A recent study by the American Environmental Protection agency has identified indoor air quality as one of the top five urgent environmental risks to public health. The problem of indoor air pollution is largely avoidable through the implementation of sufficient ventilation, yet many of us continue to ignore the seriousness of the issue. We only seem to take notice when visible structural problems such as moisture and damp arise or when the health of the buildings occupants is seriously threatened.

It is hardly surprising that, as a people who spend up to 90% of our time indoors Irish people are almost constantly exposed to some form of indoor pollutant. Naturally occurring pollutants such as dust mites, fungus and mould thrive in Ireland, and rapidly occur when there is dampness in a structure and a relative humidity of or in excess of 70%. Something as essential as breathing and everyday functions such as cooking, bathing, dishwashing, and drying of clothes can create up to 5kg of moisture per day independently adding to an already humid indoor environment.

Health problem such as eye and throat allergies, asthma, headaches, tiredness, coughing, wheezing and even mental confusion can result from cases of high humidity. These problems are also triggered by unventilated residue, emanating from pets, dusty window coverings, bed linen, cigarette smoke and pollen. Further more, chemical sources of indoor pollution, as can be found in many building materials, paints, varnishes, electronic equipment, photocopiers and printers, cleaning fluids and polishes commonly cause head aches, breathing problems and allergies.

The impact of poor ventilation on a structure is likely to cause considerable damage over time, leading to problems such as excessive moisture, damp stains, smoke stains on structural surfaces build up of dirt, condensation and deterioration of décor. Though the results of some of these problems may initially seem only superficially detrimental, the long term effects can cause serious problems. It is costly to repair damage caused directly as a result of poor ventilation an dit can be dangerous to leave the problem untreated. Structures under the pressures of poor ventilation are prone to weakening and can prove unsafe as surfaces eventually rot and dilapidate.

The benefits of seeking advice from experts cannot be understated given the various criteria buildings are obliged to fill. In this regard, the most efficient and effective ventilation system, to suit the needs of a particular building, should be installed. It is also important to keep timber floors well ventilated, as this will prevent dampness and reduce energy consumption caused by irregular air flow. Loft ventilation and ventilation of appliances is also essential. Loft ventilation serves to diminish moisture build up in the ceiling while ventilation of appliances prevents the release of dangerous gases into the habitable environment.

The current building regulations for ventilation stresses the main functions of a ventilation system on a general level should: “provide an adequate supply of fresh air for using an area or building; achieve occasional rapid ventilation for dilution of pollutants and of moisture likely to produce condensation in habitable rooms, kitchens and room containing sanitary appliances; and extract moisture form areas such as kitchens and bathrooms, where it is produced in significant quantities.

In contrast to typical extract systems, mechanical supply systems work to deliver ventilation through the release of air taken from an uninhabited area of a structur. These systems are often used n existing buildings that suffer form condensation and are low in power usage, which ultimately makes these systems effective and energy efficient.

Finally mechanical ventilation systems with heat recovery (MHVR) differ from the other mechanical systems in that they are able to reclaim heat that would other wise be lost through the ventilation. MHVR’s take the heat from “wet” room and supply it to “dry” rooms. They control humidity and can be installed as a system for an entire building or instead as individual room units. MHVR’s are extremely effective, especially during winter months.

It is essential that the consumer talks to an expert prior to the installation of a system, in order to make the most of the system and conserve energy. Good ventilation is a fundamental requirement for a building to be fit for occupation and can play a vital role in securing the health of its occupants, the structure and ultimately the value of the building.

Ventilation Guidelines

Air flow rate: This is the air flow volume required to be extracted or supplied in to a room during a given period of time.

There are several ways to calculate the required air flow:

  1. Calculate the volume of the room.
  2. Multiply this by the number of air changes per hour (ACH) see tables below. The answer to this will give you the air flow required in metres cubed/hr (m³h)


Industrial Applications ACH
Welding areas 15-30
Laundries 30-60
Boiler rooms 20-30
Engine rooms 20-30
Factories and work shops 6
Foundries 30-60
Stores and warehouses 3-6
Paint shops 30-60
Dye works 10-15
Electroplasting shops 10-15
Commercial Applications ACH
Assembly rooms 4-8
Banks 3-4
Bakeries 20-30
Cafes 10-12
Canteens 5-10
Cinemas and Theatres 5-8
Conference and Board rooms 8-12
Dance Halls 6-8
Garages 6-8
Gymnasium 6-12
Hair dressing salons 10-15
Hospital sterilising wards 4-6
Commercial kitchens 15-30
Laboratories 8-12
Launderettes 15-30
Lavatories 8-15
Libraries 3-5
Offices 4-8
Photo and x ray darkrooms 10-15
Recording studios 10-12
Restaurants 6-10
Schoolrooms 2-4

All these values must not take the place of any regulation requirements and can be modified for each particular application.