DVS / HRV / Moisture Master / PPV Systems
I touched on DVS systems in my last blog and I will go a bit further today.
There are two systems that can take warm dry air from the roof space and pass into the home via ceiling outlets. The generic names are Domestic Ventilation Systems (DVS) or Home Ventilation (HRV). Do not get confused though with Heat Recovery Ventilators (HRV) which take warm moist air from the house and via a heat exchanger replace it with dry slightly less warm dry filtered outside air.
I will from now on call the DVS and home ventilation systems, which are the basically same product, the general name of DVS. These are also known as Positive Pressure Ventilation (PPV).
During a sunny winter’s day the roof cavity can get hot with the sun shining down on it. Clay tiles do not make the roof cavity hotter for longer than a metal clad roof and take longer to warm up.
What a very basic DVS system does is blow this warmed dry air via a filter into the house. This dry air pushes out, via gaps in windows and doors, the moist air caused by breathing, washing, cooking, etc.. Buying a dehumidifier to cure a moisture problem is useless as you are only getting rid of the symptoms of the problem not the cause of it. They have to be constantly emptied and are only reducing moisture in the area they are situated in. They also cost more to run than a basic DVS system, which is just a fan. Some people have found that they have had a reduction in their heating bills after fitting a DVS system. This is because it can warm up a home for the cost of just a fan running and it is easier to heat up dry air than moist air, as there are less water molecules in the air to warm up. Other benefits air that the air is filtered and can reduce asthma and allergy problems. If there is positive pressure inside a house there is less chance of pollens coming in. The most obvious addition to the system is to have a heater that takes the chill off as the air in the attic space cools down at night or on none sunny days. In most systems the heater just makes the air from the attic the same as the room temperature at best. With the system from Moisture Master you can have a 2kw heater, which on the highest setting actually blows hot air, but not enough to heat a house.
If you have got a pellet or log fire there is normally an option to take very warm air from near the fire and pump it around the rest of the house. This is a very low cost option as the whole house can be warmed up at the cost of running a fan. Obviously there is a thermostat that switches between the attic air and the ‘fire’ air depending on temperature. There is also a system that moves air from the fire area to other rooms. This only really works when the fire is going and for the price you would be better off buying a DVS system which can supply dry air all year round.
The last option is the summer option. This takes cool air from the South side of the house and blows it into the house. You could go out on a cold morning and shut all doors and windows tight and later the weather changes and your house starts to become hot and stuffy. With the summer option as the house gets too hot cool air is blown in and reduces the heat almost as if you had a window open.
The shape and size of your home and your family’s needs dictates how many outlets you have. As I have a long house I chose to have two outlets in the bedrooms furthest from the heat pump and one in the lounge at the other end. It is important to remember that these systems can give benefits even when there are no other heating or cooling systems in use. So if you are in Australia for 2 weeks in the winter you can come home to a freezing house. All the static air in cupboards and behind furniture, especially on the south side of the house, has come down in temperature to near the outside temperature. This cold air on your return can take several days to warm up. With a DVS system running, warm air on sunny days has been pumped all round the house and kept the overall temperature higher than it would have been. So do not rule out having an outlet in the area near a heat pump as you may not have to turn the heat pump on depending on how big your heating element is.
With any system that draws fresh air from the roof cavity or outside, which is then passed into the home, there could be a smell in winter, if you live in an area with lots of log fires. If you step outside your door on a winters night and you catch the sweetish aroma of smoke, that smell will probably be drawn into your home.
I have the Moisture Master system which has an automatic mode, but allows you to control the heater temperature and fan speed. So on a cold day I can turn the fan down to half setting and turn the heater up to the highest setting and nice warm air flows into the house. You must not have the fan setting more than the heat setting otherwise the air will not have had chance to warm up as it passes over the heating element. At night we turn the heating down to half and the fan to the quarter setting just so that the chill is taken off the night air. On hot days we have the fan on full so that cool air is blown in whether we are at home or not. On several days last year we had the system set to auto and with the heater on. Later during the day the sun came out really warmed the house up and the system swapped over to cooling.
If you suffer from ‘crying’ windows, thinking of buying a dehumidifier, constant cold hands even when the heat pump is on or damp and mould, a DVS system could be for you. There are various options so get various quotes and go for the option that suits you best. Money should not come into the equation as they could save you money and fitting extras later could be a lot more expensive. I saw a lovely expensive house with varnished wood everywhere; because of crying windows a very large internal wooden window sill had rotted. To replace that sill will cost more than a basic DVS system. Talk to people that have one and see what they reckon about it.
Remember with one of these installed can make your house more resalable.
May 09 2008 03:18 pm | New Brighton and New Zealand and christchurch
Patrick McQueen on 15 Jul 2008 at 11:51 am #
Hello Steve,
I find it interesting that you have bypassed the HRV heat exchanger ventilation systems so flippantly.
Taking roof space air is not the ideal solution.
#1 Christchurch mean air temperature in winter is only 9oC.Therefore the “heat ” available is not present.Yes the roof may be slightly warmer than outdoors but not as warm as the house so the overall effect is increasing the heating needs and cost of heatingof the house.
If indeed the roof has high thermal mass then this works equally well at retaining cold energy as it does heat energy.therfore it will take a lot to time for the roof to regenerate heat from a frosty morning start and with limited daylight in winter this often will force most Positive pressure systems to either shut off or run a expensive in line duct heater.bear in mind if the duct heater is used and it is say only 1kw then over the course of one month this can add over $100 to your power bill.
#2 taking away the thermal air break under the roof lowers the insulation factor that the roof cavity creates requiring more heating of the living areas
#3 The air in a roof space is contaimanated and unhealthy that is why there are noticeable smells in the roof when you lift the manhole various local and international reports are available to show roof space air is not suitable for ventilation.
NZS 4303 :1990 Table 2 specifies .35 Air changes per hour continuously from the exteranl enviroment.The roof is not an external enviromentand indeed with multiple downlights the air on a positive pressure system recirculates rather than drawing in new air.
#3 Under the systems you named DVS,HRV,Moisturemaster the air expelled outside also takes warm air with it.You have paid for this heating now you are expelling it outside,so this also has a cost that is never mentioned by the crafty salespeople who tell you its only 5cents a day to run.
Yes my company sells the other type HRV but not before we investigated oportunities to sell positive pressure systems.As we are a well reseached company we choose not to sell the systems that are blatently all fuss and wind and yes very profitable but not as beneficial as a genuine Heat recovery ventilator.
To Ventilate and dehumidify properley the air must be changed in the house.the Positive pressure systems have a generic fault in that no energy is actually recovered if it is not in the roof space it shuts down.Where is your ventilationthen.
Only a true HRV will keep ventilating and it will be cheaper to run that a DVS or moisturemaster when you take into account the actual energy losses these systems create.
I would welcolme you to put this on your site or contact me personally for further comment.
