A comparative assessment of ventilative and mechanical cooling for residential zero energy buildings considering the future climate
CHALLENGE - With the increased global concerns on climate change, housing developers are under an obligation to move towards energy-efficient buildings. In the Netherlands, this resulted in a trend towards highly insulated dwellings which are more prone to overheating and therefore increased adverse health effects. Given the prospect of increased overheating risks in the future, it is important to assess the performance of ventilation and mechanical cooling to avoid overheating risks. Therefore, the following research question has been drawn up: “Is mechanical cooling the ultimate cooling strategy for residential zero energy buildings to avoid overheating risks in the future?”
SOLUTION - In this thesis, a comparative assessment is performed of ventilation and mechanical cooling using building performance simulations. The proposed methodology is generic which means that it can be applied to various residential buildings. The methodology has been applied to a case study building representing an existing detached house that needs to be renovated into a zero energy building. A design space has been formed varying in different building parameters such as insulation level, energy generation system and cooling strategy. The performance of these design variants is assessed in the field of thermal comfort, energy, and cost, for different scenarios that include the climate, household size, and the occupant behavior. For this study, the brute-force approach is used, making all the different combinations of all predefined design variables. Therefore, the total computational time had to be taken into account while defining the different design variants and scenarios, done using an external optimization program modeFRONTIER. This program includes different optimization algorithms and can change the source code of the TRNSYS model so that new design variants and scenarios can be automatically introduced into the simulation model.
BENEFITS - Mechanical cooling prevents overheating risks at negligible investment cost, but comes with an increased electricity consumption of 3 - 15%, and therefore increased operating cost, depending on the design variant, climate and occupant scenario. Through the use of photovoltaic panels, up to 64% of the electricity consumption for mechanical cooling can be directly fulfilled by on-site generated electricity.