Rather than restricting our designs to fit a factory panelised system, we specialise in pre-cut timber frames. This allows us to design homes to any desired shape, even with curved walls, while always maintaining the air-tightness of our structures to to the Passivhaus standard. It also means we do not need a crane on site to erect the structure or send in many lorry-loads of panels, which provides a distinct advantage on sites with difficult access.
The Touchwood Homes build structure is created from superior 300mm thick I-beams rather than cheaper twin wall systems. We use I beams because they provide a much stronger overall structure, they are rigid through the entire wall, and they create ‘cells’ between each wall stud. These cells are then be filled with Warmcel insulation, allowing the Warmcel to be installed to very high densities. In our experience of using the traditional twin wall structure that the insulating material leaks out between the studwork and so does not become installed to such a high density.
Constructing from I beams, rather than solid timber, also results in minimal cold bridging through the walls because there is minimal solid material crossing the building’s thermal envelope, which when coupled with insulation and airtightness results in a frame that will meet the Passivhaus standard.
The entire structure is then then externally sheathed with an air tight, solid TG fibre board to provide a completely robust, long term air tight solution. We’ve found that this is much more robust than the traditional use of membranes and sticky tapes on the inside face of the wall, and avoids follow on trades being bogged down dealing with working around a membrane.
Cellulose fibre insulation is pumped into the walls and roof. With I beams walls much higher Warmcel densities can be achieved vs cheaper twin wall systems, resulting in a better thermally performing home.
We cover the entire external surface of the build with our TG board, mastic sealed at all joints to form a long term robust air tight layer. We do not use cheap tapes and membranes.
I beams have only the 9mm web passing through the structure, so minimal cold bridging occurs.
Another feature is that, rather than using “cheap” traditional trusses for our roofs, we use glulam ridge beams which primarily creates a simplistic airtight layer following the external side of the building, omitting the complexity of having the airtight layer duck inside the roof at eaves level.
Glulam ridge beams also allow the roof space to be completely open, giving the attractive option of dramatic vaulted ceilings.