Should you buy a PIV? The pro's and con's of positive input ventilation systems. Vent Axia Review
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- Опубликовано: 6 июн 2024
- We have owned the Vent Axia PIV for three months and in this video, I share with you an unbiased review of how we are finding the PIV system so far, what I like about it, what I don't like, and whether you should get one. I also offer some alternative methods for reducing dampness and mould in your home.
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I just opened my front and back doors - timed for 5 minutes exactly. The humidity dropped by 9% (NINE!!) percent !!!! Talk about game changers, thanks man.
I installed a Nuaire PIV with heater some months ago now…it basically the same as yours, just a different make. In addition, I also cored two vents in the house walls as there was only one at the front of the house, and I assumed one had been removed when a small extension was built at the back of the house. As the house had cavity wall insulation added too, and there were no trickle ventilators in the double glazed windows, air movement in the house was almost not existent. When the coldest and wet weather arrived, we were hit by massive condensation issues and black mould on external walls…behind furniture, beds, and on ceilings adjoining external walls… at times you could see water running down walls… bad… we also replaced the extract fan in the bathroom which was very poor, with a much better extract fan, and extracted through a roof tile extract, and not through the wall as previous, which seemed to work better… the two cores cut had adjustable vents installed, left half open all the time, and the PIV when fitted made an immediate impact, lowering the Relative Humidity in the house from over 75, down to 55/58 with the heating set at 18.5°C. Condensation on windows internally has gone from whole windows misted and dripping, to occasionally a little bit of misting over say 10mm at the bottom of the bedroom window in the morning…we have blinds on windows too now, so air can circulate around the windows inside too, as opposed to heavy curtains which tended to block any air movement around the windows making the problem of condensation on the windows much worse…when the Nuaire was first fitted, and even though like yours it has a heater, we too noticed a little cold draught, but this was simply resolved by raising the temp of the heater by 2°C… We don’t have a window open in our room at night as the vent is half open and the PIV also helps move air, as the input raises the pressure in the house, and therefore pushes air through and out of the vents so ridding the house of moisture laden air from inside… The PIV has certainly done a great job, no more condensation except the very smallest amounts, which is a complete turn around to how it was, and no more black mould growth has been spotted. So no more health risks… Would I recommend these PIV units…Absolutely, I do…when I first saw them on the internet I was a little sceptical, but did some more research and came to the conclusion that it might be the answer we were after…and it was… so, so far, I’m very impressed…and grateful too that I took the time to look, found out and researched it… I’m very pleased now that we did and got it fitted… THEY REALLY DO WORK…
I live in Switzerland and 'Stosslüften' is the national pastime here, too. The idea is that you're changing the air quickly and not losing heat. The heat is stored in the fabric of your building; walls, floors, furniture etc. Not in air which isn't very good at storing heat. As you say when you rent a flat here it's in the rules of the building printed on the wall how long and how often you're required to 'air' your flat at different times of the year. Almost all new houses are designed with an HRV system. For old houses that have been modernised with better sealed windows and doors, they recommend a decentralised HRV system. That means an individual HRV unit in each room. There are some pretty neat looking units available. Your video was really informative and interesting, well done!
I think irrespective of the humidity levels in inside or outside air, a good PIV unit works by moving the air around and not allowing moisture to settle. At least I understand that to be the central message of the excellent videos that Peter Ward has posted on YT. He uses two units to pull in and extract out air in his cellar, which was very damp, and the result is very dry walls. Worth a watch.
Fantastic video, this has really helped me!
I installed one last week and it was an absolute game changer. Condensation completely gone in 2 days. Yes it's a bit colder in hallway now but I've not noticed the increase in heating use and I have a smart meter ihd to keep an eye on. It's totally worth it!!!
Thanks for the post. Did you install it yourself may I ask? We have had a company do a 'free' mould survey which took them 30 minutes and they have now quoted us £1,350 to install a OIV unit and 'mould wash' the walls, which are not that bad anyway. I'm thinking this is a lot of money and I could buy and fit the unit in a few hours, saving hundreds.
@@davidbrittain3212 WOW these units cost about £330 and take about 15 minutes to fit, your basically paying £1000 to fit, that is daylight robbery
What country are you in?
I am considering buying a PIV unit and found this to be an interesting, informative and helpful review.
I agree that PIVs do not puch air out of the property. There is an insufficient pressure gradient to achieve this. My work some years ago on "negative pressure" and "clean" rooms showed that to maintain sufficiently significant air throughput a far larger fan system would be required. Thanks for your very balanced opinion. I am looking at solutions for my sister-in law, and while PIV might assist I feel there are several things they must do to reduce the humidity in their (old) house in the damp NW. Simple functional extraction in the bathroom and kitchen will be my first suggestion for them and only once that's done (and if inneffective) will PIV be considered.
I have been looking at installing a centralised extractor system that would be piped to the bathrooms and also a couple of centralised vents in a hallway. They extract on a light setting all the time and have built in humidity stats so ramp up the fan when the humidity rises i.e when showering. I think this would do a better job than the PIV as it would be extracting. This would ideally work best with window vents to help pull fresh air in. I see one of the issues with window vent or even having them open slightly is on a damp still night there is still not enough air movement.
Fitted a Nuaire carbon filter, heated version yesterday. 3 bed semi, 2 adults plus dog. Normally get 4 inches of condensation on windows, this morning there was none. The device is running at 3. So far so good, very quiet.
I also swapped out the bathroom ceiling extractor fan and fitted an in line fan instead. My new one extracts 255 cubic meters of air from the bathroom as opposed to 90 using the old one. Even the mirror now doesnt mist up during a shower.
It sounds like a dehumidifier is the way to go. That's what I have. I have a couple of models, an Ecoair Classic and an Ebac one. I find the Ecoair works better to cut humidity quickly but the Ebac works slower and I believe is cheaper to run as I tested it with one of those price meters you put in the socket. I've recently had a new Combi boiler installed in place of the system boiler and tanks I had. The heating engineer set to the boiler to run on 'low and slow' with a weather compensator. Supposedly it keeps the bills lower but the boiler should run constantly but at a very low flame. I have found that once the heating is on more or less all the time the warm air carrying the moisture eventually works its way out of the house. My condensation has been reduced.