Regards
Patrick McQueen
Sales Engineer
Snowtemp Heating Solutions
Dion Glover on 09 Aug 2008 at 2:14 am #
I think there is a misconception overall that the Recovery systems are heaters or will take care of almost all your heating needs. The sceptisism will arise when the roof temperature is cool. Take into account that the overall solution to a warm home is a dry home, hense where Positive Pressure (with high quality filtration) comes into play. Air movement/adequate air changes gets rid of moisture. A simple mattter of replacing all their air in the house on a regular basis with air of a lower humidity. In a domestic situation, with a lower humidity; the overall comfort level is dramatically improved.
I think HRV have every right to advertise “Heat Recovery” in the sense they are tapping into a wasted, highly useable energy source; the wasted heat in your roof. One key word. Sustainability.
Doctor’n the House » Bought a House? What now? on 26 Oct 2008 at 10:10 am #
[...] can now look at heating the place. If it has got a log or pellet fire, look at getting a form of DVS system that can transfer that intense heat in only one room and put it around the house. Get the summer [...]
JT on 03 Nov 2008 at 3:01 pm #
I have experienced the HRV/DVS and Moisture Master and found that although DVS and Moisture Master are great to remove condensation the MM costs are expensive when the heater system kicks in and realitively using one vent does not work if you close internal doors. HRV does not support giving you all the heat but around 50 to 85 percent. Then you are to use your own heating just to top up on the really cold days. I am a csutomer of HRV and it really works! DVS and MM are great systems but heating the air in your cavity is more expensive than the 14-15 degrees in your home. Never has my home dropped below 17 degrees anyway. Hope this helps people make more educated decisions. Get quotes from them all and you will find out for yourselves. usually spending less gives you relative results as we all know. Cheers
Neal Williams on 14 Nov 2008 at 10:56 am #
You need to research carefully before deciding what system to install, unlike me! I had a basic HRV installed recently and was sucked in by the high pressure sales tactics. Claims of “never need to dust again”, “your house will smell much fresher”, were misleading. The dust still exists and now my house always has that musty smell of the hot insulation in the roof cavity. There is also the sound of the fan running constantly, which can get a bit irritating. Had I realised what I was going to end up with, I wouldn’t have wasted my $3000, and been left feeling as though I was pressured and sucked in by spurious claims.
Steve Taylor on 14 Nov 2008 at 5:28 pm #
I have got the Moisture Master system and have had no smells with the system. The only sound I hear is outside when the summer option kicks in on hot days and you can hear the air being drawn into the outside intake.
I cannot believe they claimed that you would never need to dust as dust is mainly human skin and no system would be powerful enough to blow dust away.
I take it from the price that you have a positive pressure system rather than a heat exchange one.
Stephan on 12 Feb 2009 at 12:22 pm #
Hello we recently had installed an Intelivent System which has the Heat Exchanger component as discussed above. Pretty satisfied with the results, the sales person was very clear on what the system can and cant do.
I can see clearly from the display, that the system is cooling our house during the evening, with these warm muggy evenings its been great. Looking forward to distributing the heat from our pallet fire in winter also. We actually purchased the system without looking at other options so could not comment on them. Our friend had Intelivent and actually pulled out the DVS system that he was unhappy with – so we went with his recommendation. The key thing I like with the concept of Heat Exchanger ventilation is that they work all the time, and do not stop of slow down at night time like positive pressure systems but instead utilise the heat in the house to distribute around and continually bringing in fresh air. I actually read recently that DVS is now putting out a Heat Exchanger system, and throwing away their positive pressure system… I guess that’s a sign of the times?
Sharia Wilson on 31 May 2009 at 7:04 pm #
Hi there Steve,
First i would like to say that i have recently got a HRV system installed and have had imnediate results, it works really good. I would recommend it to anyone. Also the one thing that made me go with HRV is that they have a 3year money back guarantee, so if Neal Williams dosen’t like his system he should ask for his money back. P.S thanks heaps for your website
joan on 20 Jun 2009 at 9:52 pm #
i have a HRV an since i got it i just love it my kids arent having restless sleeps cause getting fresh filtered air all night as much. The best thing about it is the burnt toast features because having three teenage sons feet tend to smell so i push burnt toast an the smells go away excellent i truly feel every household should have one it makes your home dryer healthier an has a hospital grade filter .Wuz happy about my power bills as well HRV HEAT RECOVERY VENTALATION is the way to go heapz of savings.
danny on 25 Jun 2009 at 5:25 pm #
I have an HRV as well and I wanted to return it because there is still condensation on the windows and the house smelt like the roof during hot days. And it was freezing during the cold nights. Wanted to swap it for the better ventilation systems. But when the hrv guy came around and I told him I wanted to return it he said I couldn’t. That the guarantee only covers fault with the system. But then I read around forums and people are saying there is a year 3 money back guarantee. An it says here http://www.productspec.net/company/2275/hrv.aspx that there is a guarantee. SO they must of changed there policy???
Mike on 13 Jul 2009 at 10:02 pm #
We had an HRV installed mainly to reduce to condensation overnight, and to enable us to keep all windows closed for security during the days when no-one is at home. It has done both of those. It has improved the air quality noticeably in the house. We normally don’t open any more than two windows even when we are at home, except in the summer. I have to agree about the hot smells during the summer months, and we have considered getting the summer option ducting. If the salesman had explained about the smells I would probably not have had it installed. We have noticed a lower temp during the night in the winter, which can be improved by reducing the fan speed to the extent that it does not stop the wet windows. That would have made me re-consider as well. I don’t normally notice the noise, and we have two fans. I don’t think that it helps to heat the house, we use the same amount of wood and power. On max fan speed you cant feel air movement at the vents (qty5) so the burnt toast thing is useless. Overall, not worth the money.
Oliver Range on 24 Jul 2009 at 12:03 pm #
I wondered if a ducted warm air system was better than a combination of a heat pump and a ventilation system (like HRV or DVS etc). My findings led me to conclude that the warm air system is much better, more benefits at the same costs.
A typical Ventilation System costs between $3,000 and $5,000, it reduces condensation, freshens air, reduces dust build-up, BUT it does not provide effective heating and it can fight against convection heating systems. For one Heat Pump to a heat a room, the cost is between $3,000 and $5,000, it reduces condensation, circulates and filters air, provides cooling in summer, BUT does not heat a whole home and suffers from reduced heating output in colder weather. So for partial comfort I would be spending between $6,000 – $10,000 (100-160 sqm home).
Alternatively, I can get a Bonaire Ducted Heating & Air Circulation System for the same cost. This will reduce condensation, circulate and filter air, reduce dust build-up, provide a cooling-effect in summer, effectively heats a whole home, heat different zones, at different times/temps, maintain heating output in colder weather. What’s more it will use NZ’s natural resources more efficiently and effectively, it is an Asthma Foundation NZ approved product. I know which sounds better!!
Unlike Heat Pumps, there is no need to go into chilly defrost mode, plus you can enjoy quiet air distribution from many ducts not just one big blower.
