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One possible solution that mitigates the effects of climate change is the implementation of vertical greenery systems, which have the potential to reduce the need for cooling and provide energy savings for heating. This paper evaluates the effects of an innovative modular green wall on indoor temperature and energy use in a residential case study building. This research was carried out on a residential house in the city of Ghent, Belgium, whose southwest facade is covered with a specific type of modular green wall (a structure with a specific substrate and plants that have the ability to purify water so that it can be reused in the house). The monitoring process included four different temperatures (in front of and behind the green wall, in the substrate, and on the wall without greenery) during winter and summer periods. To analyze the effect on the internal temperature and energy use, a DesignBuilder simulation model was built and validated against these experimental results. This green wall has proven to have the greatest effect during the hottest summer days by reducing the indoor temperature by up to 3.5 °C. It also effectively increases the indoor temperature by up to 1.4 °C on a cold winter day, leading to energy savings of 6% on an annual basis.

A mathematical model that governs unsteady coupled moisture and heat energy transport through an exterior wall covered with vegetation is described. The unknown temperature and moisture content of the plants and canopy air are represented by a system of nonlinear ordinary differential equations (ODEs). The transport of moisture and heat through the support structure, which includes insulation and soil layers, is defined in a series of nonlinear partial differential equations (PDEs). After setting out the model, this article presents and discusses a set of numerical applications. First, a simplified system consisting of a brick wall covered with climbing vegetation is used to study the role of individual variables (e.g., wind speed, minimum stomatal internal leaf resistance, leaf area index, and short-wave extinction coefficient) on the hygrothermal behaviour of the green wall. Thereafter, more complex green wall systems comprising a bare concrete wall, mortar, cork-based insulation (ICB), soil and vegetation are used to evaluate the influence of the thermal insulation and substrate layers on the heat flux distribution over time at the interior surface of the wall, and on the evolution of the relative humidity, water content, and temperature throughout the cross section of the green wall. The numerical experiments proved that vegetation can effectively reduce exterior facade surface temperatures, heat flux through the building envelope and daily temperature fluctuations.

Vertical greenery systems (VGS) are effective at solving urban heat. They can absorb noise pollution and dust, and, aesthetically, they are positively perceived. Systems using hydroponic irrigation and nutrition, in combination with mineral wool as a base, are light and effective (they are able to hold water, with a high percentage of air, and a good mechanical structure to hold the plant stable). However, the functionality of a system can be compromised if the water supply is depleted or the irrigation system fails. This deficiency can be partially remedied if a certain amount of biochar or a suitable organic fertilizer is also a part of the system. The research task consisted of verifying this assumption and determining the effective amount of the biochar. Samples with different amounts of biochar were examined under the same temperature and humidity conditions; extended drying times, additional costs, and safety tank size savings were found. Subsequently, the effective amount of the biochar was determined by the Data Envelopment Analysis (DEA) method. It has been experimentally verified that biochar has a positive effect and prolongs the drying time; the additional costs are almost offset by the benefits. It should be noted that the results are valid for central Europe, and may be modified for different climate and economic zones.