At time frame 6:11 you flash outside temperature and humidity this is the end result once that outside air is heated to 20 c
Outside temperature: 6°C
Relative humidity outside: 94 %
Calculated grams of H2O per kg of air: 5.74 g/kg
With the following fields you can calculate the (new) relative humidity if the outside air is heated in a closed space (room, office, factory hall e.g.).:
Set temperature inside closed space: 20°C
Calculated relative humidity inside closed space: 39.3 %
Thank you….. for this I really appreciate your experience…
I had one installed in my Victorian terrace. About a year ago. It did help with the condensation and mould. But I did install better extractor fans in the bathroom and kitchen. Which were the worst rooms in the house. In the front room I believe it got rid of the problem with this being south facing and coolest part of the house. Just wish we had a multi burning stove.
I’ve had a Nuaire in my bungalow for nearly 6 years, I do honestly notice a big difference in humidity in the house if I was to turn it off. We turned the piv off a few months back out of interest and noticed cooking smells hung around a lot longer and also the outside walls would seem damp. You are right however, the built in heater is a waste of time and it certainly makes the landing colder. No mould since fitting it though which is good.
Totally worked for us and was easier to heat. Damp air takes far more energy to heat than dry air, our HP Air Conditioning is running at a lower power draw since installing. No more water on the windows and no more damp ion the walls within 2 days. The heating element version of the Vent Axia is not worth it as it runs at 400w. Cold dry air is easier to heat than damp air. We went from 75% to 82% humidity down to 52% in an 1,100 sq foot property. My wife does not use her inhaler anymore.
We had a humidity problem in our bathroom. Opening the window would cool the room, cause the humidity to condense on the walls, and eventually reach the same temperature and humidity as outside. Running the fan worked while the fan was on, but even after running for a couple of hours, a few hours without it left the room smelling stale. A dehumidifier brought the humidity down from 90% to 70% quite effectively, but struggled to get it much lower, and the room still smelled stale.
I fitted a single, small recuperating MVHR a couple of weeks ago and it's been great. I've set it to run at the lowest speed all the time. At that level we can't hear it at night and can barely hear it even stood directly under the fan. It keeps the room at 50-60% humidity, the air smells fresh, and best of all it seems to make no difference to the temperature.
At the moment we're still using the dehumidifier set to 75%, but I plan to use a humidity sensor to trigger the fastest speed on the MVHR instead.
Would you mind providing a link to the small recuperating MVHR?
I am also considering how to tackle humidity in our home and agree with you regarding the link between the inside and outside humidity. Our humidity fluctuates with the weather as one would expect. It is interesting that the suppliers of the PIV systems talk about bringing fresh air in when often this air is at a higher humidity level than the air inside. We have used a dehumidifier and this has made a difference in terms of the damp feeling in the room.😊 Your review was most helpful.
But it is wrong to assume that because outside air is at higher humidity level of say 80%, it is more guidance than indoor air at 80%. This is not the case. Indoor air at this percentage will carry far far more humidity than outside air due to the usual temperature difference.
Thanks for the video. I live in a basement flat and have been looking at PIV systems (and well any system to reduce chance of mould). The PIV systems for flats are designed to draw air directly from the outside, so I don't really see the point of them as that would basically be like opening a window. PIV systems that go in the attic will draw in slightly heated up air (as heat escapes from below) and that air will "dilute" the air in the house with slightly dryer air (which hasn't had moisture added to it from cooking/showering/breathing). People mention humidity (relative humidity) without taking into account the temperature and they are directly related e.g. it might be 90% humidity and 13c outside but that same air heated up to your room temperature will most likely be dryer.
I would say a PIV system is good to cover up behaviour that causes increased moisture/mould build up.
For example, there are many ways to reduce/stop condensation on your windows. Open trickle vents/keep curtains open/keep doors open/keep window open/double glazing/even bubble wrap - basically increase airflow/ventilation/insulation and the condensation is heavily reduced/gone. The PIV system is the lazy way to do this and will instantly fix people's condensation issues for the most part, however it will make your home colder.
I think a combination of fans and opening windows might be the best/cheapest way for me to counter my mould issues.
I agree, I'm dealing with a static caravan with high humidity based on outside air temp, no overnight heating, winter months where theres high humidity outside and sleeping bodies expelling moisture. I suspect the most efficient solution is to NIV ie draw the moisture out the room ether with extraction and/or dehumidifier. Testing underway!
@Life at Leigh really great video. Wonder if you have review the heat recovery unit?
I fitted a nuaire system myself , and wow it works well ,from memory i fitted a power meter and only uses 14w on speed 3 , there's quite a bit if science involved in humidity which i confess i don't quite understand , but I'm certain if you stuck 100w fan at top of stairs it wouldn't do anything to combat mould/condensation ,because it's just moving moisture laden air around
Your correct it’s not just about movement of air but more to do with pushing the humid air out of the house and replacing with fresh air. The outside humidity is also a red herring as the outside air is colder so can hold less water and therefore have a higher humidity reading. E.g. if the air is 4 degrees outside and 90% humidity then that air at 19 degrees would have a humidity of 35% when heated. So even replacing a small amount of the hot humid air with this will lower the humidity in the house and get rid of damp.
It’s also worth noting that the time it takes to heat the house is significantly quicker when the humidity of the house is lower.
We installed one of these 20 yrs ago (2 installs - first one stopped working after 12 yr continuous) on our modern very well insulated house as it got stuffy and had some condensation on windows as half the house is underground. It stops condensation, keeps the air fresh. In the winter we occasionally turn it off but rarely. It is a heated version but never wired in. Our bathrooms use constantly running fans to further help with the circulation air. However, even this combination will not solve heavy condensation e.g. in a bathroom. For that a small dehumidifier is the simple solution - the cost of running them is easily offset by the lower heating costs of the drier air - esp in our case as the underground ensuite has no windows and the humid air leaks to the bedroom.
I have used a dehumidifier for the last 5 years and although it has reduced the mould issues in the north facing area of the house, it does not eliminate the mould, just slows it down.
