Touchwood Homes

Our Build Method

Touchwood Homes's structural solutions to creating passivhaus homes

We build the framework of our homes from ”I beams”, so called because of their I shaped structure, which create a very strong core to the wall, with the capacity to contain an ultra thick, super-high density volume of insulation material, for which we use WarmcelOur I beam frames also compartmentalise the wall studs into distinct bays which allows the insulation material to be installed at higher density.

ibeams

The beams themselves are made from wood grown on sustainable forest plantations. The wood is cut to plan on CNC machinery which allows each part of the structure to be precision cut for each individual section of the building. This enables us to create buildings of virtually any physical shape, and put each piece together as labelled for speed and efficiency on-site.

Once our frame work is complete, we add further strength to our building by means of an external sheathing system, an air-tight and robust solid TG board, which covers the entire structure. This is far more efficient than the more traditional use of sticky tapes and membrane for the air-tight layer! Another big advantage of our external sheathing system is that the ‘follow-on trades’, electricians and plumbers, have no need to cut into it to carry out their installations, so their workload is simplified and allows them to finish and be off site more quickly than they might be with more traditionally built homes.

This solid build structure is impenetrable to wind and rain and ensures a draft free home that requires very little heating. Even in the harshest weather, wind cannot blow through the dense insulation of our homes, making them far more comfortable and needing less energy to keep warm.  To obtain Passivhaus certification homes are tested for air-tightness and the maximum level must not exceed 0.6 ach. The typical air-tightness values  our build system achieves is 0.2 ach, which is considerably more efficient than required.

We usually build our walls and rafters from 300mm I beams, which provides a U value of 0.13, which is sufficient to achieve passivhaus certification for a design with a good form factor, however our system is flexible and if you require higher U values, we can also use 350, 400, or even 450 beam, for which our U values are 0.11, 0.10, and 0.09 respectively.  

Foundation diagram

Insulation diagram

Eaves diagram

...and so in implementing these we have:

Effective insulation

Cellulose fibre insulation is pumped into the walls. Our substantial I beams structures are the only successful way to achieve necessary density of insulation material. Cheaper twin wall systems are difficult to install with cellulose fibre to the required density. You can learn more about the Warmcel insulation we use here, or view their promotional video on Youtube

 

Prevention of draughts

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.

Combated the issue of 'cold-bridging'

I beams have only the 9mm web passing through the structure, so minimal cold-bridging occurs.

Our earliest Passivhaus achievements

Howe Park

Fox Barn

Porters

Our non-panalised build system has huge advantages over conventional builds, due to the fact that when the frame is completed your follow-on trades can get get straight to work on installation of their first fix wiring and plumbing, directly within our I beam walls and ceilings, thus avoiding the time consuming and costly phase of creating a service void around all interior walls. It also avoids first fix works becoming mixed up with an internal airtight layer. The electrician on our Hennerwood project commented that his works took just 3 weeks to complete, instead of 8 weeks on another newbuild project comprising of an internal air-tight barrier where he had to constantly reseal with tape any penetrations to the layer.

Our system also allows us to build to any design, there is not the limitation of trying to constrain a design into transportable panels, giving us freedom to do curved walls, crown roofs and any other feature your design may have.

  • I was new to the concept of Passivhaus houses but after much research I decided that it made sense or our new home to be built to this high standard of energy efficiency. We chose Touchwood homes, who  explained to us that their robust rigid external air-tight layer system, unlike  traditional sticky tape membrane systems, would not only guaranteee a passivhause degree of air-tighness but would also, for the slight increase in initial costing, save me a fortune on the cost of follow-on trades who would have otherwise have to work around flimsy internal membranes. As a result I have seen for myself how quickly and efficiently the plumbers and electritians have been able to complete their work and how much time and money this has saved me already!

    Paul

    Hennerwood Passivhaus
  • We have been astonished by the performance of the house…with cellulose fibre insulation Installed to test densities of 70 and above. Our son who is a commercial building energy assessor used his thermal imaging camera to check the installation and was unable to find even the smallest area which was not filled over the entire house.

    Colin

    Higher Pytte Cottage, Devon
  • I am glad that they [Grand Designs] covered your timber frame so well, such a beautiful example of what can be done with wood – I am so pleased that we chose you for the job and I am more than happy to recommend your services.

    Peter

    "Roundhouse", Milton Keynes
  • We have now been living in our house for 5 months and it is a revelation – why are all houses not built to this standard?! What’s most surprising is the ‘stillness’ of the house, no drafts, exceptionally quiet and clean controlled air distribution, makes for a very relaxing place to be. Passivehaus is the future of building and the Touchwood team did an excellent job with our beautiful new home

    Ben

    Weyhill, Hampshire

To complement the air-tight well insulated structure of your home, it is vital that the building’s foundations are laid to minimalise thermal bridging from the grounds surface and so compromise the overall efficiency of the home.

The build efficiency of our homes ensures that  cold air and dampness cannot permeate the walls, roof or foundation, but if the windows and doors are substandard, then your home will not perform so well. 

The advantages of living in a Touchwood Homes ‘air-tight’  home

  • No conventional central heating system needed, saving substantial construction costs, and of course running costs.
  • Minimal heating demand so very low heating bills – it is common for the MVHR system to supply all required heating via 2kW heater
  • Stable internal air temperature from heavy weight insulation (typically 6-8 tonnes of insulation / house).
  • Foundation slab inside the thermal envelope so is all used as thermal mass
  • Excellent air quality from MVHR unit supplying house with constant filtered fresh air
  • No cold draughts inside the home due to air-tight construction
  • Very quiet, calm internal space from super dense Cellulose insulation and triple glazed windows