Unlike Ventilation Systems, warm air reduces condensation, plus effective heating is provided efficiently on demand (you should not have warm air in your loft in winter in the evening as decent ceiling insulation should keep this heat in your rooms). So to benefit from Total Comfort I will spend between $6,000 – $10,000 (100-160 sqm home).
A warm air system is much better.
Neal Williams on 15 Aug 2009 at 3:37 pm #
Just an update on my HRV. It’s been a year since I had it installed. The smell hasn’t improved a bit. At no point over winter has the roof space temp exceeded the house temp(so no heating). It doesn’t help distribute “stratified” heat as claimed. Temperature variation of 13c from floor to head height. So much for Marc Ellis’s claim of no cold feet!! Though it’ll be hard, I’m going to pursue a full refund based their misleading (false) advertising.
Bryan Beecher on 28 Sep 2009 at 11:03 pm #
Re the summer option
why not just put the fan in reverse
warm air form the ceiling is pumped out
cool air enters the house via doors and windows
sounds simpler to me
paul on 16 Nov 2009 at 8:06 pm #
Iv been looking into a DVS HRV Moisture masta etc and after having the salesmen come to the house and all saying that there system is the best and that all the others were rubbish..!! iv been in the building industry for 3 years and have helped to build 3 brand new homes in christchuch and do a few major alterations on older homes etc… so i do know a thing or too about a houses.. I have come to the conclustion that a brand new house is the only way to go and an old house will always be a problem to heat and get rid of condensation etc.. the thing is a new house is Fully insulated generuly with a concrete floor and double glassing,and properly laged water pipes and much better exterier cladding..
Older houses have a million different things going on that create the problems that we spend lots of money on trying to fix but at the end of it all they’r still on old house unless the owner completly strips it and rebuilds it with better materials and better insulation etc… so the old salesmen selling these DVS HRV etc are having a field day with all us old house owners…
The moral to my story is if you dont have a new home you will always be spending money trying to get it to perform like a new home.
P.s. dont trust what a salesman tells you because he or she just wants that sale but if you realy feel that they are selling what your home really needs and there is a money back guarantee then maybe you should go for it, but do as much homework as you can.
RAHUL on 13 Dec 2009 at 9:17 pm #
If you guys had been sold the actual ”hrv” system then you should have heard the sales person telling you that ” it will reduce your enegery cost up to 40% ”. any body in their right mind knows that atleast 40% of the time it is actually going to be some what warmer in the roof cavity, not to mention, that it will always be drier and drier air is always going to be warmer than the wet shit we have in our homes. Even if it is only a degree or 2 maybe 3…nothing to complain about having 3 degrees in crease in temperature for free in every room aye. heat exchanger…..well the concept of having a drier warmer home is not rocket science. ” HRV ” offers a very simple soultion to a common problem. Wet clothes wont dry themselves out if you leave them in the washing basket, you need to put them on the line. Its just air movement.
And new homes…..LOL, brick or some stucco shit that sits on 50,000 litres os moisture (concrete slab), alluminuim joinery, double glazzing, pink bats from head to toe-its like a petre dish!!. Its just making them too air tight!! Give it some lungs.
Anyone that is looking into a system. speak to your local HRV. With 80% of the market share, they muust be doing something right.
Stuart on 14 Dec 2009 at 10:24 pm #
Thank you Rahul for your insight above. I’m would hazard a guess that you are a sales person for said “HRV” company. I have had a few years of experience selling true HRV ( Heat Recovery Ventilation) systems along with many other products on the market including but not limited to, Hydronic Underfloor Heating, Solar Thermal Systems, Photo Voltaic systems, Ground Source Heat Pumps, Air to water heat pumps, Double Glazing and Air to air heat pumps. Most of which was done whilst working for one company which is my point. You are all trying to do a number of things with one or in some cases two products/systems. There is, in my humble view no one silver bullet, it is a case of a number of different systems ( insulation being one of them) being used in conjunction with each other.
Think for yourselves, do any of you have mould on the ceiling in the corners near outside walls, if yes, check your loft insulation. The cold air in your loft is cooling your ceiling on top, which has warm air from your heater/heat source, breath, underneath this in turn will, if the temp variance is over 7 degrees, create condensation. Thus, mould over time. Same sort of thing for single glazing.
All the systems mentioned above have some benefits but some systems are better than others. To some extent you pay your money you get what you paid for. That said there are a lot of spotty salespeople around drinking too much Redbull, talking bull and charging like a wounded bull. Read some of the unhappy text above.
I suggest getting a good heat source ( log fire if you have plenty of trees or if not then maybe a heat pump in the lounge and hall for example) along with a true Heat Recovery Ventilation System ( not to be confused with the company “HRV” unless they have started selling units with heat exchangers as well). If you have the money then replace your windows for double glazing and oh yes lets not forget the insulation in the floor, roof and walls if your removing plaster board/renovating. The facts and relevant tests have all been done for us it’s just a case of finding the info on the web, working out what money you have and getting the best you can afford which, at the end of the day is what it’s all about.
Something ,is better than nothing. Personally I would insulate more.
paul on 03 Mar 2010 at 9:06 pm #
Hi there Nick, since you know so much about HRV can you please explain why some people complain about the musty smell that comes from the roof cavity that the filters dont seam to stop..??? and what about in the middle of winter when the roof cavity is cold..that cold air is pumped straight into the house forcing any warm air out through the gaps that exist in the windows,doors etc… (that is why some companys offer the heater in the roof to heat that cold air) (though it cost a lot to run these heaters)
and the cost of these units…??? why are these units so expensive when its only a few plastic vents, some piping, a fan and a switch to turn it on & off..???? all that dont cost $2500-$3000 more like $400-$500…
sorry but i just dont get these roof venting systems when they’r so costly and imperfict..
i do belive a customised venting system that works with a heatpump will work well and shouldnt cost more than a grand installed…
BUT hrv dvs and all the others want large profits and thats all..
am i right nick..???
Jeni on 11 Mar 2010 at 6:39 pm #
Hi Paul, I thought I would throw my 2 cents worth in as well. If you dont mind the opinion of a woman? lol. I have had a number of ventilation systems in my houses over the years and swear by them. And have seen the difference as technology has progressed in the ventilation world. Started off with basic DVS systems, then tried DIY setups (your $1000 model)(typical Hubby special) and then the more modern DVS. Finally I have started using HRV’s. The difference is chalk and cheese. All do something, HRV’s made the largest difference by far. To the extent that because of the changes in my house, my parents have traded their DVS in for a HRV. (Suprised me too that HRV “tradein”). They couldnt be happier. From research and experience I have come up with some answers as to why. DVS and others use low grade cheap fans. The amount of air flow is limited. Even on a warm roof day I could hardly feel the difference in temperature throughout the house. HRV fans are much, much more powerful, they even use multiple fans in larger houses. Any heat in the roof now comes in very very quickly. Obviously far more drying is also done with more airflow. Secondly, HRV fans have 21 speeds and are a proper “smart” variable spped system. If its cold in the roof, HRV fans will slow right down and even shut off in extreme cold. No cold air coming in. My modern DVS never switched off. I had to manually. I’m a V8 girl so I understand horsepower. HRV’s have plenty. I also like computer fuel mapping vs old school carb setups. HRV is as modern as you can get.
