Positive pressure ventilation loft units – Which?

Hi all…. Holy thread resurrection batman! Seems you lot may know a bit about these piv systems… I am just about to install one but have 2 potential locations to consider. Below is a high fidelity engineering drawing of the two potential locations on the upstairs landing. I am not sure whether it would be best nearer the bedroom or more central…. Any suggestions anyone?

Not too crucial where you locate the outlet as far as operational effectiveness is concerned – the PIV unit is gently and continuously pumping fresh air into your house so anywhere convenient on the landing ceiling will be OK. However, you want to keep it away from any smoke alarms – you don’t want the air flow forcing smoke away from the sensor!(Nuaire recommend 1 metre for the Drimaster, but you may be able to get away with less, depending on the fan speed set on the unit). Also, bear in mind, if the outlet is close to a wall or above a door, it can send a draught downwards (again, depending on fan speed and distance) which might cause a nuisance. The Drimaster outlet blows air out in 4 directions, across the ceiling. Up to 2 sides can be blanked off (foam inserts supplied) to overcome the smoke alarm/wall issues to some extent. Ultimately the further the outlet is away from walls, the less chance of nuisance draughts.

(Note: I fit a lot of these in my line of work, so am commenting from personal experience of approx. 100 installations in all manner of property types. Shove ’em anywhere – they work!! Hope this helps)

i would go with the more central one. not seen your house, but from the engineering plan it looks like a location where it would draw air easier from downstairs also .

Dudie and Mac appreciate the replies guys! Thanks. The more central one is what I was thinking (planning to move the smoke detector as you mentioned) and blanking off the two sides of the diffuser nearer the walls / door as a starter.

Cheers!

Why can’t it go more in the middle of the stairs? Then you are more likely to avoid draughts etc? I’m guessing it’s due to what you have in the loft ?

If I stick by the stairs funky Dunc then there is hardly any space around diffuser (weird cupboard thing above stairs. So only one side would be clear. If I stick central then there are two long hallways with no restriction (manual states you need up to 1m clearance on fastest setting) I guess it would still work but as dudie mentions suggests downdraft would be an issue.

Also I would have to install under the ch / cw water tanks which would be a bit of a pain 🙂

Just wired the unit up to a spur and seems that pretty quiet! Only annoying thing is that the fan blade was catching on the plastic case….. So popped filters off and centralised the fan. Should not really have the do that on a brand new unit! But it’s all fine now. Pretty poorly made if I am honest…. Cheap plastic housing which does not fit together well. Will see how it goes tomorrow when I install.

This thread is making me very interested in a PIV unit. We get a musty smell in some of the upstairs rooms and a bit of mold on one outside wall in the lounge behind furniture where there is limited air circulation.

One thing that worries me though is that we definitely get condensation at times in the loft on the felting on the underside of the roof. I can’t see that pumping air from the loft in this situation is going to be a good idea as it obviously isn’t that dry. In the loft with the light off I can see slivers of daylight entering under the eaves so there is some kind of ventilation up there.

Maybe condensation in the loft is a sign something is not right with the insulation/ventilation up there? The musty rooms are under the loft space thinking about it.

Any advice?

I’ve bitten the bullet and ordered a Nuaire Drymaster. Every winter our windows are soaked and we have a constant battle with mould so hoping for the miracle-cures that others have described!

Just concerned as to how cold it’s going to make the house…

Hopefully installing it this weekend.

I thought this thread was about positive pressure units. I was going to suggest Pascals. Or maybe go crazy with inches water gauge.

Just concerned as to how cold it’s going to make the house…

not really.

I’ve bitten the bullet and ordered a Nuaire Drymaster. Every winter our windows are soaked and we have a constant battle with mould so hoping for the miracle-cures that others have described!

Just concerned as to how cold it’s going to make the house…

Hopefully installing it this weekend.

I think the more recent thread on these bad boys is here;

http://singletrackworld.com/forum/topic/nuaire-drimaster-heat-experiences

Thanks Timmys, I found that thread after I posted 🙂

In your last post you seemed to be having mixed experience with it, have things improved?

EDIT: Actually, if you have an update it’ll prob work better in the other thead… I’ll keep an eye on both 🙂

I installed the nuaire heat back in november in a small 2 bedroomed house. These are brilliant !!. Never open windows now. House is near bone dry. I use setting 2. I never use the heat option. I suggest a normal drimaster and use your central heating with it. Very slight breeze at top of stairs.

