How effective are DVS and similar systems? Feedback welcome!
Direct ventilation systems (such as those marketed under the brand names DVS and HRV) consist of a fan mounted in the attic which forces dry filtered air from the attic space through a system of ducts into the living areas of the house. The creates positive air pressure which forces moisture-laden air out through gaps in the building envelope.
The DVS brand has been appraised by BRANZ as offering a solution to reducing condensation and improving ventilation, in buildings where no specific building code requirements exist for mechanical ventilation. However recent research from Otago University* has cast doubts on whether these products can deliver on some of their other claims such as providing “free heat” from the roof space, especially in winter.
We are interested in feedback from anyone who has a mechanical ventilation system installed. Where do you live, what brand have you installed and what has been your experience of how it has performed? Would you recommend the product to others?
* I J Smith, B R Carson and M R Bassett. Is there free heat in the roof spaces of New Zealand houses? Mechanical ventilation systems and heat transfer .Department of Physics, University of Otago, PO Box 56, Dunedin, New Zealand
May 15th, 2009 at 3:22 am
Hi, I had an HRV system installed over 3 years ago. I do not believe it can perform as claimed. In the summer the roof temp can reach 45°C and does not cool until late at night, and then the unit is quite noisy and so I turn it off so I can sleep. In the winter the opposite is true - the roof temp rarely exceeds the house and so you cannot possibly heat anything. The whole thing is on an 8 hour cycle, so even if you turn it off it will come back on again 8 hours later. I deferred the filter change last time because I keep it turned off when I am at home but they did come and change the filter earlier this year. I spoke to them about the noise and they agreed - it was too noisy and said someone would be in contact with me re that. I am still waiting. They also suggested, if I had better insulation in the ceiling the noise would be less. What a pity they did not take that into consideration when selling me the product. I explained about the heat/cooling issue and was advised if I installed a summer kit and another fan and another computer key pad I would notice a difference. The summer kit would draw air from the “cool” southern side of the house and help cool the roof air so you could inturn cool the house. Sounds logical but I am not prepared to spend another $2500 to find out. I am not convinced . I live in Auckland and can only ever sleep for 8 hours because my HRV thing comes on and wakes me up. For my house - hot in the summer and fridge like in the winter - it is not terribly effective. Thanks
July 1st, 2009 at 11:10 am
I have had a DVS system installed in my own home and in a rental property. My own home is brick with batts in the ceiling and a large gas heater in the lounge, wooden windows. I had extra vents installed in the four bedrooms. I have noticed a big difference in air quality, (the house does not have good air flow) and the bedrooms are much warmer in the winter. The system is quiet- no noise at all and no draughts. It cost about $2500 a couple of years ago. Each year a new filter is needed. It costs about $50 if you change the filter yourself but the company will come and do it for you for about $150.
The biggest changes were seen in the rental property. This is a 3 bed fribolite house built in the 1970’s, aluminum windows. It was extremely cold as the tenant does not use the installed flued gas heater. It was damp and the bedroom on the ‘not sunny side’ had mould in the wardrobe and on the ceiling. The windows ‘cried’ a lot and in the winter it was like walking into a freezer. When the DVS was installed - one vent in lounge and one in each of the bedrooms, the supplier said it would take about 4 months to dry the house out, and about three weeks for the mould to die. They were right. After three-four weeks I just cleaned the ceiling and it looked like I had just painted it. There is no mould anywhere in the house now. The tenant still does not use the heating but the house is now much warmer. I would definitely recommend a DVS. I do need to turn it down in the winter nights. I found the agent excellent and honest- he did not recommend the heating component- said the gas heater was better.
I am interested in trying the airfoam installation, but note the energywise site does not recommend this. Any one have comments on airfoam?
