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

Most of the school buildings in Italy are high energy-demanding buildings with no ad-hoc ventilation systems (i.e., naturally-ventilated buildings). Therefore, reducing the heat losses of schools represent the main aspect to be dealt with. Nonetheless, the indoor air quality of the building should be simultaneously considered. Indeed, to date, energy consumptions and air quality are considered as incompatible aspects especially in naturally-ventilated buildings. The aim of the present paper is to evaluate the effect of different ventilation and airing strategies on both indoor air quality and energy consumptions in high energy-demanding naturally-ventilated classrooms. To this purpose, an Italian test-classroom, characterized in terms of air permeability and thermophysical parameters of the envelope, was investigated by means of experimental analyses and simulations through CO2 mass balance equation during the heating season. The air quality was assessed in terms of indoor CO2 concentrations whereas the energy consumptions were evaluated through the asset rating approach. Results clearly report that not adequate indoor CO2 concentrations are measured in the classroom for free-running ventilation scenarios even in low densely populated conditions (2.2 m2 person−1), whereas scheduled airing procedures can reduce the indoor CO2 levels at the cost of higher energy need for ventilation. In particular, when airing periods leading to the air exchange rate required by standards are adopted, the CO2 concentration can decrease to values lower than 1000 ppm, but the ventilation losses increase up to 36% of the overall energy need for space heating of the classroom. On the contrary, when the same air exchange rate is applied through mechanical ventilation systems equipped with heat recovery units, the ventilation energy loss contribution decreases to 5% and the overall energy saving results higher than 30%. Such energy-saving was found even higher for occupancy scenarios characterized by more densely populated conditions of the classroom typically occurring in Italian classrooms.

https://www.mdpi.com/2075-5309/9/5/110/pdf

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

A contribution for the quantification of the influence of windows on the airtightness of Southern European buildings

Energy saving and Indoor Air Quality (IAQ) in buildings are strongly affected by air leakages. Several studies reveal that the energy loss owing to leaky windows can account for up to 40% of the total building energy demand. Furthermore, at the design stage, the possible infiltration of outdoor air through windows is not taken into account when determining the nominal outdoor airflow rate of the ventilation system. This practice may result in an oversizing of the ventilation system and consequent energy waste. Thus, the air-tightness class of a wall assembly should be assessed for each window component considering the type of material, the presence of the seal, the type of closure, the sealing and the maintenance condition. In this paper, the authors present the experimental results of air-tightness measurements carried out using the fan pressurization method in three residential buildings located in the Mediterranean region before and after a window retrofit. Two different window retrofits were investigated: the application of rubber seals on window frames and the substitution of existing windows with new certified high performance windows. The effectiveness of such retrofits was estimated also in terms of energy saving. Test results demonstrated a high variability of the building air tightness after window retrofits, despite the fact that air tight–certified windows were used.

Experimental Air-Tightness Analysis in Mediterranean Buildings after Windows Retrofit

Building air leakage analysis for individual apartments in North China

An Experimental Investigation on the Air Permeability of Passive Ventilation Grilles

In recent decades, interest in the eco-efficiency of building materials has led to numerous research projects focused on the replacement of raw materials with mineral and biomass wastes, and on the production of mortars with low-energy-consuming binders, such as gypsum. In this context, five different fractions (bark, wood, branchlets, leaves, and flowers) of Acacia dealbata—an invasive species—were evaluated as fillers for premixed gypsum mortars, at 5% and 10% (vol.) addition levels and fixed water content. Although these biomass fractions had different bulk densities (>50% of variation), all the mortars were workable, although presenting different consistencies. As expected, dry density decreased with biomass addition, but, while mortars with addition at 5% presented a slight shrinkage, a slight expansion occurred with those with 10% addition. Generally, the mechanical properties decreased with the biomass additions even if this was not always proportional to the added content. The wood fraction showed the most positive mechanical results but flexural and compressive strengths of all the tested mortars were found to be higher than the lower standard limit, justifying further studies.

/pdf/gypsum-mortars-with-acacia-dealbata-biomass-waste-additions-2hazcgs4.pdf

Gypsum Mortars with Acacia dealbata Biomass Waste Additions: Effect of Different Fractions and Contents

The passive contribution of indoor coatings to improve interior comfort is an eco-efficient challenge nowadays. Gypsum is one of the more eco-efficient binders available to produce plasters. Acacia dealbata is an invasive plant species in many countries, and the management of its wood waste for fires prevention is imperative. This study intends to evaluate the effect of using Acacia dealbata bark waste, directly after milling (raw) or with additional thermal treatment (1 h at 250 ⁰C), as an addition to an industrial gypsum-based plastering mortar to passively improve indoor comfort. To prevent the biological colonization, air lime is also added. Two clay-based plasters are used for comparison, as this type of plaster is known for being highly hygroscopic, together with a reference gypsum plaster. Results show that both the gypsum-bark mortars fulfill the standard requirements and do not show biological vulnerability. They doubled the moisture buffering of the reference gypsum plaster and got closer to the hygroscopic performance of the clay plasters. The very similar results between the two gypsum-bark mortars suggest that the thermal treatment of bark is not an eco-effective choice. So, the raw bark-added gypsum mortar is selected as a promising coating material to passively contribute for indoor comfort in an innovative, eco-efficient, way. 

Eco-efficient plastering mortars for improved indoor comfort − The influence of A. dealbata bark addition

Traditional air lime-earth mortars: The effect of earth replacing the binder and the aggregate on performance and durability

In Southern European countries, due to the specific climate, economy and culture, a permanent heating practice during winter is not widely adopted. This may have a significant effect on the performance of indoor coating materials, typically tested considering hygrothermal conditions in the range of 33–75% relative humidity (RH) and 20–25 °C, which are common in continuously heated buildings. In this study, the indoor climate of four bedrooms located in Lisbon, Portugal, was monitored under operational conditions. Based on the data monitored in the case studies, characteristic ranges of indoor hygrothermal conditions were defined and compared to those considered in standard test procedures. In addition, numerical simulations were adopted to compare the hygroscopic performance of four plasters under operational conditions observed on-site. Results show that the four rooms, intermittently heated or unheated, do not provide comfort conditions over 50% of the wintertime, with temperatures lower and RH higher than the ones recommended by the standards. The MBVs resulting from simulations (under operational conditions) are qualitatively in agreement with the MBVs obtained under standard testing conditions. Nonetheless, future studies are recommended to evaluate if standard tests are quantitatively representative of the hygroscopic performance of coating materials in the Southern European scenario.

/pdf/a-discussion-on-winter-indoor-hygrothermal-conditions-and-236ph07v.pdf

A Discussion on Winter Indoor Hygrothermal Conditions and Hygroscopic Behaviour of Plasters in Southern Europe

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