In the construction industry, it is the material production phase and the use phase of buildings’ life cycles that represent the greatest environmental burden. The presented research focused on wood constructions during their use phase. The primary objective of the research was to determine the amount of CO2 produced during the operation of specific wood constructions in connection with the energy demand for their heating. A correlation analysis of selected parameters revealed a statistically significant correlation between heating medium type and energy demand for heating (p = −0.5773) and between heating medium type and amount of CO2 produced (p = 0.4796). A more detailed analysis showed that, in terms of the average energy demand for heating, the column constructions were the most efficient among the compared construction systems, regardless of the energy standard. Similar findings were obtained for annual CO2 production in connection with the average energy demand for heating. The only difference was that the panel and log constructions exhibited almost identical parameters, which came as a surprise to some extent. The column constructions turned out to be the most efficient again, regardless of their energy standard. The analysis that focused on the heating medium type revealed statistically significant differences among the heating medium types in energy demand for heating (p < 0.0001). The constructions that used electricity for heating were the most energy-efficient. When the individual characteristics of the different heating media in relation to CO2 production were taken into account, the constructions that were heated using biomass were the least polluting. The constructions heated using electricity and gas showed a significantly greater deviation.