A friend has the PIV unit in a house layout almost identical to mine running for the last 12 months and having seen that it works for him I have just installed one.
Many of the comments made I recognise. The heat unit is an expensive add-on for what it does and my colleague removed his since he believed that it was not really doing the job but just adding to the running costs. Also, as you say I believe it’s the circulation of air within the property that actually does the job of reducing condensation on the cold surfaces.
My final comment is that the units are very expensive for what they are and the add-ons available for them also extremely expensive.
However, if it reduces the mould in the house without me having to think about it then I am happy with the purchase.
If it's just about circulating air wouldn't just running a fan work just as or almost as well?
@@DavidLee-cw6ci Perhaps it would, I really don't know. The unit is variable speed via the settings and reasonably quiet in operation. It also cuts off automatically when it senses it does need to be on. After going through a full winter I am extremely satisfied with its operation having reduced my mould problem around all the rooms of my house by I would say 99%. My only comment would be that for what it is, it's in my opinion very overpriced.
OMG, just got to your opening windows either side of the room to create a through draft, even in winter. I suffer from shocking condensation (see previous post) but have found this technique useful in the day, and no point pumping in cold air to a room that's at similar temp as outside (but for air flow reasons), and use a dehumidifier for an hour or so before bed (humans venting moisture time). I'm planning to extract moisture during the night at source using quiet low power consumption fan
I fitted Nuaire Drimaster PIV unit (heated version) I concur with your experience, It has practically eradicated condensation since fitting it, and yes the landing area is colder in winter but that is a small price to pay to prevent excessive condensation that in turn causes mould growth. I'd rather have a slight chill than having to re-decorate rooms (notably North facing rooms) every few years due to mould staining. Is it perfect? No - am I happy? yes its does minimise condensation and prevent mould growth.
Can I ask how many weeks did it take to feel the difference with the piv unit? I have mine a week and the attic smell it puts out is quite bad.
You keep saying that you are fighting the humidity from the outside but you are wrong. Please read this. The % humidity you are measuring is relative humidity (RH). Air can hold water, 100% RH means that the air holds the maximum possible amount of water. If any more water is present it forms droplets and falls. 50% RH means that the air contains half of the maximum amount of water it could hold. However, the air holds different amounts of water at different temperatures. For example, outdoor air with 85% RH at 8C and Indoor air with 40% RH at 20C both contain the same amount of water. If you let the outside air come into the house and warm up the RH will drop from 85% to 40%. This is a lower water content compared to what is already in the house. You are not fighting the outside humidity. Just let the air in!
If you consider limited to no heating at night plus poor insulation (such the room temperature is exceptionally close to the outside temp) then your statement may be untrue. I'm begining to conclude it's more efficient to NIV ie extract any moisture at source thus allowing the dew point to decrease, subsequently allowing the space to reduce temperature without condensation forming.
Compelled to disagree. Due to damp/condensation problems we have utilised humidity gadgets and a dehumidifier. We have noticed on very wet days on opening the windows humidity levels go up. Even went over 90 on one day. On a very good day in one room we hit 48. With the dehumidifier we have been below 45 but not comfortable very dry and uncomfortable sinuses. We are looking at PIV at the moment.
The ideal relative humidity during winter indoors is between 30-40% dry air is easier to heat but doesnt hold heat as well as damp air because of the thermal mass.
I didn't realise that!
I recommend you look into dew point temperature which describes absolute humidity. If it is very cold outside, (around 0 degrees C), then the air is going to be dry regardless of the relative humidity. In other words, cold air can't hold as much humidity as warm air. Relative humidity readings are just that, relative. Your indoor humidity shown at 6:28 seems high because your temperature is only 17.5 degrees C. Push it up to 20 and your relative humidity will probably dip below 60%. You'd be better off spending more on heating your house than spending money on running a dehumidifier to extract moisture from cold air (heating your house will reduce relative humidity and make it a bit more comfortable as a bonus).
On a rental property I own, the first tenant I had did not have an issue with mold for two years. After they left and new tenants moved in, within the first month they complained of mold. I don't know what they were doing differently, but I did ask them to open and close their windows more, and especially make sure window was open a bit when taking showers (the worst area of the property) but they claimed they were and it made no difference. After inspecting I realised they weren't exaggerating and the clean, recently decorated rooms now had mold in the corners and damp windows. I requested solutions from several different companies who suggested various things but mostly claimed the issue was due to poor insulation and created quotes for things like putting an extra layer of plasterboad along the walls for a crazy sum of money. I wasn't convinced but I was getting desperate as I didn't want the tenants to suffer with this.
Fortunately, just before I would have likely wasted a fortune on this, I spoke with a friend and they suggested a PIV. It wasn't cheap to get someone to fit it in the loft space (I paid about £1100) but once done, not only did it prevent more mold but within a matter of days all traces of existing mold were gone, it was unbelievable how well it worked (and is still working nearly 3 years later) and I'd recommend one in a heartbeat to others. There are other more cost effective and efficient solutions out there, but with most of them there is no certainty of if they will make much difference. After seeing what the PIV can do, I have confidence that it will definitely solve the problem, and that confidence is worth the extra cost if it saves putting people through more stress so I'd not hesitate to get another one fitted if I had issues in another property
Thank you for this excellent informative review. I wonder if you have experimented with the position of the heater unit? It would appear from your installtion video that it is unit mounted. Have you tried in the diffuser mounted method and checked what effect this has on the temperature of the cold air being discharged. Vent Axia have told me that the heater should increase the temperature by 5 degrees C. Be interested if you have any views on changing and evaluating the position of the heater unit.
It’s also related to how fast the fan is running. If it’s slower the air is heated more
My rational mind also agrees with your analysis, every technique comes at a cost, and as you rightly say what's as important is the efficiency (how much will any solution cost me, one off and ongoing). I have hideous humidity issues in a static caravan (well vented but regularly 90% in bedrooms during winter), with humidity outside at 85% - 95% so assuming no heating during the night and limited insulation, there's no point blasting air inward, so I'm thinking NIV ie extract moisture from source, the source being moisture expelled from the body. This will at least reduce the humidity to around levels outside and reduce the dew point, hoping for less due on the duvet, yes that's how bad it gets!
