In this case the units are installed at the top of the wall of the room. Noise attenuators are provided to preserve the acoustic integrity of the rooms and grills can be installed at the inflow/outflow of the unit. This is a wonderfully flexible system and can be adapted to different building layouts.

The Passivhaus building principles such as high levels of insulation and air tightness are properties a building should have. However, the ventilation system used on many Passivhaus schemes is mechanical ventilation with heat recovery, which is specific to German requirements where Passivhaus originated.

In Germany long periods of time there are spent in sub-zero temperatures and buildings are a net heat sink, with no net heat gains. This means dedicated space heating is often required to maintain the desired temperature and it is economical to expend electrical energy to recover as much heat as possible from the outgoing air stream.

In the UK, most buildings are actually a net heat source with net heat gains meaning dedicated heaters are not required to maintain the space at the desired temperature. It is not economically beneficial to extract as much heat as possible from the outgoing air stream, which uses relatively large amounts of electrical energy to drive the air over a heat exchanger.

No, natural ventilation can be used on multi storey buildings. You can either use our roof mounted solutions and provide shafts to the lower floors or use our atrium system. The atrium system is more popular as it requires less floor area associated with the shafts for a roof solution. Using the buoyancy head and the effective area of openings is possible to design a building to be naturally ventilated almost at every floor.

The difference in pressure between the interior and the exterior of the building varies with the floor levels; the internal pressure variation with the height of the buildings depends on the size of the openings at the high and low level of the buildings and on the heat gain within the space.

Yes the system works in buildings which are not air tight. Of course, the e-stack works more efficiently in a tight building with controlled openings.

Yes, we have helped several clients with strict noise requirements using acoustic attenuation. The attenuation can be provided at low level, by putting acoustic baffles into louvres, form part of the roof terminal, or sit within the shaft between the roof terminal and the room. Often, acoustic attenuation may only be required at high level (i.e. in the roof terminal or shaft) as this is the primary path for ventilation air.

If a room is open plan, then noise will be easily transmitted between zones, whatever the natural ventilation strategy. However if multiple rooms are present with dividing walls, yet share a common space (such as perimeter rooms around an atrium), then it is possible to link them and limit the amount of noise transmission from one space to another to comply with regulations or client requirements. This can be done by incorporating acoustic attenuation into the ventilation units that provide the air pathway between the spaces.

The purge requirement of BB101 requires that science rooms can have a ventilation rate of 10 air changes per hour.

The purging strategy depends on the type of ventilation system in place and is perfectly achievable with a natural ventilation system. When e-stack units are used in the science room, there are two simple methods of purging. If there is direct access to the roof, then the purge will involve extracting air from the room to the exterior; opening low level windows will increase the purge rate further but is not critical if an e-stack R or S-Series unit is being used.

During summer the e-stack usually acts as a high level outflow, with inflow provided by lower level openings such as windows. Using a stack increases ventilation rates above those for just opening windows.

In winter the e-stack works as a two-way duct in which cold exterior fresh air and warm interior air are mixed together at the ceiling level of the room. The fans in the units provide an effective mixing process and the mixed air enters the room at ceiling level avoiding unwanted cold draughts. This system provides fresh air to the space, maintaining the desired level of CO2 and avoids pre-heating of fresh air at low level. This natural mixing strategy results in a considerable amount of energy saving.

The system is electronically controlled measuring internal and external temperatures and CO2 levels; a panel is also provided to indicate to the occupiers whenever windows should be opened or closed to reach the designed internal comfort.

The system provides fresh air to the space by monitoring the CO2 level and avoids pre-heating of cold outside air. The natural mixing allows a considerable amount of energy saving.

The system is electronically controlled measuring internal and external temperatures and CO2 levels; a panel is also provided to indicate when windows should be opened or closed to reach the designed internal comfort.

Typical energy consumption of one unit is around 100W. CIBSE good practice energy consumption for classrooms is around 135 kWh/m2/year whereas with the e-stack system the typical energy consumption for the same space is around 65 kWh/m2/year reducing the energy consumption by 50%.

Yes it is true.

In winter cool, fresh, external air and warm, internal air are mixed within the unit at ceiling level avoiding cold draughts. The mixed air that reaches occupants is well mixed avoiding cold draughts.

In conventional building design, fresh air is provided through opening windows and needs to be heated as it enters the space to avoid cold draughts for people close to the windows. This doesnt make sense to us when in most spaces we have more than enough heat being generated to provide the pre-heating naturally.

Sometimes cooling is necessary if there are exceptionally high external temperatures or stringent requirements. A strategy should be followed that maximises the use of natural forces and night cooling, and minimises the number of hours and amount of cooling which must be used.

Yes with the e-stack system it is.

