[Closed] Positive pressure ventilation loft units - Which?

Bump - interested in this too 🙂

I'd be wondering how much that heating fucntion is going to cost to run.

If you google both there are quite a few discussions about both of the above, the different flavours of each and comparisons between them.

I think someone said, there's not much different between any of the branded units.

The other option is a company called EnviroVent (who get quite a few reviews on the web), who do not appear to sell the units separetey but will come and fit...at a price !

ie it looks like their equivalent fitted is £600 +

see this thread: http://singletrackworld.com/forum/topic/too-much-loft-insulation

see this thread: http://singletrackworld.com/forum/topic/too-much-loft-insulation

That is the OPs original thread 🙂

After much googling, the winner is.... Nuaire Drimaster Heat for £300.

Why? Because its cheaper than the Xpelair. The replacement filters are half the price of the Xpelair. The heater is also wired separately so it can be easily turned off. Also their customer services were very good when I spoke to them and even pointed me to where to buy a unit cheaper than they could supply it.

Will be ordering tonight.

before you spend 300 quid i assume you have tried plumbing back in your extractors in the kitchen and the bathroom and solved the issue - it may be 300 quid wasted if the ventalation is not the issue.

Trail-rat - Our cellar was converted to a kitchen/utility/snug about 5 years ago. Long story short, the kitchen general extractor had not been plumbed externally, the extractor was just extracting in to the roof void above the kitchen 👿 to sort now would mean open up the kitchen ceiling plaster board and drilling a hole through to the outside.

So for now I have switched it off, and will move that extractor to the bathroom as it is a good one if humidty on/off settings, rather than just operated via the light switch.

I am also considering fitting a (as described to me) a trickle extractor that remains constantly on, which will hopefully pull air through the cellar area. This can be fitted in the utility room where there is an existing extractor. ie no mess or costs of knocking holes in walls etc.

I still want to go with the loft fan option. My son has had continual hospital admissions for recurrent pneumonia/respratory problems. All the reviews I have read have said if nothing else these units do clean the air quality.

Our house had the bathroom extractor ducted into the eaves of the house just above the soffit but no further, so it was just making a corner of the loft damp... who the hell installs these things like that?! What are they trying to achieve?

I'm glad it was a cheap nasty thing so the fan packed up shortly after we moved in, or it may still have been doing it now...

to sort now would mean open up the kitchen ceiling plaster board and drilling a hole through to the outside.

I'd have (without knowing your house ofc) that this would be a more effective option, and not so far off in cost? If the roof unit doesn't work out you might have to do it anyway.. I got a 100mm core bit from Lidl for about £30, had to borrow a drill man enough for the job though!

@funkydunc - let us know how you get on with the unit (either on here, or via email - see profile). Am v interested. Don't have the same level of problem, but would like to keep the humidity down from the 70% it got to late summer!

70% we don't get below 85%!

Update as requested

I ordered from dryhomes.net who were very helpful, even sending their own version of installation instructions, which in many ways were better then the Drimaster ones. The unit was actually sent direct from Drimaster.

Fitting was simple and straight forward... apart form having to take down lots of shelving in the loft, and removing the loft boards. The Heater unit uses a separate electrical supply from the fan unit, and they do not supply electrical cable, I guess understandably they expect people to get an electrician in.

Does it work ? Hell yes !! I have a cheap £5 humidity meter, and prior to the PPV system I was averaging 80-85& relative humidity in the bedrooms, tonight its down at 60% Ok this might not be that accurate, but other things have changed.

The air feels much lighter and much fresher, sounds daft but true.

The mold that covered the tiles in one corner of the upstairs bathroom has turned from black to grey and is turning powdery.

Jnr FD has a bath at night, and the next morning the window would still be wet with condensation. It now goes that evening.

The Travertine tiles in the down stairs bathroom never used to dry out apart from in the middle of summer, they now do in a few hours.

