25 June 2020

Ventilation in the built environment has long been recognised as important. In fact, since ancient times there have been observations and attempted solutions for improving the quality and circulation of indoor air.

We have moved significantly from the times when simply creating vents in a building were the only way to deal with ventilation issues, although vents are still relevant. Over the last few decades there have been considerable developments in ventilation technology, the latest being the evolution of decentralised Mechanical Extraction Systems (dMEV).

In this blog we’ll be looking at how ventilation technology has developed and in particular the arrival of dMEV. Let’s start at the beginning.

A potted history of building ventilation

The impact of bad indoor air has been considered since humans started using fires indoors. Homes in ancient Rome had cracks and holes in the roof to allow smoke to move outside. In ancient Egypt it was recognised that stone carvers suffered worse respiratory problems when they worked indoors.

Chimneys became widespread in the 11th and 12th centuries in order to improve the quality of air indoors. They were designed in particular to alleviate smoke and dust from open fires. But many were inadequate and as a result there were a number of deaths due to carbon-monoxide poisoning.

As early as the 17th century, home ventilation has been on the public agenda. In 1631, King Charles I decreed that British homes must have 10-ft high ceilings and taller windows to facilitate better ventilation.

During the Industrial Revolution many physicians believed pollution to be responsible for a wide range of chronic health conditions. This included air quality inside and outside the home. Building ventilation started to creep further up the public health agenda.

In 1835, when the British Houses of Parliament were rebuilt after it was destroyed by fire, a ventilation system was added. Designed by David Boswell Reid, Physician, Chemist and Engineer, it was the first ventilation system of its kind in the world.

In the early 19th century the development of electric powered fans helped to facilitate the movement of air indoors. It was the beginning of the use of mechanical methods to help regulate temperature and airflow in homes and public buildings.

Ventilation has become increasingly important, both in new building development and in old buildings. In fact, ventilation in old buildings is of particular concern as their structure relies on sufficient airflow throughout.

So, what are the modern ventilation issues and how has dMEV technology developed?

A wind of change in ventilation technology

Ventilation is largely about health and air quality and as housing standards have improved, it has become an integral part of the building process. Methods to provide suitable ventilation have advanced alongside the developments in building techniques.

While there are clear links between poor ventilation and ill-health, modern airtight housing standards and our evolving demand for comfort and warmth (blocking trickle vents and keeping windows closed) are an increasing cause for concern.

Without adequate ventilation, it is now recognised that homes can become toxic boxes of harmful chemicals and have a propensity for the build-up of moisture. The development of mould in poor housing is one of the now known consequences of inadequate ventilation.

Bathroom and kitchen extractor fans and trickle vents in windows when used in isolation as a ventilation system are simply not sufficient as they don’t address ventilation in all rooms.

Back in 2016, the BBC warned of the health risk associated with airtight homes. The introduction of Part F to Building Regulations in 1995, with subsequent amendments in 2006, 2010 and 2013, seeks to address ventilation issues in the built environment, but emphasises that ventilation needs to be controlled so that it doesn’t have an adverse effect on the energy performance of the building.

A new consultation document setting out plans for the Future Homes Standard, proposes options to increase the energy efficiency requirements for new homes in 2020, but also addresses the need for changes to Part F in terms of ventilation.

Following a government study of 80 homes in the period from November 2015 to February 2016 across seven developments in England, it was found that few homes actually met the minimum ventilation provisions for both extract fan flowrates and trickle ventilator area in line with the guidance in the 2010 edition of Approved Document F (ADF).

Mechanical ventilation has become an essential part of building strategy and its technology has developed significantly in recent years. Whole house ventilation (MVHR – Mechanical Ventilation with Heat Recovery) is being installed into new homes, but is trickier to retrofit into older homes largely because of the duct work required which may cause damage to the fabric of the building.

Without a doubt, new technological advancements are offering a solution to resolve indoor air quality issues and combat mould. Continually running ventilation systems are, as a result, becoming commonplace. The latest of these developments is dMEV.

Different types of ventilation

There are several types of building ventilation including:

  • A positive pressure system that blows outside air into the building
  • A vacuum system (negative pressure) that extracts stale air from a building
  • A balanced inlet and outlet system that uses inlet and extractor fans to keep internal air pressure similar to that outside
  • Local extractor systems that extract at source, such as cooker hoods and fume cupboards

Mechanical ventilation systems work by extracting stale air and/or supplying fresh air into the rooms in a flat, house or building. There are four main types of continuous mechanical ventilation. These are:

  • MVHR – Mechanical Ventilation with Heat Recovery
  • MEV – Mechanical Extraction Ventilation
  • dMEV – decentralised Mechanical Extraction System
  • System 1 – Background Ventilators and Intermittent Extract Fans

What exactly is dMEV technology?

dMEV is a form of continuous ventilation used in the built environment. It is a low-energy ventilation system designed to replace noisy and inefficient conventional bathroom extractor fans.

This technology has become popular within the social housing sector and with private landlords due to its cost-effectiveness and the fact that it requires no input from residents once installed. dMEV fans run continually at a low trickle rate, boosting automatically when moisture levels rise, for example when cooking, taking a shower or running a bath.

dMEV systems work in the same way as whole house Mechanical Extract Ventilation (MEV) but with individual fans installed in specific rooms, usually the kitchen and every wet room in the property. The system meets all of the building regulation ventilation guidelines, is easy to install and has a low-running cost.

The evolution of Greenwood’s dMEV

Greenwood has a longstanding history of innovation. Since launching the first continuously running dMEV fan in 2007, the product (Unity CV100) was further developed to offer more energy-efficient components and improved airflow performance. The product development also provided Guaranteed Installed Performance (GiP) to ensure Building Regulation compliance, leading to the launch of the Unity CV2 in 2010.

Unlike the CV100, which incorporated a fixed running speed, the CV2 offered a variable motor to ensure correct ventilation could be consistently achieved. The CV2 also introduced semi-rigid ductwork – a first for the market – making it much quicker and easier to install.

In 2017 the CV3 dMEV fan was released, an evolution of the CV2 with additional enhanced product features, including noise reduction and improved airflow performance. The product development included a night-time mode to prevent nuisance running noise at night. The Unity CV3 also offers technological advancements providing real-time data when required and is the first system of its kind in the world.

Both the CV2 and the CV3 have HumidiSMART™ (SMART Technology) incorporated into the product – a revolutionary way of using humidity levels to provide effective ventilation in domestic properties. In contrast to traditional humidity sensors that activate because a pre-set threshold is crossed, Greenwood HumidiSMART™ only reacts to man-made increases ensuring the fan only boosts when required.

Greenwood’s Unity dMEV CV3 offers running levels as low as 14.5 dB (min) and costs less than £1 to run for the entire year, which is considerably less than other comparable products in the market.

What does the future of ventilation look like?

Effective energy-efficient ventilation is now an essential element in the design and construction of all buildings. This is especially important now that the focus on the built environment is on energy efficiency and the well-being of its occupants.

The demand for better insulated homes has prompted a different approach to ventilation. dMEV is a the modern day ventilation solution that addresses a number of issues, from ease of install to energy efficiency and cost effectiveness. Best of all it doesn’t rely on residents to operate.

The effects of climate change on the indoor environment are present challenges for public health. Innovation will lead the way in keeping indoor air quality safe.