The need for mechanical ventilation

There are several ways to bring fresh air into the buildings - using mechanical equipment. Ventilation can be mechanical (using mechanical equipment) or hybrid, also known as mixed-mode (a combination of the previous two).

Types of mechanical ventilation

Mechanical ventilation is the intentional fan driven flow of outdoor air into a building. Mechanical ventilation is often provided by equipment that is also used to heat and cool a space.

Hybrid (or mixed-mode) ventilation that combines natural ventilation and powered ventilation. This process allows for greater responsiveness to external conditions whiles keeping the space comfortable throughout the day and in different seasons.

Requirements for mechanical ventilation

From the viewpoint of working conditions & comfortable living, good and efficient ventilation should meet various functional requirements — all based on various parameters and control systems. However, we need to always ensure an efficient, continuous and accurate of ventilating a building.

Designing a ventilation system

When choosing/designing a ventilation system, factors to consider include but are not limited to:

Type of building/structure
Location of building and outdoor climate
Usage of the space
Volume of the area
Number of airflow changes required per 24 hours
How exhaust air will be vented
Structural requirements and availabilities, electrical requirements and availabilities
Budget available

Rate of supply of fresh air

The quantity of fresh air to be supplied to a room depending on the use of a building. The rate of supplying fresh air is decided by considering several factors such as a number of occupants, type of work, period of working, the age of occupants, etc.

Air movement (or air changes)

Air has to be moved or changed to cause proper ventilation of the space. The rate of air change depends on the number of persons inside, room temperature, nature of the work, different room categories, and activities, etc.

Air characteristics

It is desirable that the incoming air for ventilation should be cool in summer and be warm in winter — before it enters the room.
Also the velocity of air is very important, including ventilation strategy, distribution pattern, etc.
The air contains certain amount of humidity.
Air quality plays a significant role in the comfort of people affected by a ventilation system.

Fundamentals of mechanical ventilation

Mechanical ventilation is one of the systems that keeps a habitable environment.

Purpose of mechanical ventilation:

To heat or cool the incoming air.
To circulate/move the air in a room.
To supply/exhaust the required air amount in the room.

Basic information about mechanical ventilation:

Ventilation is operable independent on exterior conditions.
Requires precise operation control.
Provides temperature and humidity (and other sources) control.

Mechanical ventilation is based on pressure difference and caused by dynamic pressure of a mechanical device — fan/blower.

Ventilation consists of 3 main parts:

Ventilation rate — the amount and quality of the outdoor air.
Airflow direction — the flow of air within a building, from 'clean' to 'dirty' areas.
Air distribution — the delivery of outside air and removal of pollutants.

Basic principles of mechanical ventilation:

Overpressure ventilation
Balanced ventilation
Underpressure ventilation

Mechanical ventilation consists of several parts, i.e. air handling unit (AHU), ducts, air supply/exhaust devices, dampers, fan coils, heating/cooling unit, etc.

Centralised or decentralised systems

It highly depends on the system and the building.

Centralized system as a single ventilation system for larger buildings, family houses, small offices, etc. Lower energy consumption thanks to central controls based on constinuous monitoring of indoor air quality.

Decentralized system is ideal for smaller projects, such as kitchen, bathroom or toilet renovations or home extensions.

Important terminology used in ventilation

NV, MV and MM

Natural ventilation (NV) is driven by pressure differences between one part of a building and another, or pressure differences between the inside and outside.

Mechanical (or forced) ventilation (MV) is driven by fans or other mechanical equipment.

Hybrid or mixed mode ventilation (MM), hybrid ventilation systems involve natural ventilation supplemented by mechanical systems to ensure minimal background ventilation. Often involves certain architecture features such as ventilation stacks, chimneys, shafts or cowls, atria spaces or light wells and wind catchers, cowls or scoops, which may or may not involve some automation.

ACH

HVACR

IAQ and IEQ

Indoor air quality (IAQ) refers to the air quality within and around buildings and structures, especially as it relates to the health and comfort of building occupants. Understanding and controlling common pollutants indoors can help reduce your risk of indoor health concerns.

