Bio-sourced materials and indoor pollutant emissions: second measurement campaign of the EmiBio project

The indoor air of our buildings contains pollutants

The indoor air of any kind of building contains pollutants in varying concentrations originating from different sources such as the materials used, furniture, activities in the building such as cleaning. Even human activities outside the building can add pollutants to indoor air.

When combined with poor ventilation / airing, these sources engender indoor air pollutant concentrations that can be very high. The EmiBio project focuses on any specific emissions from bio-sourced materials, cellulose wadding and wood wool.

For this purpose, when Ademe (French environment and energy saving agency) issued the call for projects, Cerema decided to partner with “Institut Mines-Télécom de Lille-Douai”, “Institut Mines-Télécom Atlantique”, “Université de Picardie” and “Université d’Artois”, in order to set up the EmiBio project. 

Objective of the EmiBio project and relevant pollutants

The objective of the EmiBio project is to assess the emissions of Volatile Organic Compounds (VOC) from certain bio-sourced materials, whether the VOCs originate from additives contained in the bio-sourced materials, from secondary chemical reactions or especially from development of micro-organisms (mVOC).

Moulds are more likely to develop on natural materials containing carbon at certain levels of heat and humidity. These moulds themselves emit specific pollutants which could possibly then be found in the indoor air. This is what the EmiBio project is seeking to verify.

N.B.: Volatile Organic Compounds (VOC) comprise a huge number of chemical substances that can be natural or artificial in origin. Within housing, workplaces and public areas, non negligible concentrations may exist due to the use of certain paints, cleaning products, and materials used for construction of buildings and furniture. They may cause a deterioration in indoor air quality, with potential impact on the health of occupants in the medium or long term.

A 6 phase project

The project is divided into 6 separate tasks, 3 of which are purely technical.

The first technical task concerns the assessment of VOC and mVOC emissions on the scale of the material in the laboratory. This task began right at the start of the project in October 2018 and should end in December 2021. It is being performed in parallel with the subsequent tasks, because it uses the results of tests performed on the materials used on the real site, or set up in experimental units (see next tasks).

The following task, which we are concerned with here, concerns the monitoring of VOC and mVOC emissions and hygro-thermal transfers from 2 real buildings, where the external walls have been insulated using bio-sourced materials, i.e. wood wool and/or cellulose wadding.

The first tested site has a brick structure and is insulated with wood wool from the interior, which is held in place by wooden uprights. Here is a simplified diagram produced by one of the partners, Université d’Artois:

The main difficulty in this task consists in selecting the test sites and their availability. The measurements can be intrusive (measurements of hygro-thermal transfers through solid materials), but above all they mean that the room being tested cannot be used for 2 periods of 15 days; once in the summer and again in the winter.

A series of measurements of pollutants in air, emissions from walls, of hygro-thermal conditions in the room and of the presence of moulds is carried out during these two campaigns.

In addition, an indoor air quality/ventilation diagnostic is carried out on the entire building in order to complete the interpretation.

Finally, the last technical task consists in monitoring the hygro-thermal transfers and emissions from multi-layer walls re-constituted and placed in an experimental unit. This task is in parallel to the above task. Its aim is to test walls identical to the walls on the real sites, but in controlled hygro-thermal conditions.

These different tasks should enable the project team to: (i) draw conclusions about a possible emissions signature of the tested bio-sourced materials; and (ii) if this signature exists, to verify after implementation whether this signature remains blocked within the material in the wall, or if it is to be found in the indoor air on the test sites.

Finally, the last technical task consists in monitoring the hygro-thermal transfers and emissions from multi-layer walls re-constituted and placed in an experimental unit. This task is in parallel to the above task. Its aim is to test walls identical to the walls on the real sites, but in controlled hygro-thermal conditions.

These different tasks should enable the project team to: (i) draw conclusions about a possible emissions signature of the tested bio-sourced materials; and (ii) if this signature exists, to verify after implementation whether this signature remains blocked within the material in the wall, or if it is to be found in the indoor air on the test sites.

The first measurement campaigns have been carried out on the first selected site

It was because of the type of insulation material used that Cerema asked the first municipality in the suburbs of Lille to participate (Nord department). The first two measurement campaigns were therefore carried out on the town hall building that was renovated and extended in 2013.

This building was insulated from the inside using wood wool, applied to the walls. In addition, the building was awarded the HQE label (high environment quality). The chosen room is the town hall’s wedding hall.

The first measurement campaign took place in July 2019 to be representative of the summer period. The second measurement campaign, in the winter period, took place in late January and early February 2020. This campaign involved three partners:

• “IMT Lille-Douai” for measurements of emissions on wall surfaces, “IMT Atlantique” for sampling by impaction of air-borne micro-organisms which are then placed for culturing in the laboratory,

• Université d’Artois for hygro-thermal monitoring – temperature and humidity (extended for 12 months),

• and Cerema, for measurements of indoor air pollutants and the building diagnostic.

Focus on measurements performed in the indoor air

In order to illustrate the extent of the measurements carried out on site, here we focus on the sampling carried out for the indoor air pollutants activity by Cerema:

• Screening of the pollutants present is carried out at regular intervals in the room by a portable chromatograph. This represents more than 170 samples per campaign, to be analysed and compared!

• In addition, active tubes are placed for 24 hours in order to sample air pollutants and help to identify them. These tubes are then analysed in the laboratory and this analysis is in addition to the analysis performed on site. For this stage, Cerema and “IMT Lille-Douai” placed different tubes, so as to have an analysis that would be as comprehensive as possible.

• Then samples are taken of a typical indoor air pollutant family, aldehydes, using passive tubes specific to these pollutants. These tubes accumulate these pollutants for one week (x 2 weeks), and are then analysed in the laboratory.

• Finally, additional devices are used to measure conventional indoor comfort indicators, i.e. temperature, relative humidity and CO₂ concentrations, a very good indicator of confinement in a room. In addition, these devices measure the total light VOCs and the total VOCs present in the room.

Preliminary results based on Cerema’s data

On this first site, pending the complete analysis of results from all the partners and cross-referenced analysis of these results, the first indications nevertheless are emerging from Cerema’s data concerning air in the room:

• The level of air pollutants in the room on site no.1 is higher in the summer than in winter, despite abundant airing of the room (overheating);

• The total level of pollutants remains low overall, but is not negligible;

• To date, pollutants judged initially as being possibly typical of micro-organisms have not been found in the indoor air. These findings remain to be deepened (based on other pollutants, cross-referenced with data from the walls).

Of course these results remain to be confirmed in the subsequent stages of the research.

The winter campaign measurements have recently been collected by the three partners and will be exploited in parallel with measurements from the first summer campaign carried out on the same site. The conclusions therefore remain to be drawn.