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IMPACT OF DESIGNING THE SAME BUILDING TO DIFFERENT ENERGY PERFORMANCE STANDARDS ON LIFE-CYCLE COSTS

Stanislavs Gendelis, Andris

Abstract

This paper analyses how designing the same single-family building to different energy performance standards affects its life-cycle costs. The study compares five design scenarios for one building, starting from the current national minimum energy performance requirement, moving through a typical nearly zero-energy building solution and an enhanced NZEB variant, and progressing towards a highly energy-efficient Passive House and a Passive House PLUS solution with on-site photovoltaic generation. Each scenario is evaluated using life-cycle cost assessment over a 50-year period, including pre-construction, construction, use, and end-of-life stages, with harmonized assumptions for inflation, discount rate, and energy price development. Measured data from the first Passive House PLUS building in the Baltics are used to calibrate and validate the calculation inputs for space heating demand, internal gains, indoor temperature, and PV yield, ensuring realistic boundary conditions for the most ambitious scenario. Particular attention is paid to the relationship between reduced space heating demand, the contribution of rooftop PV generation, and the resulting annual and monthly energy costs. In addition to the baseline calculation, a sensitivity analysis is performed for discount rate, inflation rate, energy price escalation, and PV system performance to assess the robustness of the economic outcomes. The analysis shows that higher upfront investments in building envelope performance and PV systems lead to substantially lower operating costs and clearly different payback times for the considered standards. Under the assumed temperate-cold climate conditions of Latvia, the present national regulatory framework, and the adopted cost and price development assumptions, the scenario corresponding to a Passive House PLUS level design represents the most cost-effective option among all investigated and realistically achievable variants, exhibiting the lowest cumulative life-cycle cost curve and the shortest payback time within this context. The results illustrate that combining very low energy demand with on-site renewable energy production is not only beneficial from an environmental perspective but also a robust strategy for minimizing long-term financial risks for building owners under similar climatic, regulatory, and economic boundary conditions.

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