High-efficiency housing monitoring

March 2020

A high-efficiency house ensures minimum energy demand, but is the air quality equally guaranteed? Health and innovation go hand in hand, just as energy efficiency and a healthy indoor environment must go hand in hand.

In this first case study, we present an example where, thanks to indoor air quality monitoring, a significant concentration of pollutants was detected for a healthy space. And thanks to this, guidelines for improvement were given. Because what is not measured cannot be improved.

Description of the place:

  • Type of space: Energy-efficient 80 m2 house completely refurbished in an existing residential building.
  • Situation: Sixth floor of a building with west-east orientation (main façade, kitchen and master bedroom to the west, the rest of the bedrooms to the inner courtyard with east orientation).
  • Energy efficiency: High energy efficiency criteria of the passivhaus standard (not certified). Tightness test n50, 0.38 renov/hour.
  • Ventilation: Double flow mechanical ventilation system with heat recovery.
  • Heating: Underfloor heating system.
  • Other: Recycled cotton interior insulation , plasterboard interior partitions and laminated flooring with white lacquered MDF skirting board.

Measurement and analysis:

After several weeks of monitoring, continuously high levels of formaldehyde indoors, with peaks reaching 1,000 µg/m3 and a daily average of over 150 µg/m3. The values recommended by the WHO should not exceed 100 µg/m3, and according to the technical measurement standard in baubiologie SBM2015 for sleeping areas, values above 100 µg/m3 are already extremely significant.

Despite having a double-flow mechanical ventilation system with heat recovery, it is not able to reduce formaldehyde peaks, while manual ventilation with windows does. CO₂ concentration is maintained at comfort levels 65% of the time.

As a complement to the monitoring through the MICA device, samples are taken for analysis in the laboratory to complement the information monitored. Samples of both formaldehyde and VOC screening.

From this information, significant concentrations of both formaldehyde and specific volatile organic compounds are confirmed: ethyl acetate or cyclohexane, irritant and neurotoxic compounds, mainly used as adhesives.


The cross-reaction of the electrochemical formaldehyde sensor with other compounds implies the presence of other compounds in the indoor air. In this case, the high molecular weight relative to indoor air of the detected VOCs reflects a shortfall in the performance of the ventilation system.

The supply and exhaust outlets of the ventilation system are located on the ceiling, while the monitoring device was placed at a height of no more than 40 cm. Thus, the data obtained in the study indicate that the air renewal was not being effective for a complete renewal of the entire volume, being limited to the upper stratum of the air in the rooms.

In this respect, manual ventilation with windows on an ad hoc basis was effective in sweeping the total air volume of the room, removing the higher molecular weight compounds.

Proper indoor air quality has a lot to do with adequate air renewal, with how we ventilate the spaces in which we live and work. And in this respect, the mechanical ventilation systems (preferably double flow and with heat recovery, for reasons of energy efficiency) are a great tool for guaranteeing the minimum required rate. However, like any other system, it is not exempt from requiring a specific design and adequate regulation.

Monitoring of energy-efficient housing

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