The Benefits of Natural Ventilation over Air Conditioning »

The challenge of rising energy costs, increasing environmental concerns and subsequent legislation has led to increased awareness of buildings energy consumption and carbon emissions. The main result of which, in terms of building activity, has been to find new ways of significantly reducing energy consumption particularly where associated with heating and air conditioning.

Natural ventilation is very attractive solution to this problem for designers and architects because of it's capability of providing an acceptable indoor air quality and meeting comfort needs throughout the full range of climate conditions. In most cases, the minimum ventilation rates needed for indoor air quality are easily reached and the maximum ventilation rates needed for summer thermal control of the building are well identified.

Natural ventilation is a logical and suitable strategy for many types of buildings, such as low rise dwellings, schools, small or medium sized offices, recreation buildings and public buildings in moderate or mild climates. Natural ventilation is also very cost effective compared with the capital, maintenance and operational costs of mechanical systems and does not require any plant room space.

Recommended ventilation rates according to British standards BS5952:1991:-

8 L/s Per occupant
3 L/s per m2

Ventilation rate per occupant »

Ventilation rate per m2 »

As can be seen the windows do not supply the required ventilation rates at low and even moderate external wind velocities, however the Windvent achieves the rates at low external wind velocities.

Air Conditioning vs. Windvent »

The above table of running costs is based upon the following information:-

• A/C average yearly running time of 500 hours
• Electricity charge of 6.4p per Kw/h
• 7Kw inverter cassette - 24 m/2 office with 12 persons

The average install cost of an A/C system inclusive of electrical connections, controls, condensate pumps, ductwork connections, labour, access & builders works is £15,000 for an office of 24 m/2 coupled with the cost of running for a national average of 500 hours per year, coupled with maintenance and parts contract implications. The average yearly running cost over a 5 year payback period would be £6650 net. However after the 5 year period has elapsed the continuation of electrical supply costs and parts and maintenance charges would still apply based upon an average of £3650 per year.

The average install cost of a Windvent system using manual controls inclusive of terminals, dampers, ductwork connections of 1.5m, labour, access & builders works is £24,850,000 for an office of 24 m/2. There are no maintenance costs and a natural air supply is available all year round with no electricity costs. The average yearly running cost over a 5 year payback period would be £4970 net. And nothing after the 5 year period has elapsed.

Conclusion »

The results speak for themselves, the Windvent system offers a ‘fresh’ cool air supply all year around and is dependant on the individual occupant requirements.

Environmentally it is far more efficient and carbon neutral (ie. leaves NO CARBON FOOTPRINT on the environment).

Having a fresh air supply to an office environment has been proven to reduce staff sickness and improve productivity over offices that have air conditioning or mechanically cooled ventilation.

The cost saving in monetary terms over a five year payback period would be on average £1680 per year, and after the payback period an average of £3650 based upon annual running and maintenance costs of an air conditioning system within a medium to large office installation.