PS I live in the Manawatu
August 28th, 2009 at 7:49 am
I have a DVS, installed at least 5 years ago by a previous owner. My little faith in such systems has been blown away by experiencing our small DVS myself. Even though there are only 2 vents in our 3 bedroom home it works ! In fact, it even works when it is not turned on because early this winter I had it turned off (my initial lack of faith) and our windows were a little wet each morning but when I blocked the 2 vents with towels for a couple of days because of letting off insect bombs in our attic (I mistakingly thought the fumes could come into our home through the vents) we then had pools of water on the sills off the very wet windows because of the towels blocking the vents. Just having the vents had been making a difference. Impressed, I removed the towels and turned on the DVS, leaving it on the bottom/low setting, and wow, our windows have been always dry throughout this winter. As for heat transfer, on a sunny day the system does warm up the house, (we moved here last summer and found the house too hot for comfort until autumn arrived and now I know why), but for winter days with no sun another source of heating is necessary. We live in Orewa and I now whole heartedly recommend DVS for a dryer, more comfortable home.
March 2nd, 2010 at 8:21 am
Had a MoistureMaster system installed 2 years ago so we have now done 2 winters with the system. It did what we wanted it to - reduced the condensation to nearly nothing, put clean, fresh healthy air in to our home and our children have benefited - son went from using a preventer to nothing and has had no asthma episodes - could have grown out of it but I think the system has definitely helped. And, LOVE a dry home.
BUT, the negatives - absolutely freezing in winter and because the installation didn’t go according to plan the fan is very very noisy - drives me spare. But, we have contacted MoistureMaster and they are going to rectify the problem - move the fan, review vents and install the inline Heater. We have worked out, based on MM literature, that we should be able to achieve an ambient temperature of 12-14 degrees in winter by having the heater running on low/med for no more than 12 hours a day. Cost should be around $30 per month. I think alot of the problem is that people think DVS, MM, HRV are Heating Systems and they are not. Eliminating condensation in NZ buildings that are not designed to eliminate condensation is there only aim. You HAVE TO have an additional heating source to get the system to run efficiently. If you don’t you will probably freeze and the condensation reduction won’t be that good. We are very nervous about the additional $750 for the heater - alot of money with two young toddlers and one income. We just hope that because we are in Auckland we won’t need additional heating once tucked up cosy in bed at night. But we are prepared to have to instal at some stage a heat pump in our main living area. Fingers crossed for a good result - certainly reviews on these systems are all over the place and there is an awful lot of misinformation and little understanding about how condensation is caused, and reduced.
March 7th, 2010 at 10:10 pm
Not at all sure this is a good idea! I have heard of some cases where the in line heaters have added a LOT of money to the power bills (we are talking $100 or more per month).
If the outcome is a house with a comfortable temperature and reduced humidity, what you will be wanting to do is to heat the existing and incoming air up to a temp that is comfortable with at the lowest cost and least hassle.
Peg back the airflow (if possible) to a level that balances with the existing heating – you will need to watch the humidity, and keep moisture sources under control ( use extractor fans in bathroom and kitchen, vent the drier to the outside, oput kids on pots when cooking , have security stays on some windows to get a sm,all cross draught during the day, etc).
During winter the external air has a much lower absolute humidity (cos it’s cold) so when it comes inside and is heated then it’s relative humidity is pretty low, so maybe you dont need such a high airflow from your DVS in winter.
Get an efficient heater or woodburner to replace that heating - 7c/kWh versus 22c/kWh for an inline heater.
You could also look at using a dehumidifiers instead of the moisture master. They heat and dehumidify. They give out more kW in heat than is used (due to the latent heat of condensation) and 98% of the other elec eventually turns into heat (apart from the hummm and flickering lights).
March 22nd, 2010 at 3:18 am
Heather. Don’t add a heater to your MM. They suck up the power. Better to use a heater in the rrom oyur in and heat the dry air in that room. Heaters in the roof are a waste of money.
A ventilation system is not a heater but can add heat depending on house and roof etc. I saved $700 a winter in the south island with one just from free roof heat but not everyone can do this.
There is a new coy with an HRV clone thats much cheaper called SAYR or something like that. They said they can do an HRV filter at $80 rather than $200 and we all know the big companies make a fortune.
There controller looks real smart. In the end airflow and price are the key.
April 22nd, 2010 at 7:51 am
Wonderful comments. I have a HRV and filter needs replacing every two years, have been charged over $225.00 to replace. Where would we buy the new filter in the Auckland area?
