Our house is a 1933 detachached house, with cavity walls without insulation, and modern-ish double glazing. We have a slight issue with condensation in that the bedroon windows get wet overnight, and we’ve noticed a couple of small patches of mould on cold external walls. Its quite a minor issue for us, but pretty much down to the modern way of living – warmer air with central heating, and not as much ventilation due to double glazing; bricked up fire places; and roof insulation. (using and venting the fireplaces is next!)
If we leave the bedoom windows open a notch, there isn’t condensation which sort of proves the point. For more information on the causes of condensation see http://www.diynot.com/wiki/building:condensation_in_houses
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 plastic car 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 miricle 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…
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.
(Available on Amazon, but I bought elsewhere for £306 delivered with 10 year warentee)
Nuaire have been established for 20 or so years; sell internationally, and also sell comercial 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 warentee, and the supplier I used added on another 5 years (though not seen any paperwork yet!)
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. Time will tell.
The kit comes with 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….!
- Cut a 225mm hole in the loft ceiling suitable for the output vent.
- Mount the brackets on suitable joists
- Fix unit to brackets
- Connect and seal ducting tube
- Cable up as necessary
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 celing and landing is finished and decorated it will blend in fairly well.
In the loft, the grey bit (between the green bit and the flexy 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 higjh 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 noticable draught.
After a few hours
Placebo effect or not, the upstairs landing definatley 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…
Well, the upstairs landing is definately 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 definately 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 lght 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
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 definately warmer, and we’ve opted not to use the built-in air heater just to see how it goes.
So, 5 days in, looking good….