I was recently called out to a property that has damp issues that nobody can seem to get to the bottom of. The reported history is damp proofing was previously carried out has gone wrong, and has been recently been carried out again. Mould and condensation issues have persisted even since the installation of the Nuaire Drimaster heat. There has been over 7 surveys on this property, and we were called in to get to the bottom of it. We were instructed to carry out gravimetric profiling of the walls following the methodology in BRE Digest 245, thermal imaging of the building fabric internally and externally looking for any hidden anomalies, a full ventilation survey of the building, and take air flow measurements using our calibrated anemometer.  Full data logging of the building was to be carried out, the client wanted this as they knew how limited a condensation survey can be at this time of the year, it’s no good turning up at 1pm to think your going to find condensation ………it will be long gone normally! Data logging of the internal environment may seem excessive and possibly expensive to some, but this chap has had many years of this, and to him it is money well spent to finally end all this misery of mould and rising dampness issues.

When I first walked up the stairs in the below picture is what I could see!!!

a dangerous piv install

To some people this may seem like nothing, some pictures on a wall, a smoke alarm and some kind of grill…….The grille is actually a diffuser (in red box 1) for the Nuaire Drimaster Positive Input Ventilation System, now here comes the dangerous bit, these things are supposed to be installed 1m away from a smoke alarm, unless there is a blanking plate to ensure no air from the loft will blow over it, as this will potentially stop the smoke alarm from going off. Now note in the other red box (2) there is a carbon monoxide alarm, well for obvious reasons there shouldn’t be fresh air blown over this either, otherwise it will not go off. So we now have 2 alarms that have been installed to protect the family that will not work and potentially putting them at risk.

The piv filters have also never been cleaned also.

There are a few reasons why this install didn’t  work, one of these was because there was no undercut beneath the doors, there was no roof ventilation, insulation was missing creating cold spots, the extraction fans were set up wrong, and obviously not commissioned, radiators were installed in the wrong place…….all of this should have been picked up by an averagely competent ventilation surveyor that has completed Bpec training on this subject. Positive input ventilation does work very well, and is something we use on a regular basis, however it is imperative it is installed correctly.

This is the reason we charge for surveys, we do this so we can afford to pay for our training and also give the client the best advice possible. This free survey and cheap piv installation could have cost them there life……and it didn’t even work.

If you want a survey and a professional installation contact Complete Preservation on 01225 769215



Posted by Complete Preservation


  1. 1. Do you supply and fit the Nuaire Drimaster Eco, or another type of positive input ventilation?
    2. If so how much?
    3. Can I get an insurance backed guarantee for the cure?
    4. I have had a quote and they have recommended a loft piv and three dmev fans, would you recommend this?

    The property is a small I bedroom bungalow.


    1. Hi Sasha.

      1. Yes we supply and install various Nuaire drimaster pivs, and other types.

      2. I couldn’t give you an exact price without a survey, there are many things to consider.

      3. You will not be able to get an Insurance backed guarantee for this type of issue, however a decent survey and install will solve the issue. We have extensive knowledge on these issues including full before and after atmospheric monitoring.

      4. There is no way you would need a piv and 3 dmev extraction fans. One piv or 2 x dmev fans would be more than enough.

      Hope this helps, any questions give me a ring on 01225 769215



  2. We had one of these fitted and all it does is blow cold air in from the loft. Quite an expensive experience as the pathetic 400w heater is useless. Just wasted £700 !


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