As far as musty roof cavitys. Good filters will remove most things but cannot remove odours. Odour particles are too small. So use carbon filters to scrub out odours. Most good ventialtion systems have these available. We used them with a moisture master last time. HRV have add on carbon socks for problem musty smelling roofs. A friend had this problem with hers. Problem now gone. I live in New Brighton, Christchurch and my HRV never, repeat never brings in frosty cold air. And I still dont get condensation!! Used to stream down the windows.
In summary, anyone who goes out and thinks they can buy a cheap nasty fan, some basic drafty vents, a dumb two or three speed therostat switch and expect good results should be laughed out of the building. I should know since my husband has done this already lol haha. $1400 down the drain.
This is all very, very simple stuff Paul. For a man who professes to know a lot, you are asking pretty basic questions. It seems more like you have an axe to grind with HRV or perhaps you work for a heat pump company. Whatever.
For anyone else out there, you get what you pay for. Personally I reccomend HRV, and since then, most of my friends and family now do to.
Clay on 19 Mar 2010 at 12:57 pm #
PPV Systems like the DVS and HRV only work well in homes that are airy.Why,because the more gaps there are in a house the quicker the old stale damp air will disperse.It will also help if your house is not damp underneath.If it is get it damp proofed to stop the moisture rising into your house.These systems should not be installed in new air tight homes as they would not work and will course long term problems.
IMO when they asses a home they should take the above into consideration.They should also test the air temp and humidity throughout the home.This would give them an indication of which parts of the home need more attention.
They should also fit carbon filters on all these systems.This will stop attic and outside odors from entering the home.
And finally these system are primarily for ventilation,not for heating and cooling.The heating and cooling features are a bonus and work to a certain extent.
paul on 19 Mar 2010 at 8:39 pm #
Thanks clay..!! finally someone who knows what they are talking about.!!! now if only someone could set up a business where they custome make a system for the indavidual home that needs a proper air siculation pump and charge a resonable price id be all for it, i do realise that HRV and the rest do change things a little for each house but they dont test the air quolity or do other things that would make the air pumps work to there full affect.. though im sure HRV and the others do get it right from time to time they still over charge for a ferly simple setup.. after having 4 different sales man come around to my house and saying this is what you need and ours is better than all the rest (without doing proper checks) and a charge of $2500 to $3500 i just stoped looking. I have just had a heatpump installed so ill be seeing how much differance it makes to the house before going any further.
Clay on 19 Mar 2010 at 9:16 pm #
Paul,while you are enjoying the benefits of your new heat pump you should look into the cheaper systems.
If you do the following a cheap system will work just fine.
1*Damp proof underneath your house.
2*Put extraction fans in the kitchen and bathroom,both vented to outside.
3*Vent your dryer to outside when you use it.
4*Don’t dry clothes inside.
They sell some at bunnings and mitre 10 for under $1000.Theirs also a system called smartvent which sell for about $1500 and comes with a 5 year warranty.
Jason on 27 Mar 2010 at 1:20 pm #
Hi every one there sounds like there is a lot of debate over system’s and it is not very good when people on here make you think they know something and tell people stuff that is not true about how it only works best in old houses and not new homes. Well new homes are very airtight and during winter you have your home all closed up, and with each person in the house producing 5 litres of moisture a day (example: 4 people 20L a day 20×30=600 Litres per month) damn who wants all that moisture in your home this is proven and can be found on the consumer website, so every home needs a ventalltion system to get rid of moisture problems in the home. It not just about that, it is also about providing a healty home getting rid of air pollution in the home. Air pollution is twice as high inside a home than it is outside so what you see outside on a winter’s day is twice as bad in your home just invisble so who wants to breathe that in?
Go to TDC website if you want to research that it is proven. Example there are two glases of milk one is 3 days old and been left out and one fresh from the fridge what one would you drink? Exactly that same as the air in your home clean fresh air will make you live longer and more healty. I personally have a HRV SYSTEM they are brilliant. For everyone who says HRV systems are crap and dont work they have 95% market share and have been approched by the american government to bring there eco friendly product over, so if it didnt work why would they be being approached by the Americans?
HRV systems are all NZ MADE and only the fan is imported from Germany which is made by Mercedes Benz and they use the highest Grade filter avalible and HRV are the only ventalltion system backed by the ASTHMA Foundation for everyone that says a HRV does’nt work They do work and they are in Over 100,000 homes in NZ now
Charles on 27 Mar 2010 at 1:57 pm #
Hi all,
Reading through these posts is really interesting – a lot of good and some not so good, some from high expectations caused by sales pitches and some from a lack of understanding.
Those who are only working on what they have been told or working on theory would be better to go and (with an open mind) spend at least a week in a house with a modern well set up ventilation system. You will notice how awake you feel in the morning (not stuffy from having the window closed and not cold from having the window open).
You should not need an electric blanket, the bed will be dry and quick to heat with your body temperature (especially if the ventilation system has been installed for at least a year – it takes time to remove the moisture that you put into your home).
A modern new home as mentioned above this is an interesting one….. All homes were once new and therefore dry, I built a new home in 1988, I insulated it both walls and ceiling (better than existing standards at the time). I had a wood fire, but I did wonder why it was a colder home 5 years later. I did not come up with the answer at the time. I moved on and as life went on I moved into a ‘modern’ home in 2003 that was built in the mid 90’s. It had a condensation problem and was hard to heat, because of the home design a heat pump was impractical, inner city a wood fire was not the go.
So I asked plenty of questions (NOT many people know the answers as they are selling product only) some homework was done, generally this ‘new’ home of mine was damp, I had plenty of condensation, I was heating water before I got warm. I installed a positive pressure ventilation system (vented into each bedroom and living space and sized for the home) It needed to be able to vary the fan speed in relation to what was happening in both the roof and the house.
That winter the condensation disappeared (great) The benefits the next winter were even better, less heating at the beginning and end of winter – it still needed heating when the weather was cold – and my other half found she did not need to use the electric blanket and the flannelette sheets were not used, we had less sniffles and time off work. It is now a far better home to live in.
Yes these ‘new’ home are far better than they have ever been (especially now, I hope we have got through the leaky home problems) BUT they will always have moisture problems from the inside – WE are living in these homes… and we need to remove the moisture as it is being produced.
All fabrics, carpets, gib-board and furniture absorb excess moisture. Initially your ‘new’ home may not have condensation problems but once these items effectively become saturated the dampness will start showing, initially your bed will need the electric blanket – we perspire about 500mls per night, then clothes in your wardrobe won’t feel as fresh as they once did, then on your windows as condensation will first be seen on the coldest part of the house, then on other parts of your home and in 20 years time the same comments will be made of your home as we are making about 20 to 30 year old homes today, that they are cold and hard to heat.