Indoor environmental quality (IEQ) refers to the quality of a building's environment in relation to the health and wellbeing of those who occupy space within it. IEQ is determined by many factors, including lighting, air quality, and damp conditions.

CAV, VAV and DCV

CAV – Constant Air Volume — Simple method for controlling usually temperature and humidity, using high airflows and high air volumes. Simple method for constant airflow, typically could be only switched on or off.

VAV – Variable Air Volume — The most basic demand-control for ventilation system — allows the airflow to be varied during service hours and can be adjusted in response to factors such as temperature or air quality.

DCV – Demand Controlled Ventilation — Advanced demand-controlled ventilation — adjusts the airflow and temperature in response to demand and occupancy status in rooms/spaces to cater for differing uses.

A mechanical ventilation system strikes the perfect balance — the demand-driven system ventilates only where and when it needs to, saving energy along the way. And you get to enjoy fresh indoor air at all times.

You need to allow cookies for marketing if you want to view this type of content

Watch: Visualising the invisible — Ventilation

Lecturers: Åsa Norén-Lundh & Caroline Jacobsson

Webinar recording from Swegon Air Academy, 2022.

In this video you will learn all about ventilation, meeting demands for both comfort and sustainability targets, and keeping a good energy efficiency.

What are the key technical ventilation principles?
What is air exchange and why it is important?
What is energy exchange and how can we improve it?
How can we increase comfort, efficiency, and wellbeing through various methods of ventilation?

CAV, VAV and DCV

To minimise energy consumption of the building, ventilation technology evolves over the years upgrading the HVAC systems from the constant air volume (CAV) to variable air volume (VAV) to a more advanced system called demand-controlled ventilation (DCV). From a system that handles continuously the whole air volume (CAV) to a system that handles the strictly demanded air volume (DCV) which ensures a good indoor air quality including thermal and acoustic comfort inside a building.

HVAC system can be categorized into two types:

Constant air volume (CAV) — ventilation with constant airflow controlled by chronological management (e.g. ON/OFF) or control of supply/extract temperatures (and often also humidity control).
Variable air volume (VAV) — the control is managed in a manual or continuous mode with prefixed models or time steps.
Demand-controlled ventilation (DCV) system is designed with the aim of supply a quantity of fresh air fitted with the need in every situation, ensuring the right quantity of fresh airflow and right environmental conditions in terms of relative humidity and temperature.

Demand-controlled ventilation — Case study on comfort and energy

The purpose of a heating, ventilation and air conditioning (HVAC) system is to provide continuously the best indoor environmental conditions (IEQ) in terms of temperature and relative humidity at the lowest energy costs as possible. Using advanced simulation tools, different types of HVAC systems can be evaluated, such as a constant air volume (CAV), a variable air volume (VAV) and a demand-controlled ventilation (DCV). The goal si to evaluate the energy saving, economic advantages (payback time) for different solutions.

Download our Research 'Demand-controlled ventilation — Case study on comfort and energy'

Download AIR by Swegon Air Academy

The aim of the book is to provide insights into the factors and circumstances, that significantly influence the creation of good indoor climates and energy-efficient ventilation solutions. The contributing authors were chosen among national and international experts. The chapters have been written at a popular science level so readers can readily understand the content and make their own decisions.

The book has over 600 pages and is divided into five sections: Ventilare necesse est, Economic and social responsibility, Energy and the outdoor environment, Indoor environment in a wider sense, and Air handling processes and the indoor climate.

Download the book AIR Swegon Air Academy

#ventilation

More about ventilation

If you are interested in more knowledge related to ventilation, here are some interesting readings for you:

Check out more references & bibliography

A well-ventilated home or building is important for the health and comfort of those who live in them, as well as longevity of the structure itself. There are several options how to ventilate, natural, mechanical or a combination. You just need to choose a good system for you and your building.

Anonymous

Go back to 'Ventilation: Why, where, when & how'