Thanks for your unclouded and honest report, i suspect many spend huge amounts on these systems and the more they spend, the 'better' it works (for them) 😂
We live in south west England (lots of misty/rainy days and an old solid granite building). We have always struggled to get the humidity in our house down below 70%, even with a dehumidifier running. I installed a Nuair PIV unit with the heating element before winter and was initially really impressed. The humidity dropped by between 10% - 15% in a few days and we didn't have to run the dehumidifier at all. Still got odd bits of condensation behind closed curtains overnight so it didn't completely get rid of that.
We initially noticed, like you, that the temperature in the upstairs hallway dropped significantly despite adjusting the temperature of the heating element. As the winter set in, the outside temperatures dropped to low single digits, and we had many successive wet drizzly days we noticed that the house just wasn't retaining heat very well at all. We also noticed at the same time the humidity increased a lot. We were running the heating a lot more than normal and the temperature in my toddler's room (very close to the PIV outlet) was dropping below 16 quite often.
I decided to turn the PIV unit off and straight away the heat retention in the house increased. The humidity in the house did rise a bit so we reverted to using the dehumidifier again. I think we will continue with this whilst the outside temperatures are so low and the outside humidity is so high. The dehumidifier actually has the opposite effect of the PIV in that it slightly warms the house too. Once the outside temps warm up I will turn the PIV unit back on and see what happens. I realise that the PIV system has other benefits in that it is changing the air in the house so in theory it will be fresher, and also possibly help if there are any Radon issues (common in this area of the country).
How do you turn of the Piv ?
@@amberc5147 I installed it myself so I fitted an isolator switch in our airing cupboard.
Did you change "heater threshold temperature" setting in the menu? by default its set to 5°C so thats could be why air temp coming in is the same as loft temp.
At 7.28 you mention the comment from your previous video about the hole in your ceiling, if you go back and look at 4.15 - 4.16 you will see it, it's got insulation stuffed in it though.
I have one fitted and i havnt noticed heating bills . But I'd take a little increase to solve condensation issues
Mine has been installed and running in my loft at 4pm today, its now 10pm and the downstairs air seems so much fresher. Humidity is also creeping down slowly.
Thank you for the in-depth review it was informative. I love that you put a bathroom fan in other rooms in the house - clever.
Thanks! I’ve connected it to a Tapo wireless plug so it’s now in a timer and comes on in the evenings when the fire is lit. Seems to be working well!
Got it installed by housing, after inspection, as we had lots of condensation , been on going for long time, and since the piv been fitted, it's costing like crazy, and can't turn it on or off? and now even colder than ever upstairs.
How do you set the heater unit to pump hotter not cool air in the settings, my girlfriend has the heater version and has lost the instruction manual? Thanks in advance for any advice!
Great review.
I'm not certain that a MVHR system will be suitable for a older and potentially drafty property, AFAIK the general functioning principal behind the MVHR systems is that it function best in a closed system (in this situation that means an airtight building envelope).
That said as with anything in the dampness/moisture housing sphere "in theory" and "in practice" may not necessary agree!
Thanks for the update sounds like it not for me.
Thank you
Just installed but wasn't sure if the settings to use
Really helpful hearing you're review of this. You mentioned previously speaking to people/professionals for their opinion. Can I ask who you would ask to come out (or to speak to) to see the property, to review what would be best ? PIV MVHR etc.
Hi, sorry for the slow reply. I used Envirovent.
@@lifeatleigh271 Thanks, I appreciate it!
Can the heating element be turned off? Not clear in the manual. Thank you
À Window left ajar simply cools the window on the inside and increases airflow over it, therefore reducing condensation. A sealed house with air circulation and a dehumidifier is the best option for me.
Fitted mine on Saturday (it’s now Thursday) and I went from several inches of condensation on upstairs bedroom windows to nothing overnight! I ran it on full beans 60L/min for the first 2 days and then put it back onto 3 bedroom mode and still no moisture.
So where did you fit it?
@@barnabybot it’s over the stairs on the landing. I didn’t have many places it could go really
All things considered....wouldn't it be better to install a couple of constant running (trickle) extractor fans and suck out the damp air??
I'm wondering if the impact ventilation routine can be automated by installing high output extractor fans in the kitchens and bathrooms that are timed to switch on for a few minutes twice a day
It might work, but I’d suggest turning the fan around to blast fresh air into the house, or one in one out so the air is pulled through the property. I believe the PIV works as it’s bringing fresh air in, not through pushing stagnant air out as advertised.
The idea here is that the higher pressure in the house prevents the outside air (at lower atmospheric pressure) from entering the house. Condensation tends to form on the windows because the cold outside air enters through apertures around the window and cools the surface of the glass casing the moisture in the air to condensate. With the PIV system installed the air movement is reversed (indoor air is forced out).
I'm using a diesel heater and it sounds like it does the exact same thing: it blows hot air inside the house...
Hi, I found this video as I’m researching these PIV units as a possible solution to mould in my partner’s property.
You raise some great points & new thoughts on the system, but I do also wonder if some of the findings are unfair or misunderstood.
The way my research has made me understand it, is that in addition to the warm air in the loft space being forced in, that air then moves around the warm air that gets trapped at the ceiling level.
Maybe, in order to keep a comfortable home, you need to increase the temperature by just a degree or 2? Not to compensate for the cooler air coming in, but to make the air it moves warmer?
One of the videos I watched, was from the University of Nottingham, and animation’s & explanations were quite detailed.
You shouldn't have warm air in your loft in Winter, if you have then your insulation isn't good enough and you're throwing money away by heating the loft.
I didn’t mention winter. I was generalising about the air movement. Regardless of the time of year, these systems are meant to move air, with air.
The warm air that is trapped at ceiling height, because of the super duper loft insulation 🙄, is stirred and redistributed by the flow of air from a PIV.
There will be a sweet spot balancing the heating, so the air the PIV is moving isn’t already cold.