I did not believe I would ever say that, but as I have more experience with houses, I continually see it happening, one lovely old villa (friends of mine) yes it was cold – had plenty of holes – was renovated about 10 years ago, it was striped, re-cladded insulated and relined to the new home standards at the time. They were impressed and had a lovely warm new home and an old villa. Three or four years ago they started to get more condensation but accepted it as that’s what happens, two years ago they were saying it’s getting harder to heat, many comments were made, from “oh we’re getting older’ to ‘it was a really cold winter last year’ when really the problem was the house was holding moisture and it was costing money to heat it out.
Needless to say I suggested the installation of a ventilation system, they are very happy and have got their ‘new’ – old vllla back.
A controlled ventilation system is NOT a fix or replacement for bad heating choices, wrong or bad insulation, or a leaky building, it is only part of making a healthy stable efficient home.
Any heater can heat a home (so long as the heater is big enough) but it could cost a fortune to run, especially when it has to firstly dry out your home….
Opening windows gives you ‘fresh air’ but it is also full of dust, pollen, pollution and moisture – in the winter AND summer.
Insulation is fantastic at keeping the heat in or out of your home, but it can also keep in the moisture. Double glazing is part of insulation, it keeps the heat in or out, stops condensation forming BUT does not stop the humidity inside your home causing the home to become more damp and unhealthy. Another thing I’ve noticed, people with double glazing generally don’t open the windows as often, I’ve been told ‘I don’t open the windows these days I’ve got double glazing and it’ll let the warm air out’ She had bad mould in a 3 year old home.
So a balanced combination of all three is best for you, your family and your home. Give your home too little or too much – heating and controlled ventilation or too little insulation and your home, your family or your pocket will suffer at some stage.
pete on 12 Apr 2010 at 12:30 pm #
What a waste of good money @ over $3000 just to have a bit of wind in your house via HRV etc;
just can’t beat a good heatpump to get rid of the moisture / dampness at half the price.
David on 12 Apr 2010 at 1:27 pm #
I’ve owned two HRV’s, one in Dunedin and one in Chch and they worked fantastic. The one in Dunedin dropped my heating in winter from $890 down to $285 the following year in a colder winter and I had an unpainted iron roof that got any sun that was going even though the house itself lost the sun.
Now in Auckland I have found a SAYR system that uses the same german fans and has the same output in airflow but with a 5 year warranty, a satisfaction guarantee and a cheaper price than HRV. Also has a really smart touch screen controller. SAYR will let you instal replacement filters yourself to 40-60% over HRV’s price and they are .3 microns not .4 microns so are now the bets on the market. In fact, HRV people can buy thse filters cheaper too as they fit the same box the fan unit is in. These SAYR systems look like the best deal for the best result I’ve seen or experienced yet.
Brian on 13 Apr 2010 at 10:14 am #
Hey Pete
Heat pumps are terrific. But they do not remove the moisture or dry your house. They do make half of your home warmer and other half luke warm, at a price. By warming your house the moisture is mobilised but it is still in the air, it doesnt ‘vanish’ unless you remove it from the home. Heat pumps and ventilation systems do entirely different things. They both have advantages over each other. It is widely known that the average family puts in around 8 liters of moisture a day into their home. If this moisture is not removed it can cause mould and encourage the reproduction of dust mites to name only 2 of many pollutants which can make your family ’sick’. Pete, I would be very interested to know how a heat pump removes this moisture. I endorse Davids comments, I have now had 2 ventilation systems and they are great. I would definately recommend them. I do agree, HRV do tend to be a bit pricey but you dont have to spend that much. Just like heat pumps, you can spend $2000 or $8000 so saying heat pumps are cheaper is misleading.
Mike on 14 Apr 2010 at 9:14 pm #
I have a new HRV and am getting a musty smell from the roof cavity. HRV said it would cost me $100 for each outlet. They also said that they weren’t t that good at getting rid of the odour. Has anyone had any success with these? I need six of them. HRV claim the smell is probably due to blocked guttering?
Mike on 14 Apr 2010 at 11:06 pm #
I’m talking about carbon socks as mentioned by Jeni on March 11, I didn’t make this very clear in my post.
jay on 20 Apr 2010 at 9:52 am #
The filters are about 500mm long carbon socks and fit in the outlets on the box in the roof,so you would need 2.They just minimize odors and also restrict airflow a bit.They only last around 6 months.Your best bet would be to find the source and eliminate it.
Mike on 21 Apr 2010 at 6:32 pm #
Thanks Jay – I think you are right. I didn’t realise the carbon filters would have to be replaced so frequently – an expensive option indeed.
Herb on 22 Apr 2010 at 7:29 pm #
Hey Mike
Good Positive Pressure Ventilation Systems will filter out the bulk of dust, allergens, pollens, bacteria and pollutants however if there is a problem such as a bad odor from an abnormal external source in the ceiling, its unfair to expect this to be rectified. Odors in the home like people, dogs, cooking etc are expelled. Any problems in the ceiling will need to be fixed first. Although carbon filters are good, they are expensive and don’t last long they are overkill. A reasonable grade filter such as fabric pleated F7 is in most situations all that is required. Some companies use lower grade filters which are still better than nothing but limit the effectiveness of the system.
Best of luck in finding the cause to your odors and a good start would definitely be the guttering.
Nicola on 27 Apr 2010 at 11:34 am #
I had a Sayr person knock on my door last week. They said what david suggests that it uses the saem fan and equipment as the HRV I had explained to me recently. I’ll eventually buy the Sayr as it’s cheaper and has a better warranty yet puts out the same airflow with the same number of vents (so the person said).
Apart from not being able to afford one yet, the HRV person was super pushy. I’d recommend the sayr people as apart from being cheaper, they seem far more interested in you than the sale.
» Heating-Cooling-Ventilation? on 02 May 2010 at 9:36 am #
[...] I’ve been reading a hotly contested blog post http://unconditional.co.nz/dith/2008/05/09/dvs-hrv-systems/ [...]
Andy on 02 May 2010 at 11:55 am #
I have just read that ‘hotly contested’ website. Whats hotly contested? Sounds like a promo site for HRV. If you want unbiased opinion, stay here. This is a great forum. Keep it up.
Darryl on 12 May 2010 at 8:48 pm #
Very interesting website and information and opinions and experiences. Does anyone have any experience with SMART VENT ?
Brian on 13 May 2010 at 12:44 am #
I know a couple of people who put in Smart Vent. They were frustrated with the lack of response from the system controller. Basically it sounds like it is not smart enough and the it is still too much of a manual system. It is or can be a DIY system. It is cheaper than the real ventilation systems like HRV, SAYR or DVS but you would be better off spending a bit more and have a professional system installed. One of the Smart Vent systems crapped out just after 2 years and the electronics have to be replaced. My mate hasn’t done that yet as he is considering having another companies electronics control the system but I dont know if that can or could be done.
