UPDATE:  As of late 2016, Nuaire have released a new updated range of DriMasters – called DriMaster Ecos.  These are blue, not green.  See right, and also see HERE

TheSAM_1818[1] main purpose of this site is to give you my views and experience of a Nuaire Drimaster heat PIV anti condensation system installed into my “new” home – a 1930’s detached old house.  We had condensation issues – see HERE for details, but in summary:

  • Bedroom windows were “wet” every morning, needed wiping/drying daily (even with windows slightly open)
  • Mould growing in corners & ceiling edges, clearly painted over by old owners
  • Water “running down” walls in bathroom after a shower etc

So clearly, we loved the house and needed to deal with it.   See HERE for details of other tips we applied, but then we installed this PIV system.

Anyhow, we all know mould/damp is a pain, and we thought we’d be proactive about it, and thus try and avoid any future problems (like mould behind wardrobes etc) – especially as we’ve just started decorating the new house.

A couple of “internet friends” on a forum mentioned http://www.envirovent.com/ and that they had a PIV system installed from them, and had astounding results.  Environvent seem to be a consultancy/installer and not really suitable for DIYers – and hence the cost is fairly high.  But, the first-hand results I heard were positive.  So I started looking for alternative PIV systems…

What is a PIV system?

Well, its a “Positive Input Ventilation” system which basically is a system which increases air pressure inside a house which forces older/wetter air out of the house and thus prevents condensation.  Thats the theory, and to be fair I’m not entirely convinced it isn’t a snake-oil product!  The forum threads http://markbrinkley.blogspot.co.uk/2005/09/shit-misses-fan.html and http://www.diynot.com/forums/viewtopic.php?t=110195&start=0 give both sides of the story – many people saying the systems are superb, and a few saying they are not.  Interestingly, the miracle stories seem to be from owners, and the negative comments seem to be from the theorists.

I came across Nuaire Drimaster products http://www.nuaire.co.uk/our-products/search?m=1104&pt=1685 and as these can be bought as DIY installations at reasonable cost, I thought it was worth a punt…

So I ordered it, and was surprised when it came as to how big it was and how “professional” it felt.  A cheap ebay import it isn’t – it feels like a commercial grade product, which (as Nuaire do commercial products) isn’t a surprise, and hence the confidence of a 5yr manufacture guarantee.


The above picture shows the unit the grey bit at the front is the heater (with controller electronics on the left) – and the PIV is the green bit (electronics in there) – the white ears are the filters.  Ducting and vent included, the switches are mine.

Nuaire Drimaster Heat

I opted for a Nuaire Drimaster Heat (http://www.nuaire.co.uk/products/catalogue/residential/positive-input-ventilation-piv/drimaster-heat/ ) .  This is a loft-based PIV system with a single loft based unit with an outlet on the landing.  This system (apparently) does:

  • Programmable speed for small or up to 5 bed houses.
  • Clever automatic heat recovery to use “solar gain” if the sun is warming the loft space
  • Auto summer shut-down
  • Air heater if loft air is cold

The air heater is a 500w heater which makes the air warmer if the air in the loft is cold.  This is for “our” comfort rather than any anti condensation functionality as it just prevents cold draughts.

Another benefit is that as the air is sucked out of the loft, it will actually force air movement and refresh in the loft space which of course will help with loft ventilation.

Nuaire have been established for 20 or so years; sell internationally, and also sell commercial grade products.  This inspires confidence in the product and company as I doubt they’d be around so long if it were snakeoil…  The product feels well made, and if nothing else, it is well engineered!  It comes with a 5 year warrantee.

Possible issues

As the air is pulled from the loft, when it is very cold, then very cold air will be blown into the house.  This is minimised with the heater, but of course it is still sending in cold air.  Our stairs/hall are coldish anyway so not overly concerned, and I’m guessing this is better than open windows in each room anyway.  In my experience, when the heater is on the loft can be cooler – so personally I’d not want one without the heater.  Remember though the heater takes the chill off the air (on thermostat) only – it isn’t a fan heater – and it won’t blow out hot air!  (My laser thermometer does show the air coming out is roughly the expected temp)


The kit comes withSam_1929[1] everything you need, bar some suitable cables, but I’ve opted to wire it slightly differently.  I’ll use 2 double-pole fused isolators, one for the entire unit, and one just for the air heater.  This will mean it complies with regs having an isolator, but also I can enable/disable the heater if I desire without affecting system functionality. (if I find a spur-timer cheap enough, then I’ll install one for the heater to prevent the heater running overnight).

The rest of the install looks a doddle….!