Natural ventilation can be driven in two ways; one is by wind, the second is through buoyancy (the stack effect). As air heats up it becomes less dense so will rise in a space - this is the main principle behind the stack effect.

If you have a room with openings both at high and low level, fresh air will typically enter the space through the low level openings. As it heats up due to the internal heat gains it rises and exits through the high level openings. This strategy is not reliant on wind pressures so will be effective even on days with no wind.

Opening windows can provide occupants with ventilation. However, ventilation is not just about giving people fresh air - it is also about providing comfort for occupants. Comfort for occupants cannot be achieved from opening windows alone. One example of this is opening windows for ventilation in winter; the occupants in the space will soon experience uncomfortable cold draughts. Good design adapted to each individual building, combined with a good control strategy, can help give the occupants a more comfortable environment.

The e-stack ventilation units contain relatively simple components, which also makes them robust. But there are more components than just the ones you can see, each unit incorporates temperature sensor, a room CO2 sensor as well as the controller to operate the units. The cost of the units also covers the costs of designing and programming the control strategy which is unique to the capability of the e-stack range.

The unit is a lot more than a fan in a box though it is a natural ventilation unit sized to ensure sufficient airflow through the space so that the building does not overheat in summer the natural ventilation unit is therefore rather larger than a simple fan

Underfloor heating systems normally consume less energy overall than radiators, and the relatively low temperatures required makes them ideal for utilising ground source heat pumps, which are very efficient. The downsides with underfloor systems are that there is high thermal inertia, and underfloor heating is not good at tempering incoming air.

With an e-stack system, the most efficient way of heating a space would be using a skinny radiator with low thermal inertia. This could be switched on immediately prior to occupancy to warm the space, and then switched off, to allow the heat gains from people and lighting to maintain room temperature.

With an underfloor heating system, care must be taken not to overheat the room, which could result in energy being wasted once the heat gains due to occupancy and lighting take effect. The underfloor heating system should only be used to keep the room to the minimum acceptable temperature, and switched off in advance of occupants arriving because the large thermal mass inertia will maintain temperature for some time after the system has been switched off.

Natural ventilation is a low energy way to provide a flow of fresh air through a building using the natural forces of wind and/or buoyancy.

Modern buildings tend to be well insulated to retain heat in the winter, so to prevent rising CO2 levels you need to provide fresh air. Natural ventilation is a low energy way to provide this fresh air using the natural tendency of hot air to rise and cold air to sink. By understanding how air will move naturally in a space you can provide openings that allow you to control the ventilation without the need to force this using energy intensive mechanical systems.

A heat recovery system forces incoming fresh air and outflowing stale air to be passed through a heat exchanger. The fan power used in driving the air through these devices is higher than in an e-stack unit. In very cold climates, or where there are insignificant heat gains within an occupied space, the heat recovered in mechanical ventilation heat recovery systems more than outweighs the fan power used and is a sensible solution for winter.

However, in more temperate climates and in cases where there are reasonably high internal gains, the challenge is to simply use the heat rather than recover it. A mechanical ventilation system with heat recovery is not necessary, and is in fact a higher energy option than the e-stack because the fan power used in the mechanical system is much higher.

The annulus is a circular divider to separate the inflow and outflow air paths from the e-stack to the mid-height horizontal plate located within the penthouse louvre. These are only found in our S-Series products.

Natural ventilation can work in any building. However we are pragmatists and in some building types it is not the most efficient form of ventilation.

Natural ventilation can work in any building provided that an appropriate air pathway can be provided from inside the building to outside and that the external air is of suitable quality and temperature. In practice, natural ventilation is most effective in buildings that are shallow plan, so the air does not have to flow too far laterally within the building (or through / around restrictions) before or after reaching occupants.

Manually opening windows is certainly cheaper than any form of controlled ventilation. We believe however that it is not effective at ventilating a space throughout the year.

Manually opening windows may be sufficient in the summer in some spaces. However, in winter rooms still have to be ventilated and opening windows can create cold draughts in the space requiring wasteful preheating of the incoming cold air.

With the e-stack system cold draughts in winter are avoided because the incoming air is brought in at high level and mixed with the warm air in the room. This reduces the heating requirement because the fresh air is tempered by room air which is heated by internal gains rather than from pre-heating. In the summer, the e-stack provides higher ventilation rates than simple opening windows and thereby provides cooler conditions. The natural ventilation rate can further be increased through use of one of the low energy fans in the e-stack so that a space can still be ventilated on hot and still days.

In many non-residential multi storey buildings a central atrium is often available between the floor levels. This means that is possible to use e-stack natural ventilation systems without losing any floor area. When the building has no atrium, part of the floor area will be lost for the shaft to exhaust the warm air for the lower levels of the buildings, which have no direct communication with the roof.