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Indoor environmental quality (sometimes abbreviated to IAQ) refers to the quality of the air in a building environment. Research has shown that building-related symptoms are associated with building characteristics, including dampness, cleanliness and ventilation. Voltimum UK managing editor James Hunt introduces the topic of this VoltiTECH here:
Therefore, IAQ - in combination with energy saving and emissions reducing activities - has become an increasingly important health and safety issue. Energy saving measures have resulted in modern airtight buildings that can easily create IAQ problems. Such problems result from interactions between building materials and furnishings, in-building activities and external climate. They include the following causes:
- Indoor environment - temperature that is too low, excessive humidity and noise, plus certain lighting issues.
- Indoor air contaminants - chemicals, dusts, moulds or fungi, bacteria, gases/vapours and unpleasant smells.
- Outdoor environment - Radon gas.
- Insufficient outdoor air intake.
Examples of common indoor air contaminants include:
- From building materials - Dusts, glassfibre, asbestos and gases (often formaldehyde).
- From building occupants - Carbon dioxide (CO2), tobacco smoke, body odours, perfumes.
- Off-gas emissions from furniture, carpets and paints - Gases (again, often formaldehyde), vapours and odours.
- From carpets, fabrics and cushions - Dust mites.
- From damp areas - Microbial contaminants, fungi, moulds and bacteria.
- From workplaces - Toxic gases, volatile organic compounds (VOCs) cleansers, solvents, pesticides, disinfectants and adhesives.
- From PCs, peripherals, electric motors, electrostatic air cleaners - Ozone.
Possible health effects:
Occupants of bad IAQ buildings may suffer what is often termed 'Sick Building Syndrome' (SBS), which may comprise a wide range of health problems. The many possible resulting symptoms may include dizziness and nausea, coughing and sneezing, dryness and irritation of the eyes, nose, throat and skin, headache, fatigue, shortness of breath, hypersensitivity and allergies, plus sinus congestion.
Mitigation:
Traditionally (and still), heating, ventilation and air-conditioning (HVAC) techniques are used to mitigate some of these health effects. One aspect today is to reduce energy consumption while maintaining adequate air quality using demand controlled ventilation. Rather than setting throughput at a fixed air replacement rate, CO2 sensors dynamically control the rate, based on the actual building emissions.
Ventilation systems:
Often, installed ventilation systems minimise the amount of fresh air entering and circulating within the building. This unfortunately can allow a build-up of air contaminants within the building, which is hardly ideal, although use of air filters can trap some air pollutants.
Moisture management and humidity control requires operating HVAC systems as designed, but this may adversely affect efforts to try to optimise energy conservation. Commercial buildings, and sometimes residential too, are often kept under slightly-positive air pressure relative to the outdoors to reduce infiltration. Limiting infiltration helps with moisture management and humidity control.
For more information about air-conditioning, see the article entitled 'Air conditioning develops for higher efficiencies' elsewhere in this VoltiTECH.
More work to do:
The above is the background to legislation designed to ensure healthy indoor air quality in tomorrow's new homes, especially as improvements to Building Regulations Part L require new homes to be built to increasing standards of airtightness, which could affect health - the tighter the buildings are getting the more purpose-provided ventilation is needed.
The Zero Carbon Hub Ventilation & Indoor Air Quality (VIAQ) Task Group concluded the first phase of its work with the publication of 'Mechanical ventilation with heat recovery in new homes - interim report'.
The VIAQ Task Group, chaired by Lynne Sullivan OBE, comprises of a broad cross-section of industry practitioners and academics and was set up to review the existing evidence around indoor air quality and consider the associated issues in detail.
As improvements to Part L require new homes to be built to increasing standards of airtightness, minor gaps in the building fabric no longer contribute significantly to ventilation. As a result, occupiers are becoming wholly dependent on the effectiveness of the installed ventilation system to maintain good indoor air quality.
It is commonly accepted across the industry that mechanical ventilation with heat recovery (MVHR) will grow to become the dominant installed ventilation system because of its ability to recover heat from the exhaust air and contribute to carbon savings. However, evidence from the UK, Europe and various other countries reviewed by the Task Group has identified a number of issues with these systems that need to be addressed as a priority.
The Task Group's interim report recommends that MVHR practice must change substantially to ensure that systems are designed, installed and commissioned correctly. It also points to the importance of fully taking into account the needs of the consumer in good system design, providing appropriate controls and making sure that there are proper arrangements for ongoing maintenance.
Neil Smith, NHBC's Group Research & Innovation Manager and secretary to the VIAQ group, said: "The interim report brings together useful evidence from a number of studies and highlights some key concerns that must be addressed as a matter of priority. Clearly it is imperative that in our pursuit of higher energy efficiency standards, new homes continue to provide healthy indoor environments and there is no risk to occupant health from changes in building practice."
The work of the Task Group is expected to conclude later this year and will take into account monitoring of a number of occupied homes with MVHR that are currently being monitored.
The interim report, this is now available to download from www.zerocarbonhub.org and www.nhbcfoundation.org.
For more information on surge arrestors, go to other parts of this VoltiTECH.