April 22nd, 2010 at 9:41 am
I lived in two houses with DVS, the systems control were terrible, it would turn the fan off if the roof space became too hot but not if it was too cold. it blew cold air into the houses all day and all night. Only very occasionally did they provide warmth. I checked the quality of the air coming out of the vent on several occasions with a meter and the air contained more moisture than was in the house already. It may have made a small difference to the beading of water on the inside of the windows but that is no indication of it working as you need a temperature differential between inside and outside for the condensation to occur, the house was like a fridge when it was turned on. Ventilation is extremely important however I don’t think that DVS or HRT are very good systems although they are getting better by having heat exchangers and feeding fresh air form outside not the roof space. It amazes me that these system don’t measure humidity and rely on temperature for control and have flawed control logic.
May 3rd, 2010 at 5:01 am
John, you must have a weird roofspace. My experience is totally the opposite although it wasn’t a DVS. I do know they have less airflow and therefore need to be on more. One comment you made is correct, the systems controller is the most important component. If it’s not clever enough, it will dribble air in when it’s able to warm and then because the house doesn’t rise in temperature fast enough you will get cold air when you don’t want it. My HRV seemed to do it correctly.
To cover the humidity angle, they don’t need to measure it. It’s common knowledge that as air expands the moisture content stays the same which means when the roof temp rises the humidity level must be lower per cubic meter of air. Its a law of science. Thats why my experience was good, it came on when the temp rose as the controller was intelligent. But SAYR’s little touch screen one looks really good and it measures outside temperature as well it seems.
May 3rd, 2010 at 10:38 am
I am surprised at some of the negativity towards PPV systems. We have had 2 now. The first was an hrv. We were very impressed with results. We moved and put in a SAYR PPVS and like the hrv, the results are amazing considering what it simply is.
We have friends with dvs and it would appear the main difference between our SAYR and the dvs is the fan output and the ’smart’ controller (as David said above). If you dont have a powerful enough fan and a smart enough controller then you are at a huge disadvantage and in some instances it can work against you.
Today was a cold dank day and the sun was struggling to get through. Winter is peeking around the corner, it was 14 degrees outside and yet we had 21 deg inside, the air was dry and had fresh smell, it was mid day. It is now 10.30pm, it is 11deg outside and yet it is 20deg inside. We have used no other heating source. Our house is nothing special. It is a 1966 wooden house with no insulation in the walls and has very old batts in the ceiling.
We will never live in another house without a PPV system.
May 3rd, 2010 at 9:33 pm
Just a quick note following on from above.
This morning at 7.30am it was 14 deg outside, a bit warmer than yesterday. It was only 15 in the ceiling and inside was 18 deg. No heating. When I left home at 8.30 it was still 14 outside. Inside was still 18 deg. Temp in the ceiling was 17.5 deg. I know by now (9.30am) the temp in the ceiling will be over the inside temp of 18 and the system will be operating at 100% and warming our home with fresh dry warmer air. We have ours set at 22deg inside so when that inside temp is reached the system will reduce down to filtering mode. It will no longer warm the house but will still introduce fresh dry air. Wow. A great system. Who would not want one. Thank you SAYR ventilation.
May 12th, 2010 at 3:10 am
Tina, apparently you need to contact the appropriate HRV representative directly to purchase a new filter. There are franchises in New Lynn, Grafton, and Manukau. http://www.hrv.co.nz/about-us/franchises.aspx
May 12th, 2010 at 11:55 am
Tina and Susie.
You can get filters for HRV and DVS from a company called Filter Corp. They are about $90 and you can DIY. It is very easy to change these filters.
http://www.filtercorp.co.nz/home_ventilation.html
May 28th, 2010 at 2:26 am
We have a Moisture Master with the heater included and it is amazing! Why would anyone put a system in without the heater? It will blow cold air in all winter. The heater takes the chill off and we do need a bit of extra heating to supplement it in the middle of winter, but our power bills have dramatically decreased as warm air is easier and faster to heat.. We have no roof cavity and MM were the only company who suggested we put the unit under the house with the vent outside. We approached 4 different companies and they were useless!! The salesman have no idea what they are promoting and it is false advertising. The difference is nothing short of miraculous for us and I recommend it thoroughly.
June 1st, 2010 at 1:18 am
@ Barb.
