Effective and economic indoor air quality

Jaga, space heating, ventilation, IAQ, CO2

While indoor air quality is important in all types of working environment, it has become a major issue in schools because of the accepted principle that poor indoor air quality adversely affects the attention of pupils in classrooms and their performance. As Paul Kingswell, commercial manager with Jaga Heating Products UK, points out, there is a lot of legislation and guidelines. They include Part F of the Building Regulations and Building Bulletin 87 relating to schools. And local authorities may have their own requirements.

Paul Kingswell asserts, ‘CO2 affects behaviour more than temperature. A good target for CO2 concentration is 1200 ppm or thereabouts. Lower is expensive in terms of energy costs, and higher is poor indoor air quality.’

It was to meet the requirements for indoor air quality in school classrooms that Jaga introduced its Oxygen combined ventilation and heating system four years ago. One of the best known installations is Haydon Wick Primary School in Swindon [you can find it on the MBS web site using the search engine]. Tests carried out with BRE demonstrated its effectiveness and how savings of 20% could be achieved compared with natural ventilation.

Now Jaga has developed a new generation of Oxygen based on the latest components such as speed-controlled EC motors. It can be used in buildings of any age and type and provides an intelligent and fully controllable heating and ventilating solution that enhances indoor air quality in an energy-efficient way.

There are two types of system — Natural and Dynamic (powered by fans).

While some specifiers might prefer the Natural system, perceiving it as ‘greener’, it has disadvantages that might more than offset its potential BREEAM points. They include limited CO2 control, being affected by wind speed and direction, less scope for night-time cooling and CO2 levels in classrooms often above 1000 ppm and frequently exceeded 2000 ppm, according to research by the Technical University of Denmark.

So let’s focus on the Dynamic system (see diagram).

Controlled and tempered fresh air can be provided by adding Oxygen Refresh units to Jaga low-water-content radiators.

It is based on a range of Jaga low-water-content radiators that have within their case ample space for Oxygen Refresh units, according to the requirements of the space. The radiators are mounted on outside walls, and the Refresh units draw air from outside through a small duct in the wall, pass it through the heat exchanger to be warmed and delivered to the room at low level — displacement style.

Room air also circulates through the radiators to be warmed. Air is removed from the room at high level, and the rate of air supply and extract are carefully balanced. During hot Summer months, Oxygen’s boost function can deliver night-time cooling.

The ventilation rate is controlled according to demand, so rooms are not ventilated unnecessarily, thereby wasting energy.

Jaga has some useful experience in the application of the Oxygen system, as Paul Kingswell explains.

Building Regulations recommend a daily average air supply of 5 l/s per person, which for a classroom with 32 people in it would require six Refresh units. However, Paul Kingswell tells us that Oxygen can maintain design CO2 levels with fresh-air rates as low as 1.9 l/s per person, which can be achieved with just three Refresh units and consequent saving in capital cost.

His advice is ‘In reality, every project should be designed on its own merits, bearing in mind that Oxygen is demand controlled.’

The system is on trial at Sudbury School in Wembley, the new headquarters of Hull Police and Chuckery School in Walsall.

For more information on this story, click here: March 2012, 70
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