Electrical & Mechanical Controls Ltd – EMC LTD 21 Years of experience counts. Phone 01603 625535

Natural Ventilation Control

New or upgraded buildings are increasingly adopting natural ventilation for an eco friendly alternative to conventional methods of forced air ventilation. Some schools are using this approach to great effect throughout the UK. EMC can provide your project with the correct control to keep your building regulated as it should be. Should you have a forthcoming project that includes this type of equipment then we would be happy to take a look and give you a quotation.

Controls

The technology revolves around using actuated openings to control airflow throughout a building. There are numerous building configurations that are used with natural ventilation. One format revolves around creating a stack effect by using high level extract louvres installed within the roof space (chimney). Low level louvres are installed within rooms to allow for air to travel up and out of the buildings high level louvres. This moving of warm air up and out creates a cooling effect within the fabric of the building (the thermal mass). The buildings fabric in most new builds is built around this principal for creating a natural cooling / heating effect. In terms of temperature control, room detectors are installed for monitoring. A client would be given a choice if they would like to individually control the environment for the room or a via a common controller / head end PC or web server. This sensor can monitor both temperature and co2 throughout the occupancy period to adjust the louvres to regulate the temperature and air quality. This is especially good within a school project as the a co2 level of 1500ppm and below must be maintained for regulations. Fresh air within a building is essential for good brain activity. Feeling lethargic within a building could well be due to co2 levels being too high or ineffective use of plant for air changes. Correcting this helps to maintain a healthy environment for your work be it in a data centre or primary school. A weather station can be used to monitor climatic conditions and via the automatic controls override  associated plant should it be necessary. The controls strategy can be tailored on a project by project basis as every building is inherently different. The one size fits all analogy does not apply when dealing with industrial controls.

Room User Interface

Combined temperature and CO2 detector

I have naturally (pun intended) over simplified the process above there are many factors to be taken into consideration with regards to initial building design and expected building usage.

The theory….

The Thermal Mass

Essentially thermal mass acts as a thermal battery. The building acting as a heating and cooling battery. Thermal mass is not a replacement for insulation. Thermal mass stores and re-radiates heat. Insulation stops heat flowing into or out of the building. A high thermal mass material is not generally a good thermal insulator.

Summer Time

In the summer the thermal mass allows cool night breezes and / or convection currents to pass over the thermal mass, drawing out stored energy. Also during the day this protects the thermal mass from excess summer sun with shading and insulation.

Winter Time

The thermal mass absorbs heat during the day from sunlight or from underfloor heating. It will then re-radiate this warmth back into the building throughout the night.

Wiki Information – An alternative explanation

Natural ventilation is the process of supplying and removing air through an indoor space without using mechanical systems. It refers to the flow of external air to an indoor space as a result of pressure or temperatures differences. There are two types of natural ventilation occurring in buildings: wind driven ventilation and buoyancy-driven ventilation. While wind is the main mechanism of wind driven ventilation, buoyancy-driven ventilation occurs as a result of the directional buoyancy force that results from temperature differences between the interior and exterior.[1]

Thermal mass is a concept in building design that describes how the mass of the building provides "inertia" against temperature fluctuations, sometimes known as the thermal flywheel effect.[1] For example, when outside temperatures are fluctuating throughout the day, a large thermal mass within the insulated portion of a house can serve to "flatten out" the daily temperature fluctuations, since the thermal mass will absorb thermal energy when the surroundings are higher in temperature than the mass, and give thermal energy back when the surroundings are cooler, without reaching thermal equilibrium. This is distinct from a material's insulative value, which reduces a building's thermal conductivity, allowing it to be heated or cooled relatively separate from the outside, or even just retain the occupants' thermal energy longer.

Scientifically, thermal mass is equivalent to thermal capacitance or heat capacity, the ability of a body to store thermal energy. It is typically referred to by the symbol Cth and measured in units of J/°C or J/K (which are equivalent). Thermal mass may also be used for bodies of water, machines or machine parts, living things, or any other structure or body in engineering or biology. In those contexts, the term "heat capacity" is typically used instead.