  1. Cut a 225mm hole in the loft ceiling suitable for the output vent.
  2. Mount the brackets on suitable joists
  3. Fix unit to brackets
  4. Connect and seal ducting tube
  5. Cable up as necessary

Sam_1931[1]I connected it to a fused spur off the lighting circuit as this was more accessible in the loft and isn’t as naughty as it sounds as, for example, shower extractor fans and shaver points are run off the lighting circuit.  The Drimaster Heat is fused at 3A but pulls a maximum of just over 500W, and as the lighting circuit is 6A and all our lights are low power, there is plenty of capacity.

Once installed, we set it to speed 4 (of 6) which is the right speed for our size house, and this seems to pull a constant 16W to run the fan which equates to 4p per day (excluding heater).   Pending success or otherwise, I may reduce speed to 3.  (4 = 40 litres of air per minute)

All that can be seen in the landing is a fairly discreet and flat vent, and the isolating switches.  Once the ceiling and landing is finished and decorated it will blend in fairly well.

In the loft, the grey bit (between the green bit and the flexi pipe) is the heater, and clearly I’ve ensured there isn’t any insulation touching or close the heater enclosure, even though its not that high powered or likely to be a problem.

Overall, a nice simple install, and now see if it works…..



Does it work?

The system works, and you can feel a nice amount of air movement.  The fan is very quiet and completely non intrusive.  We installed it as per the instructions and do not have a noticeable draught.

After a few hours

Placebo effect or not, the upstairs landing definitely felt fresher, so if nothing else, the system moves more air around!  The landing does feel a bit cooler, but not colder….   We’ve closed half of the upstairs windows and will see how things look in the morning…

First day

Well, the upstairs landing is definitely cooler and fresher.  I guess a thermometer would show it being colder, but it doesn’t feel cold.  Weird, but guess its the humidity change.  Overnight we closed 1/2 the bedroom windows, and in the morning the windows were still a bit condensated 🙁  So no magic solution after the first night.

5 days later

After being out for a couple of days, we came back and the hall/landing was still fresh.  Maybe we need to turn the speed down a bit!  But, we have closed all windows upstairs (and we don’t have trickle vents).  As such, the bedrooms are definitely much warmer.  The first night back we slept with the windows fully closed which would normally mean wet windows, but on the first night back (day 5) the windows had a light mist only on the bottom 1/4 of the window.  And by light mist, I mean as if you just simply breathed on the glass.   It was however a warm night in the bedroom 🙂

The next day it was 0’C outside, and with windows closed would normally result in very wet/condensated windows.  However, in the morning the windows were 99% clear of any misting or condensation. maybe 1cm high light mist at the bottom.

Bizzarely I’m still not convinced lol!  But the last 2 days have been mightily impressive.  Just need to monitor to ensure it is working as it still feels too good to be true.

The cooler landing isn’t an issue as the bedrooms are definitely warmer, and we’ve opted not to use the built-in air heater just to see how it goes.  (update:  over the winter months we now do have the heater on for OUR benefit to stop the landing getting cool)

So, 5 days in, looking good….

Update 30 October 2013

Well there has been a lot of interest on this page, and a fair few people asking how it has gone and if it works, so thought I’d do an update.

Its interesting as, as you know, I’m a sceptic 🙂  We have at last decorated the landing so the system is now much more discreet.  Its been on 24×7 and the heater (which I’ve got on a separate switch) was only on during the very cold winter.

Its hard to say for 100% certainty if it works as no two nights are the same humidity or internal/external temperature, so the scientist in me hasn’t yet proved it.  A mild October doesn’t help comparison.  BUT – since installation we have NOT had to wipe any windows down at all.  Last night (Wet and 5′ outside), we have 2-3cm of LIGHT misting at the bottom of the window.  (prior to installation it was thick misting all over that would run off and the sort you could wet a towel on – but we’ve had nothing like that).

The mould we did have (fresh and small black dots) has gone or gone grey and easily wipes off.

We have checked, and there is NO mould behind any furniture or wardrobes etc.

BUT – we’ve also learned about condensation and made other changes which all help:-

  • We fitted a powerful shower extractor fan (vented externally), and leave the bathroom window open for a few mins after a shower, and close the bathroom door.  We also have the temp a bit lower.
  • We’ve had the house re-roofed (not related!) and this meant a new breathable felt membrane and also meant we could add insulation to otherwise impossible to get at areas in the corners of the rooms.
  • We leave windows on “night” settings in rooms we have the heating on low (e.g. guest room)
  • We use the cooker extractor fan (vented externally) when cooking
  • We have had a log-burner installed (which when used sucks moist air from living area and uses it thus removing moisture)
  • We have installed vents in other chimneys that were bricked up
  • We leave the bedroom door slightly ajar most of the time (though we close when guests stay and its still okay)

So the Nuaire Drimaster is only part of the changes we’ve made – and hence hard to say 100% if it does the job by itself.  Oh – and we altered the default program so it goes into “heat recovery mode” when loft is 18′ or more which is lower than normal, and set the heater to only come on <14′ over winter, which suits our install.

