The effect of the ventilation retrofit in a school on CO2, airborne particles, and energy consumptions

Abstract

The energy retrofit of existing buildings is a key strategy to reduce the energy costs of the building sector. Amongst the retrofit solutions, the adoption of mechanical ventilation systems represents a necessary approach for buildings with high crowding index, such as schools. The air quality in schools is a main issue since children spend a significant fraction of the year in such microenvironments. To date, the scientific literature has carried out several studies concerning the air quality in naturally ventilated schools worldwide, nonetheless most of the studies performed a general evaluation of the air quality just using the CO 2 as a comprehensive indicator. This is an oversimplified approach since the indoor air quality is affected by several pollutants, including airborne particles, whose behavior cannot be predicted by the CO 2 one. The aim of the research is the evaluation of the effect of the ventilation retrofit in a classroom on different indoor air quality parameters and energy consumption. To this end a mechanical ventilation system with a heat recovery unit was installed in a test-classroom and tests with CO 2 -based demand controlled ventilation were performed. CO 2 levels and indoor-to-outdoor particle concentrations were measured and compared to the pre-retrofit ventilation conditions (i.e. manual airing procedures). Results showed that mechanical ventilation systems have simultaneous positive effects on the different pollutants investigated as well as on ventilation heat losses: indeed, lower indoor-to-outdoor concentration ratios, with respect to the airing approach, were detected simultaneously for CO 2 , sub-micron particles and PM 10 .

Indoor Air Quality: A Focus on the European Legislation and State-of-the-Art Research in Italy

“…Such topics are important because, based on the subpopulation interested, such as suggested by Manigrasso et al [50], which estimated the particle regional respiratory doses for both combustion and non-combustion aerosol sources currently encountered in microenvironments, with special regards to the age of subjects. Recent papers on school environments are related to monitoring PM, NO x , VOCs, and CO 2, with regard to the ventilation efficiency and the energy consumption [51][52][53][54][55][56]. As to the radon exposure, according to two papers, the schools are vulnerable targets due to the long daily childhood presence, and the radon risk could be reduced by low-cost interventions (e.g., implementation of natural air ventilation and school maintenance) [57,58].…”

The Effect of Ventilation Strategies on Indoor Air Quality and Energy Consumptions in Classrooms

“…Therefore, as expected, the only solution to improve simultaneously the energy consumption and the indoor air quality is a ventilation retrofit by installing a mechanical ventilation system equipped with a heat recovery unit. Indeed, the hypothesized constant air volume ventilation system with a heat recovery efficiency of 90% (MV EN 1) [13], could guarantee a reduction of the ventilation heat losses down to 2.25 × 10 3 MJ (7% of the total energy need for space heating). Such Q H,ve value is still higher than that typical of natural ventilation, but such scenarios are not comparable since they lead to extremely different indoor air quality.…”

“…Nonetheless, the introduction of the new regulation on the performance of buildings [3], i.e., the introduction of nearly zero energy buildings (NZEBs) as the new building target [4,5], will force the building sector to handle simultaneously the heat losses and the air quality issues, since ventilation approaches not properly designed will likely not fulfill the limitation on energy need for space heating typical of the NZEBs [6][7][8]. Apart from new constructions, the strategic challenge in view of the reduction of the energy consumption of the building sector is the energy retrofit of the existing buildings [9][10][11][12][13]. This is even more important in countries (like Italy) characterized by a huge percentage (roughly 70%) of buildings built before any regulatory indication on building energy efficiency [14][15][16] and then without any carefulness to the ventilation issues.…”

Indoor Air Quality Assessment: Comparison of Ventilation Scenarios for Retrofitting Classrooms in a Hot Climate

“…As established by Stabile et al [16], energetically retrofitting existing buildings is key for reducing energy costs in the building sector. For this reason, retrofit strategies in the existing educational stock in Europe have fostered the implementation of consumption-saving solutions, mainly considering thermal and energy-based approaches [5].…”

“…For this reason, mechanical ventilation and heat recovery systems are widely incorporated to achieve adequate IAQ in existing school buildings [40] and a necessary approach for buildings with a high crowding index [16]. Schibuola et al [6] analyzed a demand-controlled ventilation system to retrofit a university library in Venice, reaching total primary energy consumption savings of up to 33% for a ground-source heat pump.…”