I am a chartered engineer and had tried everything to sort the damp.. all added up a bit (trickle vents, bathroom in line fan, cooker hood,washing out on line etc) but nothing was really sorting it. Trickle vents actually made it worse as they drop the temperature and so lower the dew point. Then came the nuaire drimaster…. brilliant!! Believe the hype and buy one. I was very sceptical of these based on all the amazon reviews etc but i am so happy with my purchase.. problem solved.

These are all relative humidity, which is % moisture at a given temperature. So it is often 90% relative humidity outside in uk over winter, but that’s air at 5degrees. The fan draws that 90% relative humidity air in through the slates, soffit vents or breather slates and pumps into house. As it flows in the temperature rises and therefore the relative humidity drops to 50 to 60%. Where as trickle vents, hit and miss vents and windows open just drop the temperature and therefore can raise relative humidity a bit. This is general and other factors are also involved.

Thanks Timmys, I found that thread after I posted

In your last post you seemed to be having mixed experience with it, have things improved?

EDIT: Actually, if you have an update it’ll prob work better in the other thead… I’ll keep an eye on both

I might as well update here rather than bumping the other one.

Overall I’m pleased with it and three months down the line the ‘problem’ room has lost its funk. Looking back at my previous updates the problem room was at 70-75% humidity and now it is normally 55%, perhaps getting up to 60% on a bad day. That’s with dropping the Nuaire fan level to 3 from the 4 I started at.

I’m not sure if the improvements are due to the loft drying out or it’s because we entered the time of year when the central heating started coming on.

The house is defiantly not bone dry but it’s certainly improved. There’s a window in the living room that has condensation on it most mornings still.

I’d still appreciate feedback on whether I’m best keeping trickle vents above windows open throughout the house. Currently they are all open to maximize air flow but perhaps I should be keeping some or all shut to maintain higher positive pressure through the house?

Thanks for the update, sounds promising.

Update: I fitted it on Saturday morning with no major issues.

Worst part of the installation was cutting the hole in the lathe-and-plaster ceiling, I eventually found my jigsaw worked the best, although it was awkward to use upside down. Tip for others, the template they give you to cut around is too big by about half an inch, not leaving enough lip to drill the securing screws into… I ended up attaching battens above the hole in the loft and using longer screws into them.

I initially set the Drimaster to fan-speed 5, just to blow the cobwebs away and get things moving. It was bloomin cold so I soon turned it down to 3!

By Sunday morning, most of the upstairs windows were much dryer than usual, with just the worst room (daughter’s bedroom) still having a fair bit of water on, but even that was better than usual.
Downstairs still had a fair bit of water on the windows, but they were also better than usual.

Today, even the window in my daughter’s room only had an inch-or-so of condensation, and the downstairs had further improved. The dehumidifier that we usually run over-night hadn’t switched on, presumably its humidity sensor thought the air wasn’t damp enough for it to be needed!

I’m hoping for the last of the condensation to have gone tomorrow and I might knock it down to setting 2.

Yippee! After 16 years, a dry house!

I’m still trying to persuade my parents to get one of these. I have sent them link to the website & mention it every time I see them.

All their windows get very condensated & they turn radiators off in rooms when they aren’t being used, which makes all the surfaces cold & the problem worse…..

I’m tempted to just buy them it & take it round there……!

1. Close all trickle vents definitely. You will be dropping the inside temperature. The air will find a way out elsewhere.

2. You need to keep all internal doors half open. This is a ventilation system which needs to circulate.

Thanks for the tips. Our double-glazing pre-dates trickle-vents so no worries there.

Throughout the day we keep the internal doors open, but the lounge and daughter’s room are shut on a night to keep the cats out. Hopefully that’ll be enough for the magic to still work – from what I’ve seen so far, it should be.

Had mine in for a year now I think. It’s amazing and I would urge anyone with condensation and mould problems to get one. We used to have mould on ceilings and corners of rooms, clothes in the walk in wardrobe would be musty even our bedroom wall would be wet in the morning on cold nights. Now it’s all gone, redecorated and no new mould has grown. Slightly chilly on the landing but well worth it and I don’t hang out on the landing anyway!