Coleman Diagnostics
Indoor Air Quality Assessment &
Psychrometric Calculator
INDOOR AIR QUALITY MATRIX
How the IAQ Matrix Works
The Indoor Air Quality Matrix was developed around industry guidelines and other accepted parameters of internal temperature, humidity and vapour pressure. In addition, the App factors the differential vapour pressure between the internal and external environment which is useful when evaluating the performance of a buildings ventilation.
Guidance on the parameters used to develop the matrix are published in the following documents and details on these parameters can be viewed in the Psychrometric Calculator.
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Public Health England – Protecting and improving the Nation’s health 2014
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World Health Organisation (WHO) guidelines for indoor air quality: dampness and mould
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British Standard 5250:2021 Management of moisture in buildings – Code of Practice
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British Research Establishment (BRE) Understanding dampness 2004
Internal Air Quality Matrix
The Air Quality Matrix presents results in an easy to interpret points score system (<6 poor - >13 Excellent) with colour coded traffic light array red (poor) – green (good). The Matrix provides a IAQ Score out of ‘15’ and presents variances of the results that can be achieved by simply manipulating the internal ambient conditions, these are presented in the ‘Ambient Internal Relative Humidity’ matrix and the ‘Surface Relative Humidity Change’ matrix.
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You can view the IAQ Matrix by clicking the 'Show IAQ Matrices' at the bottom of the 'IAQ Results' page
Mould Risk to Surface
The IAQ Matrix also assesses the ‘Risk to Mould’ based on the calculated measurement of relative humidity at the surface. This is scored out of ‘5’ with ‘1’ being a 'High risk' to mould >90% RH and ‘5’ being a 'No risk' to mould <60% RH at the surface.
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The Smart Matrices are the easiest way to determine if a problem exists
How to use the smart 'Ambient Internal Relative Humidity' matrix
In the smart ‘Ambient Relative Humidity’ Matrix the APP effectively interprets the data into actual ‘conditions’ should there be a change in ambient temperature and provides new results on this basis.
The ‘Ambient Internal Relative Humidity’ Matrix is designed around fixed parameters between 15 - 24°C. The APP uses the data input and adjusts the relative humidity based on a change in temperature within the building. This is beneficial as it allows you to instantly see the influence of temperature change to help determine if a property has an issue with high humidity or simply temperature.
For example: Input parameters 16°c @ 70% RH =IAQ Score Temp. = 3 (Fair) / RH% = 2 (Poor)
By using the ‘Ambient Internal Relative Humidity’ Matrix, you can quickly see changes to the internal relative humidity in response to temperature changes. In this scenario, a simple increase in temperature from 16°c to 20°c significantly reduces the internal relative humidity to an acceptable level at 54.4% RH. Therefore, in the above scenario, the problem wasn’t related to high humidity, it was after all a temperature related problem.
The new IAQ Score with the changes calculated @ 20°c at 54.4% RH show a much improved IAQ Score= Temp. = 5 (Excellent) / Relative Humidity = 4 (Good)
New IAQ Score using the Smart 'Ambient Internal Relative Humidity' Matrix
How to use the smart 'Surface Relative Humidity Change' matrix
In the smart ‘Surface Relative Humidity Change’ Matrix the APP re-calculates the surface relative humidity in relation to changes in surface temperature. The Matrix calculates the change in Surface RH +5°c / -5°c from the Input Surface Temperature. This allows you quickly see the influence of improvements to surface temperature and recalculate the 'Mould Risk to Surface' Score.
Improvements to the surface temperature can usually be made by; increasing the ambient air temperature thus influencing the temperature of surrounding surfaces or by insulation improvements.
For example: Input parameters Temp 21°c @ 60% RH, ST 15°c
= IAQ Score Temp = 5 (Excellent), RH% = 4 (Good), Mould Risk = 2 (Moderate)
Calculations for the Surface RH used to provide the 'Mould Risk' Score can be found in the Psychrometric data (87.5% RH @ Surface)
IAQM & Mould Risk to Surface Results
By using the smart ‘Surface Relative Humidity Change’ Matrix an improvement to the surface temperature by just + 3°c (15°c - 18°c) would reduce the relative humidity at the surface to a 'Low Risk', Score 3 of 72.3% RH.
Smart 'Surface Relative Humidity' Matrix
Mould Risk to Surface Score
The smart ‘Mould Risk to Surface’ Matrix uses the calculated relative humidity at the surface and provides a points based score and traffic light array on the ‘Risk’ to mould based upon widely accepted parameters. This is scored out of ‘5’ with ‘1’ being a 'High risk' to mould >90% RH and ‘5’ being a 'No risk' to mould <60% RH at the surface. Some moulds species (‘primary colonisers’) will germinate on some substrates when exposed to conditions of 75-80% relative humidity relatively rapidly; as the relative humidity against the surface increases so does the risk to mould growth (‘secondary’ and ‘tertiary’ colonising moulds).
Mould Risk to Surface Matrix