If the building is kept on the edge of comfort, of course a PIV blowing outside air in is going to quickly decrease the temperature even more. But raising the temperature, just a couple of degrees, could make a big difference, and eliminate the need to boost the heating.
I wonder if a Air to Air Heat Pump (AC Unit) is a better solution, they say it works as a dehumidifier as well. In terms of efficiency, according to the technical info, it sounds good.
We have those, they only dehumidify on cooling. But work very well doing this in Summer. Winter is the issue though, but to heat and cool the house they are way better than radiator HP
I have the same unit in my 2 bedroom granit cottage in Cornwall it works a treat. I fitted and set the unit up myself., I have no gas just electric in my cottage my electricity bill is only £35 a month and thats a winter bill and that's not even with the £66 government grant I am saving that money 💪
How are you keeping warm?!
Chinese diesel heater pump to I get my log burner fitted very soon
Hi, can you tell me where you fitted the PIV vent? We have a 2 bed old stone cottage with a small extension (so living room and 1 bedroom at front, then a hallway with kitchen, bathroom and 2nd bedroom at the back). Not sure if fitting a PIV in the hall would work as it's close the backdoor which I'm thinking defeats the purpose?
You have many factors to reduce damp , you introduce airflow. Its as simple as that.The bacteria spores remain in certain areas due to not exacuating it. Also the lack of heat. So introducing heat is also required. Another issue could be water ingress into the property. Don't forget . When you introduce airflow you still need additional ventilation. Pull air in and pull air out in a circuit
Before even thinking of mvhr you will need a pressure testing in the dwelling first to get maximum heat recovery if this doesn’t qualify basically having fresh air in to each habitual room all the heat recovered 98% will be lost.
Hi Leigh, we have just installed the same one and wondered what setting you have it on, the instructions on this are so difficult to understand. It is quite warm in our loft at the moment and it seems to be pushing warm air out onto our landing…? Very strange and frustrating aargh !!
What settings do you have it on , have you worked it out as I'm in the same situation, fitting mine a few days ago.. any help will be much appreciated
Barrel fan on lowest setting is 1.6 watts.that about £5.00 per annum. Heater is 400 or 500 watts and only heats to 15 or either 20 degrees c model depending.. so anual cost about £130 per year plus £5.00 for powering fan total £135 aprox per year based on 27p per KWH..Heater cost is based on 6 months use.and taking into consideration the loft is at a static 16 degrees c.
At 10:45 your screen message talks about defrosting your Car Windscreen.. Purely by chance about 5 years ago I actually read my Car manual and it said to use the AC whilst blasting the screen.. It works surprisingly well.. Most people dont seem to do this..
I think this general conversation has too many variables to offer specific advice, but I would suggest getting professional advice (Ideally, NOT someone with a Product to sell..) to find the route cause of your problem.. Perhaps a SAP test.. Surveyor..
Opening windows has never worked for me unless you open another window and get a cross draft.
If the main reason for Mould is human/animal breath then just before you go to bed.. you remove the stale air (Electric Extractor fans) to outside for say 10mins and accept the lower temperature as you are going to bed anyway.. Mount the extractor/s high as hot air rises and that is the most moist air needing to be gone..
I find this is strangely leading to back to AC.. It is the poor cousin to Heat Pumps and never really took off in Residential UK because we seem to prefer wet Central Heating as opposed to ducted warm air.. High Energy prices are dictating our choices at the moment.. but who knows.. In a years time prices may plummet due to so many solar panels and wind farms..
Ventilation can be a complex science (fluid dynamics) and certainly has a lot of R&D surrounding it; this is key for newer properties, especially with their increased air tightness. But as you mention, there are plenty of people with a product to sell!
Unfortunately a lot of retrofit solutions can be inappropriate to resolve the issues effectively, resorting to either "negative pressure" (extractor fans) "positive pressure" (PIV) or more complicated balanced systems with heat recovery, air purification, dehumidification etc. It is probably necessary to choose/design a system to fit the property as there are a multitude of factors that will affect how well any system will work.
If you are a bit inventive, it can be possible to find parts from less expensive places, but an ideal system would be one that:
(1) Extracts stale air from kitchen & bathrooms (and possibly bedrooms/living areas) whenever the CO2 or humidity level rises above certain point (not continuous)
(2) Recycles the heat energy (or cool air) from the exhaust, through a heat exchanger and/or dehumidifier/heat pump
(3) Inputs clean (filtered), warm (or cool) air to the points that need it.
(4) Gently moves air around the house to help reduce the possibility of stagnant air build up. (Think of the air in a house like water in a fish tank!)
It is very inefficient to just extract the warm, damp air from kitchen and bathroom to just exhaust it outside, because this will invariably be replaced with cold air leaking in from other points in an uncontrolled manner.
Equally, it isn't perfect to introduce higher pressure air (PIV) at a constant level without considering where the exhaust air is escaping (again this could be losing energy). The single point of input can be effective because this allows more control over what is being allowed into the house, but if this can be balanced against extract points, cycled at different times it would create more of a flow and introduce air throughout the house.
The majority of people have very little interest in understanding and spending time managing a ventilation system, so most products are understandably designed to operate in the background with minimal input, but if you don't mind some occasional maintenance and adjustment it can make a huge difference to air quality!
Ive had the same PIV in my home for 2 years now (unheated) before we installed it we constantly had condensation all over our windows. Within a week of it on 2 bed setting the condensation was reduced to half the height of the window. So i turned it up to the 5 bed setting and ever since we've had no condensation on our windows.
Im no scientists and i can't say if it works as the makers say but it works for the purpose that i bought it and thats good enough for me.
On a side note yes the hall way the vent can get fairly cold in the winter i have just fitted a heater unit so will see how it goes.
The idea that someone put forward about using a timer so that its not on in the evening sound like a good one to me so i may try that out.
Turned mine off making house colder and doesn't stop condensation
Maybe just having a ceiling fan in the room that suffers from mould or damp to circulate the air?
You're in your loft space? I have a dorma bungalow and I'm struggling to understand the best location I could have for this sort of system, I'm wondering if you could help?
Hi, I would recommend one or two of these - amzn.to/3Xsa0Df
Did you get the HRV?