I’m glad you’re happy with your DVS system. However, I have to question your logic. The DVS (and other PPV system) is designed to work through positive pressure, forcing roof air down through the ceiling vents and pushing the internal moist air out through any available air gaps or vents.
If you have the DVS turned off, things will actually work in reverse. Due to the passive stack effect, warmer inside air will rise, going up through the DVS ceiling vents. While this isn’t what they’re designed for, it will still provide a level of ventilation for the living areas, and I suspect this is what you experienced. If you then block off these vents, you block off this natural ventilation path, hence the increase in condensation in your home.
Matt.
June 1st, 2010 at 9:23 am
Janine, your braver than me to take air from under your house, especially with only a MM filter, and then pump that in whether warmed or not. I would definitely get the air tested a.s.a.p. from a recognised company who do independent tests. Your health could depend on it.
June 8th, 2010 at 2:17 am
I’m trying to weigh up which is better for my house. A ventilation system or a heat pump. Our house is an old single level 3 bedroom house with an uninsulated lean-to extention attached to the main living area. My son and I are allergy sufferers and asthmatic’s. The house is built almost directly on the clay which means no under floor insulation.
Our house is damp and cold. There is constant condensation on the window during this time of the year. We ‘do’ have good insulation in or roof but this is comprimised by the lean-to not having any.
Any advice would be welcome. Cheers
June 9th, 2010 at 2:55 am
We live in the manawatu and had a DVS fitted into our original house (1960’s) in 2003 because our windows streamed water and we had a major mould problem in one of the bedrooms. We also had a gas fire at the time which we removed and replaced with a woodburner (because we knew that the gas fire was a major problem with condensation creation. The walls in the house actually felt wet! The DVS chap set us up with a set-up with one, yes just one outlet positioned in the hallway and due to us having it fitted at the beginning of winter he increased the money back guarantee if it didn’t sort the condensation out from 3 months to a year. You can believe this or not but the condensation was virtually gone within 3 weeks of starting the system up. The only down side from the system was the freezing cold air that gave you a serious wake up call every morning when coming out of the bedrooms!
I need a system to go in our new house now (a pre 1900 villa) so am open to peoples suggestions on whos systems are the best.
That is any one except HRV. - I hate pushy salesmen who try to treat me like some sort of idiot which seems to be the way they work. Plus of course anyone who thinks they can cook sausages on a roof while sitting on it in only their shorts has got to be pretty dumb
June 9th, 2010 at 3:11 am
Hey Jamie,
I’m an ex-builder and to be honest with you all three parts are as important as eachother. There is no point thowing money at a heatpump if you are going to lose a load of your heat straight out of the walls (they are not as cheap to run as the salesmen would have you believe although they are cheaper than many other forms of heating!)
Damp air is extremely hard to warm up so if your house is damp, again it’s a waste of money to buy the heat pump.
If money allows I would get the walls insulated at the same time as having the ventilation system put in. If not put the ventilation system in first. The most important thing to understand is that each of these three parts will not work efficiently without the others.
Just be warned some of the salesmen/companies will tell you anything to sell you their product. Ventilation systems DO NOT HEAT except when you don’t actually need it. If they tell you it does more than helps condensation and, possibly, allergies make them prove their statement. I would be very suprised if they can (they will try to baffle you with lots of figures). If they get nervous or agitated when they have to explain it means they either don’t know or they are trying to pull a fast one.
Hope this helps
June 9th, 2010 at 7:05 am
Jamie
The first thing you need to do is to decide what are the main things you are wanting to achieve.
Do you just want to warm your home?
Do you want a drier home, which is easier to heat.
Do you want to reduce moisture?
Do you want to reduce pollutants, dust, pollens?
Is there people in the home with allergies, athsma etc?
There are really only 2 options.
1. Heat Pumps.
2. PPVS - Positive Pressure Ventilation Systems.
Lets quickly look at some pros and cons.
1. Heat Pumps.
pros: Very effective method to heat your home. Relatively cost effective, say basic heat pump at $2500.
To run a 6kw heat pump will cost the same as running a 2kw fan heater.
Cons: Does not dry or dehumidify your home in winter. They only dehumidify on cooling mode which is not ideal in winter. Even though they are an effective and efficient heater, still the cost of running a 2kw heater over a 24 hour period would still add up for a month. It is rare for a single unit to heat a whole home so you may need 2 if you don’t want the bedrooms to be 10 deg cooler than the living area in winter. Can be noisy and unsightly.