Mike Wilson on 15 May 2010 at 11:56 am #
Hey Herb
Thanks for your reply. I’ve cleaned the guttering and I think there is a bit of a positive difference. The odour is not as obvious now as well because of the cooler temperatures but it’s still there especially when you come in to the house when it’s been locked up for the day. I’m gonna get up in the roof and check it out for myself.
Steve Taylor on 15 May 2010 at 12:13 pm #
Hi Mike,
Try turning off the system when you next go out on a warm day with the house locked up and see if the smell is still there. It might be something in the house that was recently introduced. Also remember that if you get a smell on cold days/nights that can be the outside air being filled with the smell of log fires that is being drawn in.
Mike on 18 May 2010 at 11:16 pm #
Thanks Steve but it is an odour from the roof cavity – I can smell it when I get up into the roof space. I’m going to wait until it’s a bit cooler up there and get up and have a good look to see if I can identify the source. Maybe roof rats – I’ve been baiting them.
Herb on 21 May 2010 at 7:20 pm #
Hey Mike
It wouldnt hurt to put in a couple of soffit vents. These are say 200mm vents, one on the southside, one on the north. Your roof space naturally breathes but these will ‘help’ it breathe. What you are doing with a PPV is to flush your house of toxins and pollutants, it does not hurt to flush your roof space as well. It should not cost a lot for 2 vents. Let me know what you can price them at. If its too much I could help. These are simply put in the soffits, no ducting or extras, it simply helps the roof space breathe. This breathing could and I’m sure will help flush out these odours. If nothing else it will help your PPV be more efficient.
When a new PPV is installed you do get odours for a time. Some take longer than others.
AJB on 26 May 2010 at 12:30 am #
First of all I am not associated with any PPV or HRV system. I am however associated with the building industry and have spent many years in Europe.
I think all systems can have a positive effect on the internal environment. But no one has mentioned that a true heat recovery system with heat exchangers are available up to a reputed 85 – 95 %. These have been extremely popular systems when coupled with passive house principles of reduced energy loss. Energy losses can occur through external joinery, wall systems, lights placed in ceiling where air flow can pass from draughty roof space into house and floors. Thermal bridging adds to energy loss through elements such as cladding to frame, external joinery fastening and design inadequacies. Remember, wall insulation is only between studs!
Heat exchanger systems benefit from energy acquired through solar gains, heat created in the bathrooms and kitchens. In effect, increasing the efficiency even more. Almost everyone cooks and takes showers, This assists these systems to provide a regulated air temperature with nominal fluctuation when mixed with incoming fresh air that has 85 – 95 % of the air temperature that has just been extracted. This demonstrates true efficiency in my mind. This also allows the system to function at night to regulate temperature.
This is not the case with non heat exchanger systems. Warm air gathered from the roof space is wasted through extraction to exterior. Money spent on inducting warm air into house is wasted. When the roof space drops the other systems stop, where is the clean dry air then? No air flow = decreasing air quality. Energy used to warm water for the bathroom and cook food on the stove is simply pushed out of the house, I simply dont get it?
Yes, all systems can provide clean dry air with correct design and materials but the question must be asked, do you want a system that can operate for up to 90% of the cost of normal heating, or a system that drags warm air in from the roof but only when the roof is warm and extracts it outside to warm the gardens.
This is my opinion, I dont mind if people dont agree, everyone is allowed theirs. It is also my opinion that the investment in a house is normally the single biggest investment humans make, the environment we live in is extremely important to our health. All stake-holders in the construction industry need to be responsible for this, passive houses are the way to the future, through careful design, specification and construction, we can all ensure our so called clean, green country really is clean, green and healthy.
Herb on 27 May 2010 at 2:01 pm #
For whats it worth this is my opinion and I too have an extensive back ground in housing design, building, electronics and fluid dynamics for over 35 years.
Heat exchangers which recover existing energy within the home and transfer this existing energy or heat to outside air being bought in do work very well however there is a significant loss in heat during this process.
You need to have a primary heat source to work in conjunction with these systems. i.e. 20 deg inside is converted to 16 or 17 deg during the process. This in turn during the process is converted again and unless this incoming converted air is topped up it will eventually end up leaving your home cold. Even the best systems only have an efficiency rate of 85%. Which is the system claiming 95%?
What you have to factor is what is the outside air temp at the time, what is the air speed in the system at the time, how long is the ducting and how much resistance is there in the ducting. This can equate to a % base energy loss in the system prior to and after the heat exchanger, coupled with an 85% efficient transfer system, you end up having a system that effectively converts 85% (transfer systems efficiency) of % base energy loss (energy which is left over after whole system loss) which equates to not much.Hence you need heating source as well.
They don’t warm, they are expensive and you need primary heating source to work along side.
How much heat is recovered from taking a shower. So you are saying you put a heat exchange system in, take a shower and its going to warm your home. I am sure it will but in how many ‘tenths’ of a degree will it contribute.
Roofs are designed to breathe and have fresh outside air constantly flowing through. It is the uneducated which say roof air is stale. What you need to do is ask people who have a reputable PPV system (there are not many good PPV around) what they think. Make your mind up what system best suits you. Also ask yourself why are so many are being installed into thousands of New Zealand Homes and the bulk of these sales come from friends referrals, that speaks for itself.
PPV have come a long way in electronic design/performance and operation very recently and a lot more has been learnt how to increase their efficiency and performance. Older systems which many are still out there do not perform that well and have left some people disgruntled with the performance. The latter systems do not keep cranking away when the air is cold in the ceiling space but they do keep the air circulating by a trickle which is not enough to effect indoor temp yet is enough to combat damp and moisture.
Heat exchangers are very effective in countries with much colder, danker climates such as parts of Europe, Canada and the like. Hence, you find lots of them. Modern, effective PPV which are very popular in NZ are now finding themselves in south Australia, parts of mid US and enquires are being fielded from South Africa and Brazil. Hmmm, interesting.
Not wanting to name brands here but since AJB is plugging Smart Vent: Smart Vent has one of the lowest fan outputs for house volume in the market, the controller is a three speed fairly basic device which does work but it could be a lot smarter. I know Smart Vent has a top of the range Synergy system that is considered effective but what do you pay for that? 5 or 6K and then still has to have a primary heating source working alongside. I have not heard many positive comments from people I know who have had Smart Vent and then tried other PPV systems (when moving house etc), all ventilation systems when used correctly are better than no ventilation systems and I am including Smart Vent and heat exchange systems.
You dont have to be an electrician to acquire a Smart Vent system, just pop down to the local Bunnings hardware and the like and take a look at whats on offer, you can DIY.
PPV systems have their advantages and disadvantages, but at the end of the day are simple yet highly effective home conditioning systems which are cheap to run and do help make your home warmer, drier and healthier.
I believe newer modern PPV have their place ahead of Heat exchange systems in NZ.