Was wondering where the water goes as the dehumidifier collects water which you have to empty into sink nodody mentioned about water
It’s not a dehumidifier, so it doesn’t collect water. The manufacturers suggest that the water is pushed out of nooks and crannies, which I find harder to believe. As I said in the video, I think damp issues are resolved by fresh air being circulated.
I've just ordered one of these systems, I'm very much hoping it will alleviate condensation and mould issues we have been suffering recently.
A note about humidity % values - this is "relative humidity" (RH), which means the quantity of moisture contained in the air *relative* to the maximum it can possibly retain. The maximum amount it can contain is temperature dependent, so although the outside air might have 95% RH the actual gross amount of moisture entrained in that air will be quite small when the outdoor temperature is cold. When that air is heated (after entering your house) the maximum moisture retention capacity increases significantly, whilst the gross quantity of moisture hasn't changed. The RH therefore comes down from 95% (at cold, outdoor temperatures) to around 40-60% at indoor room temperature. Obviously we then add more moisture to the indoor air by cooking, breathing, showering, drying clothes, houseplants etc and we have to get rid of that excess moisture somehow (extractors, PIV, open windows etc).
You're absolutely right about good ventilation coming at a cost - one way or another we're always fighting cold outdoor temperatures. However, you're not fighting moisture from outdoors as much as you think.
Thanks Matthew, that's a really interesting point that I hadn't considered. I hope the system works well for you!
@@lifeatleigh271 3 days in and it has eradicated condensation in the bathroom, main bedroom and office room, which were all badly affected before. My son's room still has a little condensation on the window in the morning but that's due to a blackout curtain that attaches to the window with suction cups. The upstairs landing is cold and has a faint whiff of "loft smell", prices I'm more than willing to pay for resolving the damp/mould issues that have plagued us every winter for years.
Good explanation of Relative Humidity. I use google to find online Absolute Humidity Calculators to work out how many grams of water per cubic meter which I find more useful than RH.
@@garytango I don't know why we insist on reporting humidity as RH; it's useless as a basis for comparison. 100% RH in Siberia contains virtually no moisture, 100% RH in the Amazon contains a shitload of moisture. Same value, vastly different moisture levels. Why we can't just report it as an absolute quantity in g/m3 is beyond me, we'd soon get used to how many g/m3 is normal, dry, humid, extremely humid etc, in the same way as we're all familiar with degrees C/F for temperature.
@@matthewhook3375 I imagine reporting in RH is used because it allows determination/usage of the associated dewpoint temperature
Great video! A system with a built in dehumidifier and air purifier would be ideal here in the UK houses but that would be even more expensive to run.
Ive retro fitted mvhr into a concrete flat heated electrically, its fantastic but parts and labour are high! I fitted it myself and had to do a lot of coredrilling, sdsing, and boxing in. Also, even with soundproofing around unit and in line silencers, you can hear it in every room. Its a low fairly innocuous noise but it is there. When you have a shower or it senses high moisture (you set the parameters) it ramps up then it is very noticable for 15 or 20 minutes usually. Sometime on humid days it just stay on as it cant achieve its desired humidity. Ill just turn it off on those days. Blauberg said it should still be able to maintain a lower humidity than oudoors and stay on low but mine doesnt
Its good! But i always wonder if a flat master would have been a lot less time and money even with the heatloss.
I'm having mine took out next week, far too cold for me. Does anyone know what would happen if a neighbour had a garden fire?
What about trickle vents?
I am currently in the market for a PIV unit. I have been unable to adequately heat my home since the start of the energy crisis amid financial concerns, which has caused substantial damp issues (on top of a pre-existing minor issue). So reviews from those currently using this system are of great interest to me. This is in no way a criticism, merely observations after watching your video, that make me question some aspects.
You say that the air being pushed through your ceiling when it is 10 degrees outside is 14 degrees (loft temperature), which is 3.5 degrees lower than the temperature you desire. You later say that you may as well not have one of these and instead open your windows. If you find the 3.5 degrees a significant problem, then you surely do not want those windows open when the outside temperature is 10 degrees as this would be a much more significant drop in temperature.
I think that you have not considered the fact that in many instances, it is neither practical nor safe to leave windows open a lot of the time, regardless of the outside temperature, and this, in many cases, is why properties develop condensation and mold issues in the first place.
Regardless of the science, it is clear that this system works and I feel that for many, it is a much more efficient and warmer way of solving the issue than placing fans throughout the property if this does in fact do the same thing, and is a safer and more practical solution than leaving windows open if like me, you live in an area where an open window will invite unwanted attention.
I guess ultimately it comes down to personal circumstances. I did enjoy your review though and will be looking to also watch your first review of the system.
Hi Jon, thanks for your feedback. Maybe I wasn’t clear, the concept of leaving your windows open is a temporary thing to flush the stagnant air out, so you leave all the windows open for a couple of minutes twice a day. The outside temperature is colder than the loft temperature, but, my thoughts are you will find it less of an impact than the PIV. After the hot stagnant air is flushed out, your central heating system has to heat your house up again a few degrees once, with the PIV it will be fighting the cooler temperatures all day. If you can’t open your windows through the house for a couple of minutes each day due to your location then maybe a PIV would be the only option, but if you can, then I’d personally highly recommend saving your money rather than wasting it on a PIV. I hope that helps!
@@lifeatleigh271 thank you for getting back to me. Unfortunately, the windows open for a short spell each day has been tried and failed in my property, the condensation issue is so bad on some mornings that there simply isn't enough time with windows open to dispel it all and we end up with a very cold home in the evening as they would then be left open for up to an hour to clear it. We also have the little salt pot thingies on window sills to help remove the moisture which does work to a small degree. It has only gotten to this level since the energy crisis as we could not afford the bills so I still think a PIV is the answer. I don't fully understand (or buy) all of the science behind it but to me, it seems the most cost-effective and practical solution currently available. I am hopeful that it does as good a job for us as it has for you.
Try opening windows at night when heating is on for a couple of mins and make sure that they are all open at same time so you get cross winds that will shift humid air out….you should see a big difference with condensation in morning.