2. PPVS
pros: Very good method of ventilating your home. Can drastically reduce the moisture in a whole home. The air is filtered reducing pollutants, pollens, dust, allergens, bacterias. A drier home is easier to warm and stays warm longer. In winter during the day may help in heating the home using the free solar energy provided by mother nature in the roof space ( can be 25 - 30deg in the ceiling cavity on an overcast day). Average homes cost around $3k to install and cost around $5 per month to run. Is barely noticeable and whisper quiet.
cons: cannot heat your home with the flick of a switch… but, it not a heater per se.
There are very good FAQ to be found at sayr.co.nz. Check it out.
June 9th, 2010 at 7:11 am
Jamie, what area do you live in?
June 16th, 2010 at 2:29 am
Newtown/berhampore.
June 22nd, 2010 at 9:14 am
Hi has anyone had an HRV system installed in a cold area do they work at night?. We had the HRV rep around last night who said the roof space would still be warm and the system would still be able to circulate air and work as it should. We live in Upper Hutt Wellington where we get down to 1 or lower some nights in winter so not sure how good HRV is in a cold climate? any suggestions or feedback would be really appreciated
June 25th, 2010 at 6:21 am
This feedback is very helpful. Has anyone had a Lossnay system installed, or any other system that draws air from outside? I already have a heat pump, but need something to reduce condensation, and warm up the bedrooms. But I’m worried about noise, and the cost.
June 27th, 2010 at 8:20 am
Brian, the vent is on the outside of our house therefore it does not take air from under the house. Air quality is amazing.
June 27th, 2010 at 9:30 am
Stu. An HRV, SAYR or DVS are all positive pressure ventilation systems. With out getting into the complete complexities of how they work, you have to realise they are not heaters. They are very good at reducing moisture and condensation and during the day time they contribute to heating your home with the energy from mother nature when it is available. During the evening, the better ones will automatically shut down to a fraction of their full speed. By doing this you still get the benefits of fresh filtered air but not enough to influence the temperature inside the home. If the HRV rep said that the airspace in the ceiling would still be warm at night, I suspect he either does not know what he is talking about or he is trying to deceive you. Basically around 5 or 6pm the temperature in the ceiling will be below the temp inside the house so there will not be a heating advantage. What you do have is a warmer drier home which is easier to heat and easier to keep warmer for longer. The air is clean and healthy. Dont be put off, positive pressure ventilation is a good investment.
June 28th, 2010 at 1:52 am
I had a PPV system “including heat recovery” installed 2 years ago. The sales rep and the brochure claimed that the heat generated by my Kent fire would be transferred to the bedrooms via vents in the roof cavity. This air coming out of these vents is still very cold in winter (despite the fire roaring) and blows directly over our faces during the night. There is still condensation on my windows when the outside temperature falls below 10 degrees at night. There is no noticeable difference in warmth throughout the house during the day. In fact, it feels warmer outside today than inside the house. I think the money would have been better spent on wall and underfloor insulation. Beware of exaggerated sales claims. I am still negotiating with the company to try and get this system removed from my house, it has failed to live up to the company’s claims.
June 28th, 2010 at 7:38 am
Unless your roof is sealed (which it won’t be) there is no chance of your roof being warm enough to give any benefit to you in the morning. Of course it will still be able to circulate air - that’s what it’s designed to do!
HRV just like DVS and SAYR and a multitude of other like systems is a ventilation system NOT a heating system therefore any heat you get from it is incidental and as far as I’m concerned any company that tries to sell off the system’s ability to heat is basically lying to you. We had HRV come to us (cold called) and used a damp meter to show us how damp our house was - When I asked the rep to show me proof of the meter’s accuracy or recent callibration he couldn’t/wouldn’t. I wonder why not!
