Image Image Image Image Image Image Image Image Image Image
Scroll to top


Contradiction Matrix for Airflow

Using the Contradiction Matrix to Improve Airflow

| On 05, Nov 2007

By Prashant Y. Joglekar

On a hot Sunday afternoon, I was cooling myself under a fully blasting air conditioning unit while watching a TV show. During a commercial break, there was an advertisement for a leading shoe brand, claiming that its shoes breathe. Suddenly the power went off and I started sweating. There was a strange feeling as if I was traveling from the North Pole to the equator. “If shoes can breathe, what about our homes,” I thought to myself. I was so happy that we have windows (our home’s nostrils), our natural ventilation resource. With trees surrounding my building, my pain subsided to a reasonable extent with shade and a breeze.

Windows are an integral part of our “home sweet home,” workplace and any number of establishments that want to be open to keep an eye on the world. From a TRIZ perspective, windows are one of the greatest innovations solving a major physical contradiction: “I want to be in and want to be out.”

The window is also the subject of poetic work; there are many literary masterpieces written on the subject. The word window seems to have brought lot of luck to the technically-minded – Microsoft’s products are prefixed with “Windows.” Windows has thus bestowed fame and wealth upon Microsoft’s founder, Bill Gates. His generosity is also helping an opportunity-starved world with a ray of hope, with can be thought of as breathing freely, through his foundation. All of this is because of windows. As these thoughts came to mind, a few contradictions also dawned.


Using TRIZ to analyze the wonder of windows, the first thing we do is start looking at the functions of the window. (We need to do this for any system in order to innovate – this is an essential step, functional and attribute analysis.) Let us look at some of the main and auxiliary functions of windows:

  • To receive sunlight
  • To receive fresh air
  • Facilitate movement of air from outside as well as from inside
  • To communicate with a person who is outside or inside
  • To see a person and communicate
  • To pass something between outer house walls
  • Refresh a depressed mind by looking at nature or street happenings
  • To enjoy the rain while dry inside
  • Symbolically represents our willingness to be open to the world
  • Opens and closes our interface with the outside world


For this discussion let us look at only one key function to identify the contradiction(s) associated with it: we have windows because we want to have better ventilation, which also helps to keep the air quality/ temperature inside the room at a comfortable level. During the day we want the windows to be open, but during the night we want them to be half- or completely closed. In summer, we want air circulating so we keep the windows open or completely closed (if we use an air conditioner). During a monsoon, we close the windows to prevent rain water from coming inside.

The system needs to cater to all of those specified requirements. Consider this – I want the window to be as open or closed as I want, at infinitely variable levels at different times. From a TRIZ perspective, this is a physical contradiction in time and needs to be solved by looking at the relevant inventive principles.

The system needs to cater to all of those specified requirements. Consider this – I want the window to be as open or closed as I want, at infinitely variable levels at different times. From a TRIZ perspective, this is a physical contradiction in time and needs to be solved by looking at the relevant inventive principles. The inventive principles that can be used are: dynamics, preliminary action, periodic action, beforehand cushioning, partial or excessive action, skipping, copying, mechanical vibration, thermal expansion, discarding and recovering, preliminary anti-action and continuity of useful action.1

The first principle in that list, dynamism, says to split an object or system into parts capable of moving relative to each other; if an object or system is rigid or inflexible, make it movable or adaptable.

The answer is sliding widows as shown in Figure 1. Sometimes we wish that we could have all sliding windows. There is one problem with them, however – they can never be fully opened as the window frame limits their range of motion. As Figure 1 shows, with four sliding windows, the total open area at any given time is only 75 percent. If you have two sliding windows, then they are half open.

Figure 1: Sliding Windows

With this new contradiction of an only partially open window, can we generate other ideas to satisfy our basic function – having an opportunity for ventilation? For better ventilation, we want more air to come in and more to go out, so more can come in, etc. This will be possible only if the air inside moves faster and without any obstruction. The contradiction matrix suggests the parameters that best fit this situation (see Table 1) – we are trying to maximize the amount of substance (air) and its speed (the received air needs to be moved at a higher speed for better ventilation) while the parameter that worsens is the frame area, the matrix parameter, the area of the stationary object.

