/ Technical Topics

All you need to know about ventilation & indoor air quality

Indoor Air and People’s Health

Air is the mixture of gases that we breathe, which is all around us and in our lungs at all times. Air at habitable altitudes contains between about 1-5% water vapour, depending on weather and altitude. Completely dry air is found only in a laboratory, although some badly designed and built buildings contain air that is too dry to be healthy for people.

If all the water vapour is removed from air, the remaining air is about 78% nitrogen (N2), 21% oxygen (O2) and the remaining 1% of dry air is a mixture of other gases.

Air can be easily contaminated with dust particles. Organic dust is also food for mould.

Poor Ventilation and Consequences – Mould & Condensation

We spend a huge part of our lives indoors. Human activity creates a lot of moisture, especially in houses. Washing, cooking and drying clothes all generate moisture in the air. A typical household can generate 12 litres of liquid per day. If your house or office isn’t well ventilated the moisture will sit in the air and the Relative Humidity levels of the space will increase.

Optimum Relative Humidity Ranges for Health

A 50% humidity level is optimum for humans. Above 70% humidity and we start to suffer from issues related to mould, bacteria, and mildew in the air such as asthma, respiratory problems, sore throats and noses, allergies etc. This gets progressively worse as RH increases.

Air movement through buildings

Air moves both heat and water vapour, both of which are important to people’s health and comfort.

Air movement through any container, including a building, requires an opening for air to enter, an opening for air to leave, and energy to create a pressure difference to move the air. The size and location of the openings and the amount of pressure difference all determine how much air will move through the container.

The building envelope significantly impact the performance of the ventilation system

Buildings have holes, gaps in them – some intentional, some not. Air moves through those holes – the amount of ‘unplanned’ leakage can vary depending on dwelling exposure, and pressure differences. There is no need for any intentional air leaks, through a building. Zero air leakage is a suitable target. The ability to move the right amount of air through the right parts of a building at the right time is possible by building tight, then controlling the air pressure fluctuations (ventilation).

Designing and building a good enclosure is the primary way to keep a house comfortable, safe, as well as durable and energy-efficient.

If you’re building or renovating to Passive House, nZEB or LEED standards and you and your contractor are working hard to make sure the airtightness is perfect, the next step is to ensure that it is properly ventilated. Providing healthy indoor air quality is a non-negotiable part of the process.

You will need a smart and properly designed ventilation system in order to supply and control the fresh air you need to breathe. This control allows you to have filtered, fresh air while also extracting air with higher CO2, humidity and unwanted VOC’s.

All buildings that people spend a significant amount of time (houses, apartments, schools, building offices) should be ventilated by choosing a ventilation system that works effectively for that particular building.

A True Ventilation System Moves Stale Air Out of a Building and Supplies Only Fresh Outdoor Air

Adequate and effective ventilation shall be achieved by:

  • limiting the moisture content of the air within the building so that it does not contribute to condensation and mould growth
  • limiting the concentration of harmful pollutants in the air within the building.

As buildings are becoming more energy-efficient the rates of natural (and ‘unplanned’) ventilation are decreasing. This means that nowadays a mechanical ventilation system is crucial – in particular as people spend more time indoors.

Which system to choose depends on a building’s specific needs, but there are some fundamental principles that allow you to achieve the right ventilation.

         1. Ventilation that meets the latest Building Regulations

The ventilation system needs to comply with the latest applicable standard such as Part F for UK/IRL or ASHRAE for the USA, for each building type – residential and non-residential constructions, and to be highly energy efficient.

Ireland and the UK

Residential Buildings

Ventilation systems should provide 0.3l/s/m2 or 5l/s per person +5l/s whichever is greater – the general ventilation rate. The ventilation system should also have an allowance for an extract rate of 13, 8, or 6l/s depending on the class of the wet room. The system should also have a capacity of 25% over the general ventilation rate. This overcapacity ensures that the system is not always at capacity.

Non-Residential Buildings require ongoing air renewal by the ventilation system. The rate of ventilation depends on the number of occupants and how the building is being used.


Most building codes rely on the *ASHRAE standard 62.1 and 62.2 to establish ventilation system design and acceptable indoor air quality.

