The parameters and conditions that govern the ventilation requirements in residential buildings under current regulations worldwide are not harmonized. The reduction in energy demand and the increase in the thermal comfort in dwellings are mainly conditioned by these parameters. This article reviews and compares the ventilation flow rates in residential buildings in various countries: the United States of America, Germany, France, the United Kingdom, and Spain. It also compares the requirements of these countries with the requirements of the Passivhaus construction standard, which is recommended by the European Union as an example of nearly zero-energy buildings (nZEB). Furthermore, a model for a dwelling is created using TRNSYS software. First, simulations have been performed with the flow rates, ventilation strategies and envelope transmittance required by the regulations of each country. The cooling and heating demands have been obtained for representative cities in different climate zones. With these results, the impact of ventilation parameters in the heating demand of the proposed Spanish dwelling is analyzed. Secondly, the same dwelling has been simulated with the thermal envelope transmittance values recommended by the Passivhaus standard. The ventilation strategies of each country have been maintained. The influence of the ventilation can be observed uninfluenced by other design parameters. It is found that with the current ventilation strategies, the heating and cooling demand values required by Passivhaus can be reached in only a few warm climates. In other cases, the ventilation strategies will need to change, and heat recovery ventilation will be required.

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The COVID-19 crisis has changed daily habits and the time that people spend at home. It is expected that this change may have environmental implications because of buildings’ heating energy demand. This paper studies the energy and environmental implications, from a Life Cycle Assessment (LCA) approach, due to these new daily habits in residential buildings at their current level of thermal insulation, and in different scenarios of thermal retrofit of their envelope. This study has a building-to-building approach by using Geographical Information Systems (GIS) for the residential housing stock in the case of Barcelona, Spain. The results show that a change in daily habits derived from the pandemic can increase the heating energy consumption and carbon dioxide emission in residential buildings by 182%. Retrofitting all buildings of Barcelona, according to conventional energy renovation instead of nearly Zero Energy Buildings (nZEB), will produce between 2.25 × 107 and 2.57 × 107 tons of carbon dioxide. Retrofitting the building stock using energy recovery is the option with better energy and emission savings, but also is the option with higher payback time for buildings built until 2007. The methodology presented can be applied in any city with sufficient cadastral data, and is considered optimal in the European context, as it goes for calculating the heating energy consumption.

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District heating and cooling systems are designed and optimized to respond to the latest challenges of reducing energy demands while fulfilling comfort standards. Thermal energy storage (TES) with phase change materials can be employed to reduce the energy demands of buildings. This study considers a residential district located in Spain, where a general framework has been established to identify optimal combinations of energy conversion, delivery technologies, and operating rules. The Life Cycle Assessment (LCA) methodology was implemented within a mathematical model, and the objective function considered the minimization of environmental loads. Two environmental impact assessment methods were applied within the LCA methodology: IPCC 2013 GWP 100y and ReCiPe. Four optimal configurations were considered: a reference system (gas boiler and split-type air conditioners) and then three TES-based systems: one sensible (STES, water) and two latent (LTES1-paraffin emulsion and LTES2-sodium acetate trihydrate). Hourly environmental loads associated with electricity imports from the national grid were available. The conventional energy system always presented the worst performance from an environmental viewpoint, being penalized by the high consumption of natural gas. Regarding carbon emissions, LTES1 showed the lowest emissions, followed by STES and LTES2. Reductions in energy demands compensated the impact of paraffin, and results of STES are strongly dependent on tank design. However, considering the ReCiPe method, STES presented the lowest loads, followed by LTES1 and LTES2. Overall impacts of LTES1 with paraffin are higher than STES with water, mainly due to the paraffin and the high volume required.

Mechanical ventilation systems are essential for ensuring the indoor quality of air in nZEB (nearly Zero Energy Buildings) with a high level of airtightness. In cold countries, it has already been demonstrated that Heat Recovery Ventilators (HRV) recovering the sensible energy from air ventilation are needed to achieve the energy demand goals for nZEB set by Passivhaus. In tropical areas with hot temperatures and high relative humidity in the ambient air, the necessity of recovering latent and sensible energy with Energy Recovery Ventilators (ERV) has also been demonstrated. However, in warm climates with medium relative humidity levels, for example in cities located on the Mediterranean coast, the evaluation of the effectiveness of an EVR for residential buildings has to be analyzed and optimized. This article establishes the effectiveness of several control strategies for ventilation air systems including ERV with the aim of optimizing the air conditioning energy demand of dwellings located in several cities in the South of Europe. Possible control strategies have been analyzed to minimize the undesirable operation of ERVs which could otherwise increase the air conditioning energy demand for winter and summer seasons. The impact of the latent effectiveness and the effect of free-cooling on the air conditioning energy demand is also studied.