Table 1: Selection of Inventive Principles
Parameters To ImproveParameter That WorsensSuggested Inventive Principles
1. Amount of substance
2. Speed
Area of the stationary object

Parameter changes, 35
Porous materials, 31
Asymmetry, 4
Merging, 5
Local quality, 3
Another dimension, 17
Curvature, 14
The other way round, 13
Taking out, 2
Composite materials, 40

Let us list the system’s elements/resources and try to apply each of these inventive principles see whether we can generate some useful solutions. (See Table 2.)

Table 2: Analysis of System Elements
Elements/Resources of Living SpacesUseful Attributes of Elements
Living roomLength, height, width
FloorTemperature gradient
Window frameLength, height, width
CurtainFlexibility, porosity, material properties
Window glassHardness, transparency
Building materialPorosity, temperature gradient
Free space around windowAll dimensions of space
Atmosphere around buildingWind speed, direction

Idea Generation with Inventive Principles

Another Dimension, 17

» If an object contains or moves in a straight line , consider use of dimensions or movement outside the line; if an object contains or moves in a plane, consider use of dimensions or movement outside the plane

The window shown in Figure 2 demonstrates this principle; the window has marble/granite flat tile running parallel to the parapet’s length and going outside the boundary. The sliding window goes out and, thus, you get a completely opened window.

Figure 2: Window Using Another

What about using the balcony? Many buildings provide balconies, outside and hanging in free spaces. These balconies can be used by the occupants for breathing fresh air (we are in, we are out). These balconies bear some similarity to a nose – they are external, but help all our internal systems by taking in fresh air. Figure 3 shows some such balconies.

Figure 3: Curved and Protruding Balconies

Porous Material, 31

» Make an object porous or add porous elements; if an object is already porous, add something useful into the porous

Can we make the window glass porous? Or can we replace glass with some porous object? The fine nets that are fixed in the window frame allow fresh air to enter while offering protection from mosquitoes. (See Figure 4.)

Figure 4: Windows– Glass in
Two Frames and Nets in
Other Two

Taking Out, 2

» Extraction of unnecessary part

Can we take out something from the balcony wall? French windows are the best to maximize the air flow; they are big and allow a lot of air to enter a room.

Local Quality, 3

» When an object or system is uniform, make it not uniform

Two windows can have nets and two can be glass. If you have a need for privacy, use curtains. (This presents another contradiction that will need another solution.)Or the balcony wall may have some openings running parallel to its length, taking it from a single solid structure to a structure with cavities.

» Change the things around the system from uniform to non-uniform

What is around the system? Air. We can use a fan to suck the air in and have it backed up by a generator. Air conditioning/exhaust fans are some of the artificial means to move the air and keep your house breathing.

If you live by water, wind will solve your ventilation problems as the wind pressure (external environment) will drive out the air inside your house, providing a continuous flow of air. Your home can breathe naturally, just as we do when we visit the seashore. Buying a house near the sea may be the least expensive ventilation option.

» Enable each part of a system to function in locally optimized conditions

In case there is no power, we can use hand fans to move the polluted/stagnant air away from us, so that more fresh air can come in.

Asymmetry, 4

» Where an object or system is symmetrical or contains lines of symmetry, introduce asymmetries

If most of the free air outside your window is blocked by other buildings, then better town planning may be the answer. Or try asymmetrical building layouts, such as having a garden in front of your building to allow for greater open space.

Curvature, 14

» Turn straight edges, or flat surfaces, into curves

Some building side walls are curved; this allows an unrestricted flow without a loss of wind pressure. Protruding, curved balconies can also guide airflow in your house.


I do not claim that the ideas generated here are the only ventilation solutions – one can further generate more ideas. This is an attempt to demystify and demonstrate the use of the contradiction matrix to generate ideas for our day-to-day concerns. In solving any problem or finding any opportunity, we come across several contradiction chains. Each of these chains can be solved only by defining the root contradictions correctly. Talking clearly and using simple words, correct contradictions can be formulated. One way of improving the power of observation is to think about contradictions; if all cannot be solved, it is still smart to try to stay ahead of some.


  1. Mann, Darrell, Hands-On Systematic Innovation (Technical Version), CREAX Press, 2002.
  2. Mann, Darrell, DeWolf, Simon, et. al., Matrix2003:Updating the TRIZ Contradiction Matrix,CREAX Press, 2003.