And before you say your letting all the hot air escape yes this is the same as what the PIV those 24hrs a day but doesn’t use electricity. if Done quickly (even 1 min) a few times a day when heating on it will make a difference but I stress you need the cross winds by opening windows front and back at same time.
If the house is less humid it will heat quicker and heating won’t need to be on as long. E.g when humidity was 80% in my house it took 1 hour of the heating on to increase temp by 1 degree. Now humidity down to 45% it heats in 25 mins
Thank you for the update - I am hoping to have a rival system installed on Monday as we have terrible condensation, and mould growth in the extremities of our property. If it will cure this problem, and I don't have to move furniture around every two weeks to treat surfaces with a strong mould spray, then it will be a success for us.
Best of luck with it, I hope it works for you!
Problems around the outside of the property could be associated with blocked drains and raised ground levels. Even something as simple as blocked or leaking gutters, cracked concrete around rain water collecting drains. If the ground and walls outside look constantly damp there is an issue. Don't get sucked into rising damp treatments it's very rarely relevant.
The basics are making sure all drains are sound and ground levels correct. If water is carried away from the house as it should, then the walls can't get wet (rain should dry quickly, in a few hours if everything is as it should be).
@@lifeatleigh271just a follow up, the piv unit installed in our home has worked wonders. It was installed 16/01, I cleared any surfaces of residual black mould 2 weeks after instal. Since then, we have had no more mould growth in the areas of the property that were most susceptible.
Granted, the property has been colder (particularly given the expense of central heating) but we have survived. Hopefully energy costs will be less next winter so we can afford to have the heating on a little more to offset the cold air being brought in by the piv.
Overall I'm very pleased with the unit, and definitely think it has improved internal air quality. Hydogmeters registered 75%+ before install, 60-65% since instal
@@mikedaniels8628 that’s great that it’s working for you! Like you say, they are great except for the cold air and cost of heating. Since the video I’ve changed ours so it’s set to max ventilation, but on a timer for 12 hours set to work during the day when the most condensation is being produced. This far it’s working well and will hopefully help our bills!
@@lifeatleigh271 The amount of damp air produced is dependent on what you're doing and in which room, it isn't completely higher during the day at all. Our bedroom is highest at night, but lowest during the day because we aren't in it during daytime. All rooms have high periods and low periods depending on what is happening in them at what time (and many other external factors).
Have you had a chance now to check the costs of your electricity bill when running with the heating element on?
I had a piv installed in January. It doesn't even register on the smart meter that it is running ... I've seen no increase in the running costs (as someone who keeps a very close eye on the smart meter).
I cannot speak for the heated version however
400w x 24hrs is 9.6kwh x £0.38 is £3.65 to run the element heater a day. It does nothing either in reality...best to run this along with a HP Air to Air and get 40kw of heat in the house over 24hrs for the same money.
Can I just check? Originally you did say that you still had condensation, has this now changed with use ? Thanks.
Hi Chris, I'd say there's a reduction of 80-90%, but we've also had the fire going a lot more than usual.
@@lifeatleigh271 Thank you for that, we moved to this damp cave 12 months ago, but at least it's a very quiet, damp cave,,Chris.
Did you try dehumidifiers before the unit.
Yes we did, all winter!
I have just installed one and also noticed the cold temperature of the air coming in although I set the heater to 18. Has anyone noticed the air having the chill taken off it or not? Or have I set the settings wrong?
it's a 400w heater and will eat your electric bill if left on all day/night (£3 to £4 a day) You could run an HP Air to Air and heat the whole house for that much electric.
Our property doesn't have a condensation problem (probably due to being quite drafty) but rather really poor circulation resulting in stale stagnant air and a musty smell. Since you say the PIV doesn't expel damp air but rather circulates it I wonder if it would solve our problem
Hi, it would really depend on the air being drawn in, if the air is good, then absolutely yes. Now the summer is here the smell of the attic has become more pronounced again, so you might be swapping one smell for another. As I mentioned in a previous comment, I have now put it on a timer so that it comes on at specific points in the day. In winter I set it to come on during the day, but in summer it’s better coming on at night. When the attic reaches above 23 degrees (I think) the PIV cuts out to prevent hot air being blasted in to the house, this temp cut off can be adjusted in the PIV settings. Certainly worth a go if you have a well ventilated roof void. My only final thought is if your house is quite draughty, then would the smell be from stagnant air? Good luck!
@@lifeatleigh271 Thanks for reply. I hadn't heared of the 'attic smell' returning after the first few weeks, but makes sense in hot weather. Your solution seems logical. Regarding draughts - it is not that our house has a hurricane flowing through, more you can feel slight draughts at some of our old timber double glazing (which is being replaced). But, I take your point, we could have a leak or something. I do think the design of the house is not great and does not allow any air flow - mainly in the large hall that has no natural light and acts as a barrier between the front and rear doors
At 10.37 you talk about blowing air in a car. Onto a moist windscreen. Asserting it will eventually dissipate purely as a consequence of air circulation. I feel you've missed the reality. The moisture settles out of the air onto the windscreen and other surfaces because the temperature of the windscreen is colder than the air adjacent. It will only 'dissipate' eventually if the windscreen warms up and/or the air warms up and is able to re-absorb the moisture.
Thanks for your video. we were considering this system, but was not sure about it. After watching this I think we'll pass.
What was it that made you want to pass ?
If it's pulling fresh outside air into the property, but you say it isn't pushing the damp air out, where is that damp air going? Is the air pressure in your house increasing constantly until it's unbearable? It's got to be exiting somewhere.
The point I’m trying to make is how do you know it’s pushing the damp air out and not the warm dry air, or the fresh air that it’s bringing in. It can’t specifically target the damp air, it will just take the path of least resistance.
Basically you may as well just open a couple of windows a little bit for around 15 minutes to get air circulation, that's all that happens with the ceiling vent
It does have the benifit of push8ng out air around windows which is white condensation tends to be an issue. Also with the house at a slightly higher pressure, all leakpoints are leaking on same pressure gradient rather than one window open agar
Has any body worked out the cost of running a PIV unit
PIV draws in outdoor winter air, which has a much lower moisture content than warm indoor air. As the pressure increases, warm damp air exits through wall, window and other gaps & cracks.