Brian on 27 May 2010 at 2:28 pm #
Herb
I hear where your coming from.
We have recently put in a new Sayr Ventilation system, I must give them a plug as it is just as you say.
We have had others before but they were like the model T ford of ventilation systems, they were ok but not as good. Have a look at their website and read the testimonials. (mine is from my wife, Lisa).
AJB on 27 May 2010 at 11:14 pm #
As I said everyone is allowed an opinion, hopefully people can form their own conclusions.
Firstly I do not support any brand or system. To be totally honest I have never heard of a Smart Vent system, with respect to your opinion Herb, you are totally wrong on that account. Neither did I claim that Heat recovery systems heat. Heat Recovery/Exchange systems benefit from the heat produced in the internal environment. This in turn helps to keep heat in the system which is circulated continuously. It stands to reason that both PPV and Heat Exchange systems remove moist air which in turn creates a drier, healthier and warmer home.
PPV systems are going to work better in warmer climates because the temperature is higher on average. I would have thought there is no need to recover heat. I wonder what kind of systems you actually design or use, it does seem PPV gets your vote whether objective or not. This is not a sales pitch and I never did push either system.
It is also a fact that roof spaces in NZ are designed to breath and I absolutely agree. If you are familiar with buildings in Europe, because of the colder climates the buildings are considerably more efficient. This is attained through construction techniques which increases air-tightness and insulation.
It is also a fact that Heat Exchange systems are more expensive, but no one seems to take into account the benefits of use over time. Circumstances do play a part in this, as we in so called clean green NZ like changing houses more regularly than in Europe.
You bring up issues like outside temperature, type of ducting and length, air speed of the fan. Do these issues not apply to all systems.
Is it not a fact that PPV systems also need a heat source? How does the PPV system use this heat?
Is it not logical to suggest that Heat exchange systems will require less heating than PPV systems if only for the simple fact that PPV systems waste this heat energy.
Using counterflow heat exchangers and very energy efficient ventilators (using so called EC-motors with extraordinarily high efficiency) recovered heat is 8- to 15-times higher than the electricity needed. Again these are more expensive but it is similar to current solar panels which have a long payback period. There are Heat Exchangers in Europe with close to 100% heat recovery, factoring in base energy loss, up to 95% system efficiency can be attained.
I point out that these systems are installed in specifically designed houses which is another key difference in New Zealand. Our legislative system with regard to house insulation and efficiency has lagged a long way behind other OECD countries. Having been changed recently homes will become better equipped to handle our natural environment.
Yes, PPV systems have come a long way recently, I believe this is attributed mainly to better control systems and higher quality units than anything else. It must be acknowledged that there are common materials in all systems, but NZ is typically known for cheaper alternatives than future benefits.
Everyone has their own objectives and circumstances when choosing a ventilation system, they all have advantages and disadvantages. Again, it is not my intent to push a certain system, but I do believe that more emphasis needs to be put into functional efficiency and not always based on cost,
Thanks and goodluck
Herb on 28 May 2010 at 12:57 pm #
Thanks AJB
Without going into great lengths to explain how a PPV ‘helps’ make your home warmer (I AM NOT SAYING IT HEATS YOUR HOME PER SAY FOR ALL YOU KNOCKERS WAITING TO SLAG ME) and to keep it very simple: A PPV takes the heat energy from the ceiling in winter when it is available and evenly distributes this through a house. e.g. On a typical winters day by 10am it can be 12deg C outside, roof cavity can be 22+ and during the course of the morning through to 1pm ish it can get as high as 28deg C.
By mid day with this energy available the home can be around 21 -22 deg C. It is warmer and drier and this is without any other heating source. You have started the evening with a warm dry home requiring a less amount of primary heating.
I am not going to get into a heated debate with others on this forum who want to debate the fact that this happens, it does, my house and heaps of others are factual proof.
AJB I would dearly love to know what brand of heat exchangers achieve close to 100% efficiency? How come ones available in NZ range from 70 to 85% efficiency, why dont we have these 100% er’s here.
AJB to answer a couple of your statements:
AJB – ” You bring up issues like outside temperature, type of ducting and length, air speed of the fan. Do these issues not apply to all systems”.
As a PPV is not a heat exchanger it is not required to have insulated ducting and act as a heat exchanger would. When the outside or roof air temp is not providing energy the clever PPV systems shut right down to minimal ventilation not affecting temp so they dont exhaust any heat gains into the garden.
AJB – ” Is it not a fact that PPV systems also need a heat source? How does the PPV system use this heat? “.
I covered this briefly in my opening paragraph. This is without any other heat source. How would a true HRV obtain this kind of temp without a primary heat source, it cant. So it is not a ‘fact’ as you questioned.
EC motors are extremely efficient and cheap to run.
PPV systems (once again, better ones) cost approx $6 per month running 24/7 for homes up to 120sqm. Thats pretty good ?
If homes in NZ were built and maintained better then there ‘could’ be less reason for PPV’s however they are not hence PPV being required.
People seem to get hung up on focusing on PPV claims of heating. You have to realise that is not what a PPV has been designed or intended to do but as a side it does aid in helping the warmth of a home. There are approx 10 other benefits you get from a PPV, not just the thermal factor.
This is a good discussion AJB and there is no personal criticisms intended. Just healthy opinionated banter.
Thanks also.
Richard on 01 Jun 2010 at 12:04 am #
Why is it that I had a true Heat Recovery System installed in my character house and it did not work. I eventually got my money back after 3.5 years after they admitted had they initally realised that my house was a concrete block cavity constuction in the first place they would not have fitted the Heat recovery System.
Now 4 years down the track I’m still no better off!
Any suggestions?
ps they tried using air from ouside the house as well as the the roof cavity still with no effective results.
Steve Taylor on 01 Jun 2010 at 11:52 am #
Hi Richard was the Heat Recovery System the type that recovers heat from the interior of the house or only from the roof cavity?
Richard on 01 Jun 2010 at 6:49 pm #
Hi Steve,
The system I have is a heat exchanger system, and not the positive pressure DVS, HRV-type systems.
Initially it was configured to transfer the heat across from my internally sourced warm but moist air from my kitchen to the supposedly drier air from my roof cavity, and then redistribute this around the house – while expelling the now moist but cold air outside.
When the initial sourcing of ‘drier’ air from my ceiling cavity did not work it was reconfigured again to draw air from outside (based on the theory that the outside air was less humid than that inside….but I guess this only holds true if it is not raining or foggy outside). This did not also work with moisture being the continued problem.
The heat exchanger part worked particularly well but the reason I bought this system was primarily to control the moisture within the house, and the heat exchanger was a bonus. I had the DVS and high sales pressured HRV people around, but not one actually asked about the construction of my home, they were just focused on a securing a sale.
I would be interested in hearing if others have had similar experiences with block cavity constructed homes, and what they did to combat moisture other than a dehumidifier.
