Friday, August 06, 2010

Carbon dioxide ventilation control in populated buildings

pd_distributionchannelsThe other day,  I’d a  talk with the Managing Director of Produal Oy, Ari Mårtensson, how Carbon dioxide (CO2) ventilation control can reduce HVAC cost in most buildings by up to 20%.

Online measurement and control leads to both energy and money savings in big buildings frequented by a lot of people.

Let’s have a look at some examples. Airports, shopping centers, office buildings, administrative buildings, hospitals, etc.


Do we understand the benefits?

But do people understand the benefits of CO2 control? I can assure you, CO2 measurement and control is a neat idea but still not so well adopted by building automation engineers around the globe.

Scandinavian systems engineers are doing a pretty good job, but the more south we go, more conservative are the control strategies of systems integrators.

Really, are they still building control strategies by the book? Is control applied without CO2 measurements, based on assumptions and / or mathematical models?


CO2 measurement and control

How can we get decision makers to change their opinions?  Money talks, how about money as a consultant in this case?

A building automation control strategy with the CO2 control, combined heating and cooling potential energy savings is estimated from 30% to more than 80% percent, depending on climate and building type.


Wow, that sounds like even more money

Most buildings’ air handling systems deliver a fixed amount of outside air ventilation, based on the  building design occupancy, which is needlessly expensive and the costliest of any air ventilation strategy.

Measurement, measurement, and measurement can save money to the owner of the building but it also leads to a much pleasurable user experience.

Average occupancy in most buildings never approaches design occupancy. Let’s take a shopping centers or airports as practical examples.

There are peak hours and low occupancies. To the degree the building’s actual occupancy is less than the design maximum, heating or cooling that extra air will directly increase energy costs.

Further, most buildings actual level of outside air ventilation is in excess of the design level, resulting in even greater over-ventilation and additional energy expense.


Viable technology

CO2 control is a viable technology to actually measure and control outside air delivered to a space inside a building, based on actual required ventilation.

It is increasingly being used to measure and control fresh air delivery to all space based on their real time occupancy to ensure code required levels of ventilation are maintained at all times.


How CO2 measurement and control works

Indoor CO2 levels indicate the amount of outside air being introduced to the space to dilute CO2 exhaled by people in a space.

  • The relationship between CO2 levels and ventilation rates is recognized 
  • Let’s measure CO2 levels on a real time basis, and adjusts air delivery to
    ensure ventilation meets actual occupancy needs to reduce over-ventilation
  • In humid climates, this can also mean better humidity control in spaces
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