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Natural Ventilation Solutions

Natural ventilation, unlike mechanical fan forced ventilation, simply uses the naturally occurring pressure differential forces of air movement, wind and buoyancy to deliver a steady supply of fresh air for building ventilation and space cooling.  In an environment where energy conservation is at a premium this sounds ideal…and it is! Naturally ventilating a building actually offers the best of both worlds combining little or no energy consumption with low capital costs whilst still providing adequate fresh air and comfort temperature conditions throughout the year.  With plant room also eliminated, services space minimised and lower service/maintenance costs Natural Ventilation now makes for one the most practical choices of the day.

The Gilberts Mistrale Natural Ventilation Solution
Natural ventilation systems comprise a number of constituent component parts. Although windows can sometimes be employed the Gilberts system does not embrace this. Window based systems can be simple but are also inherently disadvantaged. With natural ventilation systems often using low overnight temperatures for cooling, opening windows are particularly undesirable from a security aspect. Other issues such as noise penetration and water ingress are also difficult to avoid and window motorisation can also compromise aesthetics. They also may not offer the fine levels of control and balance required for a modern operational system. For this reason the Gilberts system focuses on using optimum performance components that include a secure intake louvre, a fully controllable insulated volume control damper, a heating or cooling coil, a fascia grille and intake/exhaust penthouse roof turrets.

A typical natural ventilation assembly comprises of an intake louvre, regulating damper and fascia grilles. Installation options are varied with the opportunity for window installation, low level floor, under floor or over ceiling.  This installation strategy will affect your choice of louvre, damper and fascia components.

Under Floor Natural Ventilation Systems
An under floor ventilation arrangement gives the opportunity to keep walls and window areas free or be used for areas where external wall areas may not be available. A louvre intake and damper arrangement draws air into the floor  void and distributes this into the room at floor level through standard design floor grilles. The cool fresh denser air displaces the lighter warm air upwards where it is extracted through high level wall grille and damper assemblies into the stack. Under floor systems which have fewer depth/thickness restrictions also give greater opportunity for acoustic insulation in areas where external noise might be a problem.

Low Level Natural Ventilation Systems
Low level installations, whether in glazing or the wall structure itself, are the most popular installation location providing for optimum air flow and comfort conditions. Cooling outside air will be drawn through the assembly at low room level ventilating through higher level wall grille and damper assemblies into the stack.  Since the airflows are usually unrestricted this typically maximises the air movement efficiency.

Ceiling Natural Ventilation Systems
Similar to an under floor installation a ceiling displacement arrangement gives the opportunity to keep walls and window areas free or be used for areas where external wall areas may not be available. Cooling air is drawn in through a louvre damper arrangement for distribution through traditional ceiling diffuser outlets.  The cooler air sinks displacing the warmer stale air which can then be drawn out into the stack through higher level wall grille and damper arrangements. Because natural ventilation relies mostly on a buoyancy effect ceiling systems are inherently less efficient unless they are also wind driven. However ceiling systems again have fewer depth/thickness restrictions and so also give greater opportunity for acoustic insulation in areas where external noise might be a problem.

Mistrale Natural Ventilation Standard Configurations
Gilbert’s Mistrale Natural Natural Ventilation system has been developed with maximum project flexibility in mind. Different buildings and structural designs combined with the building location and purpose will present a wide variety of restrictions which affect system selection. As standard there are 6 model configurations (Model A to Model F) but the ability to pick and mix the various components of Mistrale Natural Vent enable us to adapt the product for a multitude  of different installations too.

Mistrale Natural Ventilation catalogue

Natural ventilation, unlike mechanical fan forced ventilation, simply uses the naturally occurring pressure differential forces of air movement, wind and buoyancy to deliver a steady supply of fresh air for building ventilation and space cooling.


Mistrale Model A-Low Level Intake Unit with Heating or Heating/Cooling Coil

Model A is the most popular natural ventilation unit choice and is primarily intended as a supply/intake unit for floor mounting installation.


Mistrale Model B - I Intake Unit with Heating or Heating / Cooling Coil

Model B is a further variation on Model A and is primarily intended for installation above the floor level at low or middle room heights whilst still providing for optimum  air flow and comfort conditions.


Mistrale Model C - Concealed Intake Unit with Heating Coil.

Model C is an alternative to the popular Model A and is primarily intended as a supply/intake unit for installation above the ceiling or below floor level.


Mistrale Model D – Intake Unit without Heating Coil

Similar to Model C Model D is primarily intended for installation above the floor level at low or middle room height and provides for optimum air flow and comfort conditions.


Mistrale Model E – Exhaust Unit

Model E is primarily intended for installation at high wall or stack level to provide an external outlet for the warm stale exhaust air.


Mistrale Model F – High Level Transfer / Exhaust Unit

Model F is primarily intended for installation at high room level for exhaust or transfer application. Stale warmer air from the room will be drawn through the assembly into the stack.


Mistrale Natural Ventilation Components
Depending on the ventilation strategy and the preferred location the installation may require  a mix and match of various standard components

Intake Louvre

Gilberts intake louvres provide a high weather efficiency design with only a standard single louvre bank arrangement. This slender robust but weather efficient and patented design offers a much lower pressure resistance than conventional double bank weather louvre designs. This allows the use of smaller face areas for any given air requirement or provide more air volume for  a given face area. Structurally strong they can be installed in either windows or walls.


Regulating Damper

Close control is one of the key factors for an effective NV system with the ability to regulate airflows accurately to meet occupancy levels and temperature requirements vital. The patented Gilberts volume control damper is a unique design that is fully adjustable ranging from full open to full closed. When closed the damper has an extremely low leakage rate that prevents draughts and system inefficiencies.

The casing is manufactured from low conductivity material which prevents any cold bridge effect allowing total isolation from internal to external areas.  Furthermore the damper comprises a double insulated blade arrangement which means that the damper has a very low ‘U’ value (when closed) of 1.6 w/m2/C, which is as good as a sealed double glazed window unit which prevents wasteful energy losses or gains. The insulation also provides a secondary acoustic reduction.


Heating and Cooling Coils

Heating coils add a wide degree of flexibility to the system allowing heating to be employed within the design. When used for heating the system air movement is accelerated, resulting in a faster and more efficient heating process as compared to pure radiator based systems. Alternatively cooling coils or duel purpose heating/cooling coils can be fitted to reduce air intake temperatures.


Fascia Grilles

Gilberts manufacture a wide variety of fascia grilles and diffusers for floor, wall or ceiling mounting.  With a wide range of both standard and bespoke tested designs we can provide grille design solutions to meet the requirements of the most demanding projects. Decoratively designed punched panels can also be used on internal faces which can be fitted with insulation to maintain a low, burn preventive, surface temperature.


Intake/Exhaust Penthouse Louvres

The Gilberts intake/exhaust turret can be specifically manufactured in a wide variety of configurations to suit the system design parameters. The turrets can be designed to suit wind driven systems or stack effect with internal partitions and dampers providing for full and accurate air movement control. Specific designs will use a combination of some or all of these components alongside a bespoke controls strategy using room temperature and/or CO2 sensors to maintain comfort conditions.


Silencer & Acoustic Information

Extensive acoustic testing has been carried out in order to establish the noise reduction values which could be reasonably expected from each component of our Natural Ventilation assembly. 


Mistrale Natural Ventilation Control

Natural Ventilation systems require accurate control and a well thought out control philosophy to achieve the desired conditions within the space. With this in mind Gilberts can provide full control packages or can work with external control houses to intergrate free issue controls within the Mistrale system.