A pre-assembled floor and ceiling panel for use in a building, the panel comprising: a plurality of joists , wherein each joist of the plurality of joists is formed of two C-shaped members attached back-to-back, and wherein the plurality of joists define a plurality of joist cavities between adjacent joists; a corrugated form deck disposed above and attached to the plurality of joists; a ceiling substrate disposed below and attached to the plurality of joists; an in-floor radiant heat member disposed between the corrugated form deck and the ceiling substrate; thermal insulation disposed between the corrugated form deck and the ceiling substrate; a floor material; and a layer of material disposed below the corrugated form deck, wherein the layer of material covers one or more flutes of the corrugated form deck to restrict migration of the thermal insulation into the one or more flutes, and wherein the layer of material is thermally conductive and the in-floor radiant heat member is attached to the layer of material such that the layer of material provides uniform radiant heat transfer from the in-floor radiant heat member through the corrugated form deck and into the floor material which is disposed above the corrugated form deck, wherein the layer of material comprises a plurality of holders for the in-floor radiant heat member, wherein the holders at least partially define the layer of material sized to fit within a joist cavity of the plurality of joist cavities, and wherein the layer of material has length and width dimensions similar to each respective joist cavity so as to conceal all flutes of the corrugated form deck between the adjacent joists. a plurality of joists , wherein each joist of the plurality of joists is formed of two C-shaped members attached back-to-back, and wherein the plurality of joists define a plurality of joist cavities between adjacent joists; a corrugated form deck disposed above and attached to the plurality of joists; a ceiling substrate disposed below and attached to the plurality of joists; an in-floor radiant heat member disposed between the corrugated form deck and the ceiling substrate; thermal insulation disposed between the corrugated form deck and the ceiling substrate; a floor material; and a layer of material disposed below the corrugated form deck, wherein the layer of material covers one or more flutes of the corrugated form deck to restrict migration of the thermal insulation into the one or more flutes, and wherein the layer of material is thermally conductive and the in-floor radiant heat member is attached to the layer of material such that the layer of material provides uniform radiant heat transfer from the in-floor radiant heat member through the corrugated form deck and into the floor material which is disposed above the corrugated form deck, wherein the layer of material comprises a plurality of holders for the in-floor radiant heat member, wherein the holders at least partially define the layer of material sized to fit within a joist cavity of the plurality of joist cavities, and wherein the layer of material has length and width dimensions similar to each respective joist cavity so as to conceal all flutes of the corrugated form deck between the adjacent joists. <EOS>