In this project the floor is supported by posts that are placed on a rectangular grid. Each grid cell measure 3x3 meters and represents a footprint for a modular floor and ceiling element that is strung between its 4 corresponding posts.

The floor and ceiling are part of the thermal envelope. They are both load bearing albeit the ceiling just supports the insulation, ducts, and cable trays.

This page focusses on a traditional timber frame floor and subsequently explores an potential alternative that provides a better thermal resistance.  

A floor element is an abstract notion that represents the assembly of various components, in this case 4 edge beams, the 4 joists that span the interior space between the edge beams, insulation, a bottom plate, and a subfloor. The entire assembly is shown on the left. 

In traditional wood construction floor joists are placed between the main supporting beams. On top of the joists is the subfloor, usually OSB or plywood panels. Hence the supporting beams and floor joists form a rigid structure that is meant to carry the weight that rests on the subfloor. 

This weight is described as either a dead or live load. The former is calculated as the weight of the building divided by total square meters in floorspace. The live load refers to the total load carried by the floor, including furnishings, occupants, and other objects that sits in the interior of the building.

A floor element can contain 3 layers of staggered insulation (pink, green, blue) which are stuffed between the joists.

However the insulation does not cover the joists and hence the latter forms a thermal bridge between the exterior and the interior which makes the thermal envelope of the building less efficient. 

Also, the insulation should be snug to the joist in order to prevent leakage through any gap between the joist and the insulation. Any such gap will breach the thermal envelope and forms another thermal bridge between the exterior and interior of the building.   

By cross hatching the floor joists into a lattice structure one could potentially reduce the thermal bridging (i.e. increasing the thermal resistance) while maintaining  the required load bearing capacity of the floor element.

Rather than using a solid timber joist one could imagine cutting the joists along its length in 3 sections and turn the bottom and top section 90 degrees. The resulting lattice will still form a thermal bridge but only on the cross sections of the lattice which is better than the thermal bridge of solid timber joists. One could even improve this lattice approach by offsetting the top section of the lattice so that it does not align with the bottom section anymore. 

Another advantage of this lattice approach is that the insulation can be stacked cross ways on top of each other (see image on left) and thereby one layer of insulation can cover any potential gap of the layer underneath or vv. This should improve the thermal bridging of the joist/insulation surface considerably. 

Slicing a solid joist in 3 sections and cross hatching them into a lattice structure will affect its load bearing capacity. 

However this could be improved by replacing each solid section with a truss type of structure, albeit with minimal height and hence a considerable number of web elements (See image on the left that shows a sideview of the 3 trusses combined). 

This combined with the staggered and cross layered layout of the trusses may provide an even load distribution/transfer to all(!) edge beams rather than to just 2 edge beams.  

In this example the width of the floor element is 300 cm while the height of the edge beam is just over 30 cm. Hence each truss is 10 cm in height i.e. each web element will be 2-3 cm high. 

NB A structural Analysis may be needed to make sure that the load bearing capacity of this assembly is sufficient and fit for purpose! 

The image on the left shows the ceiling profile i.e. ceiling joists, OSB, membrane, thick layer of insulation.