Noise is minimal, if you stand on the landing, you can he a gentle whirring noise, but you really have to listen.

At the weekend it was sunny, but cool enough for our heating to kick in, however it didnt. It would appear the heated air in the loft space was warm enough to keep the house warm enough to not require the heating.

Down side - We have the heating set at 20 deg, however now the air is dryer, that 20 deg 'feels' cooler. Mrs FD has asked for the temp to be increased, so I have put it up 1/2 a degree 😆 hopefully the saving in heating the house from the air not being damp will compensate for this....

The other downside is that our landing is quite small 2 x 1.8 m and it has become quite cool, and I am sure it is slightly cooling Jnr FD's room, which was already cooler than any other room in the house. It does concern me how cool his room will become in a really cold spell (hence the heater)

The heater element isn't wired up yet, but following google advice I will have it on a timer for early morning and bedtime.

Overall - We are definitely seeing a big benefit already. OK we haven't had a really cold night yet since installing, so I will have to wait and see on that, but for it was definitely worth the cash, and fingers crossed it will have health benefits for Jnr FD.

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Hi

I think it might have been my suggestion so glad it helped, and sorry I never revisited the old thread!

We have the Xpelair and my parents have the Nuaire (neither with heater). Both have been almost silent and faultlessly reliable for +5 years.

Like you say - for such a simple and relatively cheap product the difference is very immediate.

The Xpelair filter is a fairly simple sheet so I just bought a few metres of filter material from RS.

Would be very interested about how the heater works out - can you drop me an email in a few months when you've had a play in proper cold weather? (email in profile) How many watts is the Nuaire heater? (I've been considering adding one of the small tube trickle heaters that are only low wattage).

Also, where is the heater situated? If in the main body of the fan, then might be better to insulate the "trunk" 🙂

Great update funkydunc - I shall definitely explore this avenue in our house.

It's a shame isn't it... when coal was cheap and every room had a fireplace these ventilation problems wouldn't have existed, as so much air was being dragged up the flues.

Further update.

Still working really well. There was a ground frost last night (not sure if it was below zero) and woke up to no misted up windows where as neighbours were covered.

All mold has gone and so far shows no signs of returning, early days yet though I guess.

3/4 weeks on and the humidity is still lowering, although that could be coinciding with less humid atmospehric conditions. I may even turn down the fan setting.

The best outcome so far though is Jnr FD. He has had 2 colds since installation. Normally this would have developed in to full on Pneumonia and hospitalisation for the little man. There is no way of proving anything, and it could all be coincidental, but both Mrs FD and myself beleive it is having a positive effect on his health. The colds he has had would normally land him in hospital, but not this time.... 😀

good stuff. Do you have it running through an energy meter to see what juice it's using?

Hmmm, this looks ideal for the sandwicheater household.

Do you have it running through an energy meter to see what juice it's using?

No, but that would be a worth while task. Would have to get a meter from some where first and wire it in to the circuit...

"Would have to get a meter from some where first and wire it in to the circuit..."

no wiring needed - just clip the meter sender round the feed to the unit and the reciever will tell you want shes suckin.

No, but that would be a worth while task. Would have to get a meter from some where first and wire it in to the circuit...

Most electricity suppliers will send you a consumption meter now, you can just see the difference on and off.

Where is the air being extracted from? Is it vented into the roof?

I have no need for this device, but am finding it strangely compelling 🙂

EDIT: Duh, I mean where is the air being pushed too..

[i]Where is the air being extracted from? Is it vented into the roof?[/i]

Took me a while to work it out.

It pumps air from the roof void into the house.

Theory is that air in the roof is less humid than that in the house and by 'overpressuring' the inside of the house that humid air is forced out through gaps round doors/up chimneys etc.

Having been plagued by condensation and mould for too long, I have just ordered one of these!

I'm thinking about something similar. just need to work out where would be easiest to get power from.

