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    • #59736
      Adam Harper
      Participant

      Hello

      I just attended a webinar this evening about Retrofit hosted by a community energy group. There was a chap there billed as an ‘expert’ who operates in Yorkshire as a home retrofit consultant (won’t name any names) who claimed that ‘the only way to further insulate a filled cavity wall without causing condensation is to install internal wall insulation’.

      Its a little while since I’ve done dew point calcs, but would internally insulating a cavity wall not move the dew point from the cavity into the inner wall leaf, and therefore increase moisture risk?
      I’m sure I’ve read of EnerPhit projects with filled cavity walls that have had EWI installed with no issue, so I’m at a lost to why he’s saying you can’t installed EWI on a cavity wall. Would a appreciate a technical answer as I’d like to challenge this chap is he’s making incorrect statements.

      Thanks
      Adam

    • #59920
      Paul Jennings
      Participant

      Hi Adam,

      There have certainly been EnerPHit projects with external wall insulation on cavities, but there have also been projects where the removal of existing cavity wall insulation has been proposed to avoid the possibility of such problems.

      Unfortunately, I’m not yet skilled with WUFI, so can’t examine this at a technical level.  But I’m doing Joseph Little’s online course in November, maybe I can work this one through as part of that! Maybe someone else can help?

      But, maybe we should be naming names? There is far too much incompetence out there, right from the top of the new Green Deal downwards. Get your facts right, do your research, then skewer the guy! But then I am somewhat of an extremist!

      Have I shared my solution for the poor quality of newbuild from volume housebuilders? Conversation for adown the pub, whenever that becomes possible again.

      Good luck.

      Paul Jennings, Aldas

       

    • #59923
      Paul Jennings
      Participant

      Hi Adam,

      https://passivhausrefurb.blogspot.com/search/label/cavity%20walls

      I talked with another Adam, Adam Dadeby, who did the excellent EnerPHit refurbishment of Hunters Moon in Dartington.  The link is to his post about removing existing cavity fill (which had suffered from water penetration) and then replacing it with graphite beads before the external leaf was clad externally.  He reckons it took him up to 2 days to vacuum out the old insulation, which he did himself to save money.  Used an industrial vacuum cleaner and some extension pipe, had to work around wall ties, but was made feasible because all the existing windows had been removed.

      But clearly was insulating externally on a filled cavity wall. Don’t think he has done any moisture monitoring in the fabric, but no sign of any problems nearly 10 years on.

       

    • #60290
      Nick Owens
      Participant

      As part of my MSc at University of Kent, I recently modelled 200mm wood fibre EWI on a cellulose-filled brick an block cavity wall, with 0.5 inch wood siding externally externally.  I used DesignBuilder as the simulation tool, which incorporates the EnergyPlus v8.9 simulation engine.

      The condensation analysis given by DesignBuilder says “structure is free from condensation”  “number of condensation interfaces: zero” , and “Thermal quality good. Mould growth unlikely”.  And that’s without taking out the old cavity insulation.

      So it seems OK, and what’s more I’m going to build it as soon as I can get planning permission.

      • #60294
        Adam Harper
        Participant

        Hi Nick,

        Thanks that sounds interesting.  I see EnergyPlus is a US tool, do you know if it uses ISO standard conventions for the condensation calcs?

        Let us know how you get on with the install, which is presumably wood fibre retrofitted onto an existing cavity wall dwelling?

        Thanks

        Adam

    • #60293
      Adam Harper
      Participant

      Hi Paul

      I meant to reply to say thanks for the advice and suggested link to Hunters Moon. I heard this from a guy called Andy Walker of Sure Insulation. He advises households on retrofit and his company used to install IWI.

      Cheers

      Adam

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