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Interpreting IAQ the Results

Temperature: Low IAQ Score
Diagnosis: Low internal temperature

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Work through the following checklist to determine the cause:

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  • Is the heating system suitable for the property?

  • Is the heating system being used sufficiently to create a suitable internal environment?

  • How is the heating system controlled room thermostats or user defined? If user defind how often is the heating used?

  • Are the heating appliances sized appropriately for the rooms?

  • Are the heating appliances appropriately located within the rooms?

  • Are the radiator vavles open?

  • Are additional heating methods being used to help achieve a suitable internal environment?

Humidity: Low IAQ Score
Diagnosis: High internal humidity

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Work through the following checklist to determine the cause:

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  • Is the ventilation adequate, is the ventilation system suitable, does the property have adequate means of both natural and mechanical ventilation where required?

  • Are the number of occupants suitable for the size of the property (overcrowding)?

  • Where extractor fans are present are these working efficiently. Note: A specialist vane anemometer should be used to evaluate the performance (rate of air flow) of fans. Fan performance guidelines can be obtained by referring to the Building Regulations approved Document F (UK only).

  • Do the fans incorporate timer over runs / humidistat functions?

  • How is the ventilation operated, is it user defined switches/pull chords or automatic (constantly operational)?

  • Are the fans positioned in a suitable location?

  • Is the fan exhaust suitably ducted to atmosphere and unrestricted?

  • If natural background ventilation is provided via means of air bricks/trickle vents are these free and open to atmosphere and do they conform to the requirements for the level of occupation? The requirements for background ventilation can be obtained by referring to the Building Regulations approved Document F (UK only).

  • Is there sufficient undercuts beneath doors to allow air flow between rooms?

Vapour Pressure Excess: Low IAQ Score
Diagnosis: High internal humidity, low external vapour pressure 

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Work through the following checklist to determine the cause:

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  • See above checklist for High internal humidity

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  • The 'Vapour Pressure Excess' is the difference in vapour pressure between the internal and external environments. The vapour pressure internally is the sum of the external + indoor atmospheric moisture levels. By measuring and removing the external level we are left only with the measurement of indoor moisture production, this is presented as vapour pressure excess and reflects the moisture solely produced through occupation. Excess Vapour Pressure is a good measure of ventilation.

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*Its important to mention that a 'Low' Vapour Pressure Excess Score can occur in extreme conditions during the cooler winter months when the external temperature and vapour pressure falls significantly, thus resulting in a higher than normal differential to the internal environment. In such circumstances, an assessment of the internal relative humidity can provide a much more accurate and balanced overview. *

Mould Risk to Surface: Low IAQ Score
Diagnosis: Low ambient temperature, low surface temperature

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A ‘Low' IAQ Score in the 'Risk to Surface Mould' matrix indicates a problem with humidity at the surface caused by either, a low ambient temperature, high internal humidity or low surface temperature. The Surface Relative Humidity conditions are calculated in the App and are presented it the Psychrometric data (Surface RH%).

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It is important to mention, the longer the duration of exposure at the surface the greater the risk. Some moulds can germinate when exposed to conditions above 75% relative humidity for relatively short periods, but other factors such as the surface materials are important.

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  • Are the surface temperatures comparable to the internal temperature (usually within 2 – 3°C and above)

  • Are there any obstructions to the surfaces caused by adjacent furnishings, long draped curtains etc, (restricted surfaces are colder, thus greater potential for mould and condensation)

  • Is the surface suitably insulated?

  • Are there any deficiencies within the insulation (further thermographic / intrusive borescope investigations maybe required)?

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After the first assessment any recommendations shown above should now be made followed by any required improvements.

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Find out how to use the smart ‘Ambient Internal Relative Humidity’ matrix and the smart ‘Surface Relative Humidity Change’ matrix.

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