On Site: Harpenden Passivhaus



Contract Value:

Circa £750k

We are building a replacement dwelling on the site of an old bungalow. The new-build will be an all-electric timber frame 4 bedroom Passivhaus Plus using the ‘homes as power stations’ concept. This means it generates much more electricity than it uses and it can operate ‘off-grid’ without need for grid electricity supply for much of the year, saving any excess in its battery system and further excess sold back to the grid. It affords the occupiers a warm and comfortable environment with constant fresh air. The designers bere:architects also designed our RIBA award-winning project Max Fordham House.

This property is also one of the first installs in the UK of a Pichler PKOM4 fully integrated 2 stage air source heat pump hot water cylinder with MVHR, heating and cooling through air, (air to air), heating through water (underfloor) and hot water as one item. It has been integrated into the Loxone smart home system. The property takes its water from a well and has a huge rainwater harvesting tank which supplies toilets and the washing machine. A 3 stage waste water recycling centre was installed to treat sewage. The resultant ‘grey-water’ is used to irrigate the garden and surrounding fields.

Light and heating sensors in the house communicate with the smart home system which automatically operates the external shutters on windows to regulate internal temperatures. Installing a sprinkler system in a timber frame house also brought complications and required integrated auto water shutoff with four water sensors around the house. If any of the bathrooms or utility room leak water, it auto shuts of water for whole house to prevent damage to the timber frame or insulation.

  • After 5 years of living here we are moving to the country and it breaks my heart to leave the beautiful house that you created for us.  I wanted to say thanks again for the beautiful work that you did on our building - it’s been amazing to live in and you guys did a first class job. Would always recommend you if someone asked for an excellent contractor.
    — Nick H
  • “Bow Tie Construction were very professional, they did things to a very high standard and paid a lot of attention to detail. When small issues were flagged here or there they were always keen to investigate and fix them.”
    — Francis M
  • “We’re expecting a dramatic reduction in costs. We now know how much energy we’ve used (in March) and we rarely have the heating on compared to this time last year in our old house.”
    — Toni M
  • Your guys did a very good job on the [window] installation, nice and precise and the assemblies fitted perfectly....Very good silicon application too, with a nice 5mm joint. So please do thank them on behalf of Cristina and myself. We are very pleased.
    — Stephen M
  • "We’re really lucky to have them Bow Tie Construction working on our project. Thanks for all your fantastic work so far."
    — Nick H

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