SO – the bottom line is – I can’t 100% prove it, but from a week after installing, we have not had to wipe down any windows or had any condensation issues……..

Would I buy and install again – yes.

Update March 2014

After Darren took the time to post in the comments section, completely unsolicited, I thought I would also give an update.

After decorating we found evidence that mould had been covered up and bodged by previous owners.  However, after decorating and with this system still running, we have had NO mould appear, walls dry, and windows only “very minor” condensation on a cold night – and that is with windows locked closed (so minor, windows not wiped or opened).

Over winter the loft air is cool so the heater takes the chill off but (of course) uses power to run – 500W, so max 12kwh a day, £1.50 max?  Of course it isn’t on full all the time (automatic), but maybe £20-30 a month over cold winter months.  Still cheaper than fixing mould!  And of course the heater is for OUR benefit, not to help with condensation.  The reverse, when the sun comes out the loft gets hot and we’ve tuned the Nuaire to go into “high speed” mode when loft is >18′ – so when sun on roof we get “free” heat blown out.  Also as air is “better” the heating is probably lower than it used to be for the same comfort.

We’ve decorated the landing now so the unit can hardly be seen and its just forgotten about and it quietly gets on with the job.  Still happy with it, and it still works….

From Darren (see comments):  “Just wanted to say thanks to Ryan for this blog, it helped persuade me to purchase a drymaster heat which has been running since early December. My house suffered really bad with surface condensation on windows, walls, behind furniture, mold etc. Thought I had rising damp at one point but after research and reading this blog heard about PIV. All I can say is that this system has totally cured our problem. Since installing I have not ONCE had to wipe down windows at all. This is amazing as our windows were normally saturated every morning in the winter months. I cleaned all the mold off the ceilings and walls after a week of installing the unit and to my amazement it has not come back whatsoever. The house feels fresher as all the stale air is constantly pushed out of the house so it is just a nicer environment. I will mention that you will notice the landing will be a bit colder due to the fresh air being pumped into the house, I could turn on the heater but have not felt the need so far. For people asking about settings it depends on your house, installation and severity of problem, I have a 4 bed house and suffered terribly, I initially had it on setting 4 but have recently turned it down to 3 and it is still working fine. I have also been able to turn down the heating thermostat as its so much quicker to heat the house due to much lower moisture.

I got a sparky to fit it and it was real simple for him. I purchased a heavy duty chain and hook from screw fix for £10 and hung mine from the rafters, it really works well and means no vibration. I would recommend anyone buying one to do the same. I also like Ryan run the heater off a different switch in my airing cupboard, that way if I need the heater on its simple to do without climbing into the loft.

I really can not say enough good about this system and for anyone wondering if it really works, it really does. Would I buy one again, 100%

Update October 2014

So, its 30 October 2014 and I’ve just turned the “heater” part back on as its getting cooler.  The heater has been on for just over a week and using an extra couple of units a day, but nothing too much and even then cheaper than dealing with mould.  But the system has been on all summer and still, house is mould free and even checking behind units its fine.  So still really happy with it.

I thought I’d better upload a pic of the final install as the picture above makes my house look like a building site!  It was, but once decorated the unit is very discreet.  The lighting is poor and the photo makes it look more obtrusive than it is its the early morning shadows- in fact its barely noticeable and visitors seldom see it, and as its quiet they don’t hear it.



TOP TIP (painting over old mould)

When redecorating we had one corner that use to be very mouldy, and previous owners clearly bodged it which meant that I could not paint over it – standard emulsion would just not dry.  No idea what on earth they did!

So, another top-tip from me is to buy some Zinsser BIN (B-I-N).  This is a special paint which is expensive, but it does what it says on the tin.  Basically, you roller-paint it over any problem areas (like mould, old water damage, rust marks, rusty nails embedded in wall, old chemicals/gloss paint etc) – and go for a cuppa. After 45 mins its dry and you can emulsion over it as normal (!).  Yeah – really!  It is a must-have for every old house.  I’d recommend a cheap foam roller set from Poundland as the roller will need binning after use.

Where I’ve used this, the emulsion paint has been perfect, and no marks have come through.

Final Update, November 2018

What can I say that hasn’t been said before!  5 years on, and still the device seamlessly prevents our condensation and mould issues.  Why wait!


Please note these comments were made by genuine posters on my blog here, and were copied from there to here to retain their valuable contributions.

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