Why did Subarctic peoples use semisubterranean houses during winter?

In the context of the Subarctic culture area, Indigenous peoples utilized semisubterranean houses during the winter primarily to withstand the region's extreme weather conditions.1

These structures were designed to provide a "snug" environment against the harsh climate of the boreal forest (taiga) ecosystem. By excavating the houses into the soil and roofing them with beams, poles, and mats, these groups created insulated dwellings that offered protection from the cold that portable shelters could not provide. While some groups, such as the Deg Xinag, specifically utilized these excavated winter homes, other peoples in the region employed different durable structures, such as conical lodges covered with boughs, earth, and snow, to achieve similar thermal protection during the winter months.12