I had a DVS in my last house and it was great at dispelling the moisture but useless as a form of heating. DVS never tried to sell it to me on the back of shady heatinig claims
I wouldn’t touch HRV with a barge pole because they have given me no reason to trust them and many reasons to not trust them. But at the end of the day - your choice mate
June 29th, 2010 at 8:20 am
Thank you for all the feedback, will look at probably DVS be a good change not having to wipe windows down every morning
July 5th, 2010 at 10:23 pm
Recent studies commissioned by EECA and Beacon Pathway, have shown again, that forced ventilation systems are being oversold on their benefits. The main issue I have is that these companies are selling a product and like any organization with a vested interest will be very unlikely to give an unbiased assessment of whether the product is needed or not. Reducing sources of internal moisture, heating, insulation, and natural ventilation should always be the first point of call. Beacons study of numerous homes has again shown that the basics should be assessed first, and that most NZ homes are leaky (draughty) and increasing the forced ventilation is usually not going to give an efficient result.
There are some homes, usually newer tightly sealed homes, where forced ventilation may be the only solution to bringing down indoor humidity. But again, you need to be clear about what the issue is you are trying to address. Damp, mould and “crying windows” are a sign that the damp surface is at a temperature below the dewpoint of the air inside the house. To deal with this, one either raises the temperature of the surface (double glazing and insulation effectively does this) and increase the heating, and/or decrease the moisture content of the air. Someone who comes to your home and sells you a $2k - $3k “solution” without assessing the symptoms deserves to be shown the door. You might be better spending that on a heatpump and dehumidifier and get the result you want and be warm too!
Anyway, buyer beware but this industry is a prime example of misleading information. They are large, sales driven, and prey on people’s awareness of symptoms rather than addressing the cause. There are cases where a ventilation system is a good option, but address the basics first.
July 8th, 2010 at 11:24 pm
I want to know if I should install a DVS system in my home to reduce moisture. The home is under 10 years old. I do not expect it to heat the home. Is there any negatives?
July 13th, 2010 at 9:59 am
I’ve just moved from Wanaka to Dunedin last week.
In Wanaka we were renting a two or three year old ‘designer’ house (cheaply clad) with double-glazing and gas fire in the living area which was also shared with the kitchen. In summer it was literally so hot we had to go down to the pool to lower our core temperature; so far this winter we counted up to five layers of wool on our top halves and two on our legs so as not to freeze. It was the most gruesome (actually the only) experience of new housing I’ve ever experienced. Wet windows every morning, mould flourishing in the condensation catchments. One room so cold it was crippling even with a fin heater. No difference between the brand new double-glazed house and the bach-style 1960’s fridge I stayed in a few seasons ago. Double-glazing is a rip-off if some monkey installs it.
Same by the sounds as these dry-air systems.
Here in Dunedin I found this site searching to see if anyone else had to turn off their MM (Moisture Master) system due to waking up thirsty as an Aussie. Our sweet, ugly 80’s brick rental has a little note above the control switch to ask us not to turn it off. I don’t know if I should or not- boy oh boy is it effective! I have turned it off over-night the last few nights simply because I can’t bear waking every few hours with such intense thirst.
We’ll probably go back to Melbourne but being a Kiwi I’d say without reservation that if I ever lived in another house here (lived in all the major centers and ski towns) there is no way I’d be without one of these systems. And a damn fine R.O. water purification system to remove the filthy fluoride from the tonnes of water I’d necessarily consume to stay hydrated.
Righto. : )
July 15th, 2010 at 10:02 am
Good PPV’s have many benefits. The amusing aspect reading a lot of these blogs is so many of the comments are clearly made by people who do have them or have not directly experienced them.
It is said time and time again that PPV’s are not heaters. Most people know this however a lot of the knockers sole focus is on this inaccuracy and bring it up time and time again. Sure, some desperate sales people will exaggerate this aspect but this alone does not make a PPV a bad purchase.
A good PPV helps remove moisture and a dry a home. The benefits from a dry home are many. A good PPV filters the air making the air inside the home cleaner than outside. The air in the ceiling is not recirculated, stale, old or the like. Air in the ceiling space is actually changed and flushed out more so than what is in the home. Roof spaces are designed to breath and air freely comes and goes. Because the ceiling space is relatively undisturbed it does gather dust and cobwebs but he air is fresh. A good filter will filter the impurities, making this air purer and cleaner than is inside or outside.
Drier air is easier to heat and stays heated for longer hence saving on heating costs.
