Energetically efficient ventilation ducts

On occasion we talked type vents attending to degree of watertightness thereof. The standard defines four levels A,B,C y D. But, What is the importance of a ventilation system has one kind or another sealing?
In recent years there has been a steady increase in energy demands, both residential and industrial. And an important part of the energy consumption is produced by buildings.


Distribution of energy consumption in homes

The percentage of air conditioning energy consumption of a residential building is around 48%, representing increased energy expenditure and control of strategic importance.

Increased energy consumption represents a major operating cost and a higher level of CO2 emissions.

Last Kyoto Agreement, and requires all countries adhering to rationalize energy consumption in order to achieve lower emissions of carbon dioxide and improve environmental sustainability. For this purpose, the European Union issued a directive requiring member countries to work forcefully to promote buildings with more energy efficient systems.
Regarding ventilation and air conditioning ducts There are two ways to improve the energy performance of the same. Better insulation can be up to 75% energy costs and 25% for improving the sealing of the ducts.

The article in your IT RITE of 29/8/2007 determines ductwork must have a corresponding sealing to class B or higher, depending on application.
Generally, ventilation systems consist of a Ductwork of different types (rectangular, circular, Flexible etc ...) that give the system an average level of tightness of type B.
The effort would represent conduits adapted to a higher standard sealing, for example of type C or D, could represent an energy savings of up to 67 and 95% respectively according to the circumstances of each installation.
Improving ducts allow a sensible energy saving, lowering the operating costs of the facilities. But also, moving equipment would be smaller air, lower air treatment and even the dimension of the ducts themselves.
A change of this nature, move from B to C sealing would save at European level the order of 10TW h, or what is the same, could be close 3 NPPs midlevel.

Classification sealing ventilation ducts

Vent Circular versus rectangular

A duct system is never completely watertight. Usually leaks by the transverse and longitudinal joints. Air leakage increases with the pressure difference between the inside and outside of the duct.

Normally, a network of ventilation ducts is formed by elements of different typology: ducts circular, rectangular ducts, hoses, the Fibra etc..

The critical points rectangular ducts are both the metal Cross connector and as the logitudinal.

In the cross connection occurs in:

  • fixing the frame to the duct
  • the four corners
  • the contact surface of the faces of the frame when the pipes are joined together

In the longitudinal joint, air can escape to a greater or lesser amount by the fold assembly used in the plate surfaces to form the piece with the precise geometry. And this depends on the system engrafado, and the heat used in the closure of same.

In the circular duct the main points of leakage are those occurring at joints due to the clearance between the straight line section and the workpiece when plugged, areas where abuses the welding for making the longitudinal union of accessories and standard folding propeller on the conduit itself is constructed.

Classes estanqueuidad A,B,C,and D

The current Spanish rule UNE-EN 12237 sorts the channels in 4 sealing levels, At the level of D ( low to high).

The graph shows air leaks in a system l / s per m2 depending on the static pressure in the installation. Ultimately, is expressed as the sealing classification ventilation ducts.


The graph shows that a vent of the clase D this is 3 times that of the sealed clase C, which in turn is 3 times that of the clase B and himself on.

The tightness of the duct is defined by the following equation:

f= c×p0,65


Clases A,B,C y D

Clases A,B,C y D

f represents air leakage in dm³ / s · m²

p is the static pressure in Pa

c coficiente is the class that defines the sealing

Class c = 0,027

Class B c = 0.009

C Class c = 0.003

Class D c = 0.001

What kind of canal is tight? Consider the degree of tightness that offer regular vents. We considered that are well built and assembled workshop ducts properly with sealants and mastics manufacturers recommended.

  1. Circular conduit for union with plug sealed with putty on tape : Classification B
  2. I circular pipe plug connection with O-ring: Classification C
  3. Duct with rectangular frame preformed: Classification B-C

With very careful and elaborate constructions can achieve degrees of tightness circular duct type D and type C in rectangular duct.

Importantly as well built in a duct where attention to the smallest detail, with high expectations sealing, fustradas these can become careless and wrong with mounting. Thus, the manufacturer must inform and prepare the installer on knowledge of the characteristics and virtues of each duct system to conserve and enhance the properties thereof. Good conduct is the basis for running a good ventilation network. A precarious passage can not possibly provide a good seal to the system even with the good work of the editor.

How do we know that class watertightness have a facility? Measuring the level of sealing is effected by a facility specific field analyzers, on several representative samples of the entire network installed duct. Each sample will consist of straight and accessory parts with a minimum length of 2,5 m and an upper surface to 10m2. Furthermore the relationship between the total length of joints and pipe surface is greater than unity. The assay is carried out both positive and negative pressures , at least 5 measures each, within a pressure range up to the maximum static pressure. The duration of each step is at least 5 minutes.