Heat will be lost in exchange for dehumidification. It's a viable solution if you switch it off when the house has reached a suitable humidity.
I wonder if you insulated the roof void and had minimal insulation above the ceilings, whether that would create a more comfortable environment. You are having to heat the incoming air anyway so if you could do it before it enters the fan it might be beneficial. You would need to have good control over the roof space ventilation to avoid losses though.
You could do and I'm sure it would help, but it would be quite an expensive process!
@@lifeatleigh271 Perhaps a better solution would be to have a small, say 3 feet by 3 feet, by 4 feet high, insulated box structure in the loft to house the unit, then provide air intakes at the bottom sides of the box, remove the insulation from under the box so the rising air heats the inside of the box, and in doing so, heats the incoming air, would it work?
@@Gavin_GbkThis is exactly what I wanted to do. Keeps the air warmer around the PIV but the attic as whole still has the appropriate ventilation
You would just be recirculating the hot humid air and it would remove the benefit of the PIV unit. You need fresh air this is why it only works in a well ventilated attic
Will these be ok for a home that is air tight and poor indoor air quality,,,to suply fresh air in the home?
Yes they would, however, I would check the ones with heat recovery like in the link in the description. Good luck!
@@lifeatleigh271 Hi .
But would the attick or loft air not be horrible coming in to the home,,Attick air normaly smells bad would it not efeect your chest or lungs???
@@makkavelli3972 the attic has to be the ventilated type, if it’s not then you would have to either ventilate it or use a different system. If it is ventilated then the smell of the attic disappears after a few days. Heat recovery units draw air from the outside, so they are advantageous to these units.
So it's just £3 fan for £400?
House with usually high humidity is down to the house sweating. For example if you have a external render on a lime mortar then most likely the house can not breath
I wonder if a Diesel Heater is actually a system that would work better in this case. It blows warm fresh air in the house and the stale air could get out via nooks and crannies. It's cheap to run and from what I hear in this video, these heaters sound like they do exactly the same thing as a PIV-system...
Of course, they don't look as professional!!
Where your heat is? In the air, in the humidity and in your walls. Cold air holds less humidity. I would replace the humid air in your house and afterwards heat your house.
Excellent info, thank you. My daughter is getting one for £1400 but I don't believe they work.
1400 quid ? Really ? Yes I know this is 7 month old (your comment) did it work ?
@@stequality I've totally forgot to ask her but I will and let ya know.
@@steveedwards4495 I have one but doesn't get rid of condensation, probs settings ain't good enough, just makes my landing a bit colder it seems
I think I would rather go with a Heat Recovery Ventilator or two....
Headlines, we don't have mould, we don't have condensation. Yet you question it? Surely you need to set it to the lowest setting, it should not be blasting air in. Give it a go on the lowest setting.
My ******* landlord put one in my room. Currently, I'm watching this video in a temperature of 9 °C. The room is still very humid, but it is now too cold to run my dehumidifier. When will we end the evil that is buy to let?
You shouldn't fit a MHRV system with a log burner...it isn't recommended, if the is an imbalance in the input/output you risk pulling fumes onto the house from the stove.
I agree with you. No difference to opening a window. Folk think it's doing a really good job but have they left a window open 24/7 before installing a piv? Or just leave your loft hatch open. It will do the same thing. Cold air falls then gets replaced by air coming in from outside. Also, nearly £400 for a low watt fan and some ducting? Ludicrous.
Some of your comments just don’t add up scientifically. It you say “pumping air in” then air must be escaping from the property somewhere, otherwise the fan would soon become unable to move any further air into the property due to pressure build up. The amount of air escaping from your property will be almost equal to the amount of air your fan can deliver. The amount of ‘positive’ air pressure developed in the property will be very small but is enough to move air out of your building. With respect, I don’t think your statements can be supported by science.
I think you’ve misunderstood my statements! I haven’t said air doesn’t escape, it’s patently obvious that air will escape!
Then if air escapes and not simply circulated (moved around) as you suggest in your vid, what makes you ‘disbelieve’ the claim on how it works?
@@maxh9761 the claim is that damp air is forced out, what I’m trying to say (maybe badly) is that damp air alone cannot specifically be targeted and pushed out. If the PIV is placed next to an open window then the air from the PIV would be the first to exit. Damp air alone cannot be targeted, yes air will escape, but that’s just air in general. My point is that I believe it’s the movement of air circulating that prevents mould build up. Think about a misty car windscreen when you blast air at it. Even without the AC on or heating, the moisture will eventually be removed and the car doesn’t explode from the positive input from the fans, bonus.
Ok but I think that a considerable factor is that air is ‘forced’ out and fresh air is drawn in. The water content of the air will tend to diffuse and even out the overall humidity of the internal air. So long as the outside air has a lower humidity than inside, there should be a net lowering of the internal humidity. The other effect is, as you say, a movement of air is being encouraged at every point that air is able to be expelled, which is something that would be difficult to achieve in any other means.
Piv is a fantastic solution but ultimately having a desperate trickle vent is the Jack to the Jill and completes the science
you pay for what you get - A proper mini air Handling unit, with treated fresh air in, and exhausted air out - money talks I'm afraid?
I've stopped watching as soon as you have tried to pass your views on the cons and not actually having a clue if you are talking fact.
It's cleared your damp and condensation.
To reduce condensation; reduce the temperature of surfaces and or reduce the level of humidity. All this does is take warm air that may have more humidity due to breathing cooking drying clothes etc from inside the house and swap it for cold air which is slightly lower humidity from outside. Pointless really.
Zzz😴😴😴
Fook me i now feel depressed listening to the bloke,
Good God.......i`m literally SHOUTING at my screen........`Cooooooooomme Onnnnnn`..........How to make a 5 minute post into 20 minutes.......Sorry mate, `posts` aren`t your `thing`........!!........From the `jumps`, it looks like you`ve edited it down as well........lol..........Maybe `storyboard` it prior to filming, just to eliminate your rambling........
Sorry nearly fell asleep monotonous presentation zzzzzz