Down side - We have the heating set at 20 deg, however now the air is dryer, that 20 deg 'feels' cooler.

That's the wrong way around, drier air should feel warmer.

What about if you have an unventilated loft space? My soffits & fascia are all flat plastic.

What about if you have an unventilated loft space? My soffits & fascia are all flat plastic.

Apparently if you get in the loft with the hatch closed and can see daylight coming in then that's sufficient leakage for it to work.

Is this kind of unit compatible with a loft extension? Our loft space is soon to be converted into another bedroom, and so will be sealed up pretty tight. We have a dehumidifier going downstairs pretty much constantly, but it doesn't really seem to touch upstairs - windows are pissed wet through in the boys bedrooms (cold side of the house).

Stopping them breathing isn't really a solution 😉

Thinking about it then, these units take air from the loft, filter it, blow it into your house and displace the existing wet air. If the loft is above inside temperature it blows hot(ter) air into the house (but too hot and it shuts off), if the loft is colder it blows cold air into the house unless you use the 500W heater to prewarm the air. Surely neither of those are ideal? A dehumidifier takes the air that's in the house, filters it and extracts the water, isn't that better?

Thinking about it then, these units take air from the loft, filter it, blow it into your house and displace the existing wet air. If the loft is above inside temperature it blows hot(ter) air into the house (but too hot and it shuts off), if the loft is colder it blows cold air into the house unless you use the 500W heater to prewarm the air. Surely neither of those are ideal? A dehumidifier takes the air that's in the house, filters it and extracts the water, isn't that better?

Their point is that the loft is warmer than the outside air due to solar gain through the tiles and heat losses from the house below into the loft. So it's more energy efficient than opening windows to air the house.

I don't know how it compares to a dehumidifier but I do know that whichever room of the house has our dehumidifier in gets pretty warm so it's using a fair bit of electricity and it doesn't dehumidify much beyond the room it's in. If a dehumidifier just extracted the water without putting out a load of waste heat then it would definitely better but they're all pretty inefficient.

Fingers crossed!

"If a dehumidifier just extracted the water without putting out a load of waste heat then it would definitely better but they're all pretty inefficient."

nature of the beast that as far as electric heaters go - they are very efficient.

Their point is that the loft is warmer than the outside air due to solar gain through the tiles and heat losses from the house below into the loft. So it's more energy efficient than opening windows to air the house.

Maybe in Summer, but in Winter our loft is very cold compared to the rest of the house!

Took me a while to work it out.

It pumps air from the roof void into the house.

Theory is that air in the roof is less humid than that in the house and by 'overpressuring' the inside of the house that humid air is forced out through gaps round doors/up chimneys etc.

Embarrassingly, I used to have one in my last house too! I was always slightly puzzled by it, but it did also help with balancing warmth around the house (and with storage heaters you need all the help you can get). It was a newish place so it's hard to say if it was effective, but I certianly didn't have any damp problems there.

Maybe in Summer, but in Winter our loft is very cold compared to the rest of the house!

But is the loft very cold compared to the outdoors?

But is the loft very cold compared to the outdoors?

I would [i]assume[/i] so, I may be about to be proved wrong though.

On a slightly different note, has anyone tried, or had any success with single room HRU's? Thinking about replacing my standard, rubbish bathroom extractor with something like this;

http://www.envirovent.com/home-ventilation/products/heat-recovery-systems/heatsava/

[b]£340ish[/b]

or

http://www.vent-axia.com/product/lo-carbon-tempra-htp.html

[b]£150ish[/b]

both are retrofittable, constant trickle, humidistat boosted.

Thanks, Ben.

If you draw air from the loft then I presume the loft draws air from outside. What happens when the humidity is greater outdoors than indoors? I know the relative humidity will fall as the air is heated but still?

Indeed, a dehumidifier (refrigerant) is >100% efficient!

But is the loft very cold compared to the outdoors?

