Chehalis is a PREMIUM model built with the thickest wall of 70mm (2 3/4) and has a single wall thermal mass rating of R-12. The windows and doors are premium grade with double glazing, fully weatherstripped and multi locking hardware. The kit is ready to mount on a concrete slab or wood floor. The tall front windows provide plenty of light for an interior with a vaulted ceiling and this model can be customized as required, make it larger, add windows and doors, or create your own design. Insulate the roof and floor and this becomes a comfortable extended living space with just a wall mounted HVAC heating/cooling system, ideal for an office, sewing or games room.