Drier air inhibits mould growth and decreases the reproduction of dustmites making the home healthier. Good filters filter dust pollens, allergens and bacterias from the air being introduced again helping asthma and respiratory sufferers.
A drier home requires less maintenance, makes furnishings and furnitures last longer.
A home with a ventilation system is more secure.
Keeps flying insects out such as flies and mosquitoes.
These are just some of the benefits and everyone would like to have benefits such as these and I havnt spoken about heating.
Do PPV heat your home? who cares, i’ll have one for all the other benefits anyway.
July 15th, 2010 at 10:10 am
Janine. What size (kw) is the heater in your system and how long do you run it for typically for this time of the year. Since you are taking outside air and heating it, you must be using a lot of energy to heat cold winter air? Do you have vents in the floor if the unit is under the house?
July 19th, 2010 at 1:50 am
Hi Brian.
You do make good points, and I suspect you are involved with a company selling Positive Pressure Systems.
Correct, they are not heating systems, but this aspect is often pushed (by some companies more than others) as a way to sway the buying decision. I’d recommend staying well clear of any PPV company that pushes the heating aspect.
What’s also often glossed over is how location and building type / age can have a very big influence on which ventilation / heating combination is the best to go for. For example, Heat exchange ventilation systems really need a well sealed home with very low levels of air infiltration/leakage to work efficiently.
On the other hand, Positive Pressure Systems such as HRV actually rely on these natural gaps for the pressurised air to escape through, so I wouldn’t advise installing them in a more modern house (i.e. one with aluminium windows) unless you also install some passive vents as oulets. Otherwise you’d still need to open windows, which really negates any security & insect-proofing benefits.
And if you’re opening the windows anyway, you’ll most likely be getting more than enough ventilation by passive means.
July 26th, 2010 at 4:50 am
Brian, it is a 2kw heater and we run it for about 4 hours a day. Our power bill has never been lower as we only supplement it with a small fin heater the odd times. We used to run a 15 fin full bore and the bills were through the roof. We have a pole house so the system is not near the ground.. It’s a win win all around and we are extremely happy with it and wish we knew about it when we bought the house 9 years ago. I know of no negatives and could not conceive putting a system in without the heater unit..
July 26th, 2010 at 4:51 am
Oh, and yes we have two vents in the house…
July 26th, 2010 at 9:08 pm
Wanting an unbiased opinion from anyone who has had the Vent outlet heaters added to their DVS.
Do they improve the room temperature ?
Do they help with condensation issues?
What do they cost to run on a monthly basis
July 28th, 2010 at 2:20 am
Hey MATT.
Sorry I cannot agree with your comments regarding PPV in modern homes. Some of our happiest customers and most effective results are people with modern homes and even brand new homes. There are claims that new homes are air tight hence PPV will not work. There is no such thing as an airtight home. There are a multitude of places air can and will escape in new or modern homes. Sure older homes are ‘breezier’ which makes a newer home appear to be better sealed. We are yet to find an age, design or style of house that a PPV will not work effectively in. (obviously not flat roofed). There is the rare occasion where some PPV systems struggle and for what ever reason perform very poorly, these cases are limited and by far the majority of cases a good PPV will perform very well. Even a poorly performing system is still better than no system at all.
July 28th, 2010 at 2:27 am
Hey Janine
Thanks for your feedback.
I find it very interesting as I continuously come across people who have inline heaters in their PPV and they do not use them due to the horrendous power bill so its good to hear your happy with yours.
At 2kw x 4 hours per day at say 19cents per kwh, you would be paying approximately $47 per month (not including your fin heater). That is very good and I’m sure a lot of people would be happy with that.
I have heard of some people paying in excess of $300 per month with inline heaters in their PPV’s but they probably got a bit carried away.
July 29th, 2010 at 4:59 am
For us so far the SAYR system seems impresive.Is anyone really unimpressed?We live an hour south of Auckland.
August 2nd, 2010 at 7:00 pm
We have had a DVS installed for condensation not heating. Have found it useless and has made the room it was supposed to take the moisture out of worse. Have been told by the cfompany we need to heat the room for it to be effective. We were not told this when we purchased and wished we had never purchased it in the beginning.