About the same temp - all the eaves vents means it has a nice draft running through it and is pretty much the same as outdoors unless there's no wind, in which case it might be a few degrees warmer. I certainly wouldn't want to blow air from it into the house.

What about if you have an unventilated loft space? My soffits & fascia are all flat plastic.

Do a bit of Googling, there are ways to vent any loft space, might get expensive though.

That's the wrong way around, drier air should feel warmer.

No it doesn't. When its warm you sweat, if its humid your sweat cant escape so you feel warmer. Lower humidty allows sweat to escape easier, so you feel cooler. Even sat doing nothing in a house at 20 degrees the same effect is happening.

As to the loft space temperature and humidity, I dont think the idea is that you have a breeze blowing through the loft. The fan will lower the pressure in the loft, sucking air through, but not even noticeable. The system wouldnt work if the air was moist, its the fact that the air in the loft is stable and dry that it works.

Solar gain and heat from the house dry the air out in the loft, and then you put that in to the house. All the sites say if you have damp beams in the loft, and open water tanks, condensation on the roof lining etc then the system wont work.

Dry air takes a lot less energy to heat up though, so it's still a benefit.

I've just installed one of those vent-axia Tempra things in our utility room; we dry all our washing in there when we can't hang it outside (most of the time) and even with the window cracked open all the time it could be quite a humid place, with condensation on the windows and the side of the freezer and clothes that took a while to dry.

It's only been in since Sunday but I hung up a whole load of towels to test it and they were dry in two days, no condensation anywhere and it's a lot warmer than leaving the window open. Sticking your hand underneath it you can feel the incoming air is much cooler, but not as cold as outside, so it seems to do what it's meant to.

The only down side so far is it's louder than I thought it would be; if you're in the kitchen next door it sounds like the fridge is on. It's fine for what we want it for, but I could never cope with it in a bedroom, for example.

I thought about the heat-sava, it's continuous speed adjustment sounds clever, but just couldn't justify the huge price difference over the vent-axia.

Both of them have a very low boost rate compared to a normal extractor fan, so I'm not sure how good they would be in a bathroom; it would be dry after a while, but in the short term it could still be very steamy.

Phill why didn't you just buy a tumble dryer? Which would be better for the clothes and getting rid of the associated water.

Air inside houses is almost always more humid than outside because people breathe cook, wash and shower. The relative humidity is kept below condensation point by heating.

An exception is hot humid days in Summer when it's much cooler inside than out and condensation forms when hot, humid outside air meets cool inside surfaces.

To keep humidity down dry towels, bathroom mats etc. under cover outside rather than on a heated towel rail and mop up the bath, shower and sinks after use. Simmer rather than furiously boil vegetables.

To keep humidity down dry towels, bathroom mats etc. under cover outside

We just leave all the windows open during the day (even in winter).

No it doesn't. When its warm you sweat, if its humid your sweat cant escape so you feel warmer. Lower humidty allows sweat to escape easier, so you feel cooler. Even sat doing nothing in a house at 20 degrees the same effect is happening.

But I'm not sat sweating in my house. The converse argument goes: if you're outside in cool weather, and it rains (100% humidity), you feel colder. The water content of the air (just before rain) can extract more energy from your *hot body* than dry air.

The system wouldnt work if the air was moist, its the fact that the air in the loft is stable and dry that it works.
Solar gain and heat from the house dry the air out in the loft, and then you put that in to the house

The system can't do anything about the humidity of the incoming air, air in the loft can't be dried. Solar gain/heat loss can however raise its temperature, which lowers its relative humidity, which may well be 'dryer' than the air in the house so I'm kinda happy with that argument.

Air inside houses is almost always more humid than outside because people breathe cook, wash and shower.

Unless its raining, or foggy... Have a look at the [url= http://www.weatherthurgoland.talktalk.net/trends.htm ]trend[/url] from my weather station from the last 24hrs.