PROBLEM TO BE SOLVED: To provide a double-layer film forming tube duct used as a frame post that forms an air layer of the same shape and film thickness even if installed in any facility by using conventional equipment as it is, and to provide an agricultural cultivation facility where the tube duct is expanded and contracted to repeat the formation and disappearance of the frame post at any time.SOLUTION: Locking films 2 of suitable length are provided at both ends of a frame forming tube duct 1, and the frame forming tube duct is shaped to narrow both end folding width and to widen the center part to thereby reduce a load in a fixed position by the swelling pressure of a tube and to provide a measure to treat dew condensate falling down from an outside house. A nonwoven fabric 3 is provided to prevent the stagnation of the dew condensate staying in the frame forming tube duct 1, and the covering position of the frame forming tube duct 1 is determined to form a stable air layer of the same thickness and height even if installed in any place, thereby maintaining heat insulating performance and attaining a scenic view.【課題】慣行設備をそのまま使用して、どのような施設に設置しても同形同膜厚の空気層を形成する骨支柱となる二重膜形成チューブダクトとそのチューブダクトを膨縮して随時骨支柱形成消滅を繰り返す農業栽培施設を提供する。【解決手段】骨形成チューブダクト１の両端に適当な長さの係止フイルム２を設けることと両端折幅を狭め中央部を広くする形状にすることで、チューブの膨らみ圧による固定位置での負荷軽減と外張りハウスから落下する結露水処理対策とし、不織布３を設けることで骨形成チューブダクト１内に溜まる結露水の溜まりを未然に防ぎ、骨形成チューブダクト１の被覆位置決め確定をすることでいかなる設置場面に設置しても安定した同厚高の空気層を形成し保温性能維持と景観を図る。【選択図】図４
