Energy efficient make-up air should be on everyone’s menu

An increasing number of commercial buildings require improved ventilation – often to create a cleaner atmosphere that meets health and safety and COSHH requirements, or simply to provide a more comfortable environment for employees. Danny Packham European product Manager – Warm Air and radiant for Nortek Global HVAC UK Ltd explains the developments in make-up air heating solutions to meet ventilation and air distribution requirements at a time when energy costs are escalating.

In commercial buildings, good ventilation will keep bad odours, irritating pollutants and potentially harmful gases like carbon monoxide at bay. Plus, it prevents the formation of mould and/or mildew, which is vital for employee health and building hygiene – especially important when in a kitchen or food processing environment.

When production processes get underway, air quality can quickly deteriorate. Raised levels of indoor air pollution may reduce productivity, as well as having negative effects on the comfort of the building’s occupants. Certain industries are prone to airborne particles that can make life very unpleasant. Automotive manufacturing processes, for example, produce oil haze that hangs in the air. In other industries, chemical processes may generate foul vapours.

An extract only ventilation system will create negative pressure environment, resulting in replacement air being drawn from adjacent areas via door openings and structural gaps. In winter, this will introduce cold external air into the building, creating discomfort for its occupants.

One alternative to an extract only system, is to introduce a ‘make-up air’ or supply air heating system that replaces the extracted air with conditioned fresh air. In this way, the environment within the building can be closely controlled, and never left to the mercy of external weather conditions.

Make-up air systems are doubly advantageous – they create even temperatures throughout a building and ensure that extraction systems perform efficiently. If make-up air is not provided, an extract system has to work harder and the capacity will be reduced, producing system inefficiencies. The result is negative pressure within the building as unheated air is drawn in from around the perimeter, causing uncomfortable draughts and drawing dust and dirt into the production space. Similarly, existing heating systems are unable to operate effectively.

Make-up air heating units provide a highly effective solution to the problem of maintaining both air quality and stable internal temperatures. They deliver a balanced volume of replacement air into the body of the building. This creates a slight but uniform positive pressure throughout the internal space that inhibits the infiltration of cold external air and airborne dust.

This principle not only allows the extract system to perform more effectively, but also provides cost effective heating. Without make up air comfort conditions are difficult to achieve with cold draughts at low level and heated warm air rising to high level without any benefit to building occupants working at floor level.

Reznor make-up air heating systems offer a solution in many different types of the building – both where extraction is a constant rate or varies throughout the day to match production criteria.

The Reznor packaged make up air units such as PREEVA, IDF-BDX and RTU provide replacement air tempered to a pre-determined design temperature and maintain this temperature whilst extraction in in operation, whilst 100% thermal efficiency provides reduced energy usage. Where extracts rates vary, further energy savings can be achieved by using a variable air volume make up air unit. The volume of replacement air provided automatically adjusts with the changing extract rate thereby reducing both the electrical and gas usage. In summer, the make up air units also provide ‘free fresh air cooling’.

Working together with Mitsubishi Electric, Reznor were able to develop a bespoke heating, ventilation and cooling system solution for McDonald’s Restaurants Ltd that reduced running costs, was transferable across sites and improved customer experiences with a reliable, consistent and comfortable temperature inside all restaurants.

McDonald’s Restaurant’s Ltd were looking to create a comfortable environment for customers through a more energy efficient heating, ventilation and cooling system, The new Air Handling Unit from Reznor is used for cooling, heating and ventilation and resulted in McDonalds Restaurants Ltd cutting their running costs by over £4500 for each site, whilst reducing their carbon emissions significantly. The fast food giant also saw a massive 35% reduction in energy consumption across approximately 650 UK restaurants following the installation of the Unit developed by manufacturers Reznor and Mitsubishi Electric.

Dave Holden Building Services Consultant: UK & Ireland for McDonalds said, “It is commercially critical for us to operate effectively all year round. Our customers expect McDonald’s to have a comfortable internal temperature and the ability to offer that, reliably and consistently, is part of our relationship with customers.” He added, “When we started looking at replacing our air conditioning equipment we quickly realised we needed a bespoke system. We were coming at this with very specific requirements and off-the-shelf systems didn’t satisfy the need.”

The innovative solution combined Reznor’s IDF Units with Mitsubishi Electric’s Air Source Heat Pumps, which were controlled by a building Energy Management System supplied by Powell Systems Ltd to achieve maximum operating efficiency. Following an initial trial in two restaurants, the results were impressive and saw an annual saving of £4,515 per year and on average 20 tonnes less CO2 emitted. The solution was designed to accommodate a variety of standard sized Air Handling Units previously installed so that the replacement solution could be rolled out across all 1200 restaurants.

Intelligent combined heating and ventilation units are also an ideal cost effective and fuel-efficient solution for a variety of industrial applications, warehouse and logistics, bars and restaurants.

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