2. Ventilation adapted to the climate conditions

In areas where the indoor humidity gets high during the winter because of unusual indoor moisture sources, or because of a climate where outdoor air is humid during the winter, an energy-efficient heat recovery ventilation it’s a better choice due to the fact that it will reduce winter indoor humidity levels. Also in a warm and hot climate, the HRV is recommended to be installed.

         3. Keep it Simple

The more complicated a ventilation system is, the most likely it will be vulnerable to problems.

Why Decentralised Ventilation?

One of the most obvious benefits is that it avoids the need for extensive, expensive and potentially complicated ductwork, susceptible to collecting dirt, grime and other pollutants. No ductwork means less maintenance work. Also, dropped ceilings and central units can be avoided, incurring a saving in terms of both cost and space.

Decentralised ventilation is customisable, very flexible, easy to install and scalable – it does not have to installed all at once.

The LUNOS decentralised ventilation supplied by Partel is based on a modular control system, developed for every individual space of the building, and it can be combined into three different ventilation systems: exhaust air system, hybrid system, and system with heat recovery.

The correct system depends on the individual requirements of the project and the habits of occupants.

         4. Quality is fundamental

In order for a low-energy building or Passive House to perform as designed, quality needs to be prioritised at every step of the planning and construction process. In this way, the building owner gets what has been promised. Using integrated and high-performance ventilation systems, offer further security in the design of highly efficient buildings, and fresh air for generations.

Mechanical Ventilation with Heat Recovery – More Comfort. Less Energy.

In balanced mechanical ventilation systems, two air streams are driven by a supply fan and an exhaust fan. An air-to-air heat exchanger connects the two streams and transfers heat from the warm air stream to the cold air stream with little or no mixing. LUNOS systems are innovative and use a recuperating system where by patented parts allow Lunos to capture warm air during a 70 second extract cycle in a ceramic core and then transfer the stored heat to the cool incoming fresh air.


  • Recover heat energy otherwise lost to the outside, making for a more cost-effective, energy-efficient, environmentally conscious house;
  • Prevent condensation and mould…and the potential subsequent deterioration of the building fabric and potential health risks to occupants;
  • Improve air quality, removing pollutants such as CO2, VOCs, Radon, Dust, & Pollen, making for a more comfortable living space.

How LUNOS MVHR system work?

LUNOS ventilation systems are based on airflow through the entire living areas, are compliant with specific requirements and operate in accordance with the parameters of humidity and temperature. The airflow level increases or decreases depending on the exhaust air humidity. In this way, there is always as much ventilation as necessary and as little as possible.

Controlled home ventilation

Coming in:
– fresh, filtered air
Going out:
– moist and odour-loaded air from kitchen, bathroom, utility rooms etc.

contaminants and gas release from paints, carpets, furniture etc.
Stays inside:
Stays outside:
– suspended particles and insects (via filter inserts)

noise (via sound-absorbing outer wall elements)

wind (via wind pressure relief at the outer wall elements)

Comparison of unregulated ventilation with a model of heat recovery in a detached house

Result of the calculation:

By using the LUNOS e2 in combination with the exhaust fan LUNOS RA 15-60, the heating load is reduced by 15 %. The ventilation heat loss is reduced to 43 % (57 % savings). The heating load calculation is usually performed by a specialist planner, who can calculate how much the owner can save per year based on the percentage savings.

Ventilation systems should be installed in every new build and energy retrofit. The reduced levels of indoor air pollution are reason enough to invest in a good ventilation system. The costs of such systems, indeed, result in extra construction expenses. In most climates, ensuring that the system comes with highly efficient heat recovery means that some of these investment costs can be regained in the form of energy savings throughout the building lifecycle.

LUNOS Ventilation with Heat Recovery Range


Our Certified Passive House Designers and Consultants have the knowledge necessary to ensure you quality in the lead-up to building construction.

Take a step towards an energy-efficient building. Get in touch with Partel Technical Support team and decide together which solution may be best for your project needs.



Henry Gifford, Buildings Don’t Lie, Energy Saving Press LLC, 2017



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