Thanks
Herb on 10 Jun 2010 at 9:22 pm #
Richard, what area do you live in?
warren on 24 Jun 2010 at 4:34 pm #
Does anyone know where to buy arizona 5 filters not HRV as I don’t like the black mail sales pitch. You ask them how much for filters, first thing they say is your warranty will be void if they dont install at 2 year yeah right smart arses cheers warren alttruck@xtra.co.nz
Kevin on 04 Jul 2010 at 6:21 pm #
Checking out ventilation systems. If I use a HRV it would blow warm air into house, But it would be more humid than the air in my house. House humidity is about 45% in roof space cause it mid winter it is 86%.
So why would I want to replace with more humid air, admittedly it is warmer by a couple of degrees but is much more humid.
Steve Taylor on 05 Jul 2010 at 11:38 am #
The figures seem really odd. Why should the roof space be that humid. If this was the norm roofs would be collapsing all over as the wooden supports would be rotten.
Kevin on 06 Jul 2010 at 3:44 pm #
Hi Steve,
Its a concrete tile house,only about 30 year old.Up top is good dry,no smells at all.Good insulation.Had the roof sealed and treated about 5 years ago.A concrete tile roof house has heaps of air ventilation,my thoughts it would be as humid as outside.
pip rhodes on 08 Jul 2010 at 12:53 pm #
I found this site so useful when trying to decide whether to have a leap of faith and purchase a HRV system. I live in Dunedin and condensation was an issue in the house. The rep was OTT and I think the product is expensive but as far as removing condensation it has been superb. I was never ’sold’ this product as a heating device- but it has raised the temperature by 2 degrees in non heated areas on a cold day- and on sunny days by many more degreees. So overall I am thrilled with the result. It also removes cooking odours.
herb on 15 Jul 2010 at 11:33 pm #
Relative humidity is associated with heat. Heat mobilises moisture in the air and raises the RH.
You heat a home it mobilises the moisture into the air, this is a prime opportunity to flush this moisture laden air out with a good PPV consequently conditioning your home and over time making it drier.
On a cold morning the air inside the home will be cold and the RH will be low. This is a false sense of security regarding moisture in the home. The moisture at that point has settled and or soaked into the home fixtures and furnishings.
You can see the the RH in a home change from 55% RH at 8am to 80%+ RH by 12. Sometimes the RH in the ceiling will be high when it heats up but this is caused due to the condensation formed in the ceiling on a cold night. This moisture mobilises when the ceiling heats up creating a high RH, it is not there for long and soon dissipates as the air in the ceiling is replaced and expands. Once this moisture laden air is gone from the ceiling, any fresh air which is heated will have a much lower RH than outside or what is in the home. It is this drier warmer filtered air which is flushed through a good PPV which helps keep your home drier with an average lower moisture content.
herb on 15 Jul 2010 at 11:38 pm #
There are some good down to earth FAQ’s at the Sayr website:
http://www.sayr.co.nz/FAQs/tabid/30620/Default.aspx
Recent testimonials:
http://www.sayr.co.nz/TESTIMONIALS/tabid/32569/Default.aspx
herb on 15 Jul 2010 at 11:46 pm #
Check out some down to earth FAQs and recent testimonials on a good PPV
www sayr co nz
janie on 18 Jul 2010 at 10:28 am #
Are the upvc double glazed windows here fitted with air vents in the frame as they are in the UK? This does allow some air flow.
Kevin on 22 Jul 2010 at 3:05 pm #
I Have a weather station that reads humidity and temp inside and outside.Cheap as it is ,i think it is fairly accurate.
The lower the temp the higher the humidity,inside and out.Thats what it tells me anyway.
Currntly the outside unit is in ceiling space.It is as humid there or near enough to outside.
So why on earth would you want that air in your house?.A couple of degrees warmer sometimes sure but a lot more moisture in the air?
Kevin on 22 Jul 2010 at 10:56 pm #
Any comments on pellet fires appreciated.I live in christchurch and thinking of getting one.
People say they noisey,i go to showroom quiet as,no worse than heat pump.They say older ones are noisey.
One person said his is 3 years old and sounds like a hellicopter?.How can this be?
Is it just because they need maintenance( bearing etc).That maintenance never done?.After all you need to service a heat pump regularly,I never done mine.
Steve Taylor on 23 Jul 2010 at 12:38 pm #
The ones I saw have a constant tinkling sound as the pellets are dropped in. Having had an open fire in my childhood and almost jumping out of my skin when a log has let out an almighty crack they are not too bad. Our heat pump is quite loud, but as it is a constant drone in the background you tend to forget about it.
At the showroom ask them to turn it up to full and see what they sound like when working at their hardest.
herb on 28 Jul 2010 at 3:37 pm #
Kevin. You need to be monitoring the RH in the ceiling on a constant basis and see what it averages at over various times/temps/conditions.
Also you need to be reading the RH inside the house when it is warm, thats where the problems come from with damp homes. Again, if you are reading gauges you need to be extremely thorough in recording and calculating data. It is too easy to be mislead with a couple of readings and making ill informed or uneducated conclusions.
Reiko on 01 Aug 2010 at 6:57 pm #
I’m not sure what the sales people told my parents; i just know that despite the fact i agree it’s somewhat false advertising? It half works for people that have asthma; we’ve seen significant amount of reduction in molds (sorry i spell it without the U, i’m american
) – and other condensation problems. I think the new housing idea is not sound, cause you also gotta look at the city you live in.
Any true person would know that Central Heating, PLUS one of these Heat Recoveries, and maybe the other bits would make it ideal – BUT because we all live in New zealand, it’s enough just running a fan heater to cause a 400 dollar power bill.
Being that i have mild to severe asthma depending on the time of year and the allergic issues i have, the HRV has even made living with a dog (which we all know that asthmatics SHOULDNT have long haired shedding adorable horse-like puppies whom slobber on you at ever chance! XD) more tolerable.
Yes; i think there’s things that every system goes wrong with- i just know that what we have (Yes a branded HRV, which may or may not be true to it’s form) works as well as it can. Burnt Toast in our house because it’s SMALL, works over a period of time.. and frankly it doesnt serve when you leave your bathroom door open to serve the house the nasty smells after someone’s been eating curry. (So burnt toast mode is totally not going to fix that
)
All in all i think the one we have may not BE the best, but it works for what we paid for it, without spending an arm and a leg on power that is.
Matt on 17 Aug 2010 at 1:15 pm #
@ janie 18 July: Hi Janie. I’m not sure about the uPVC window manufacturers, but some of the aluminium fabricators can include trickle ventilation in the frames.
Our company – Easy Air – has been manufacturing and supplying glazed-in trickle (passive) vents for the last 13 years. Our vents can be fitted in to new windows (we also have a double glazed model), and they’re the only ones on the market here that can also be retro-fitted into existing windows.
Trickle vents are standard in the UK, and are very effective at controlling moisture levels.
Positive Pressure Ventilation is not common over there. In fact it’s not even recommended in the building regulations, whereas passive is.
Matt on 17 Aug 2010 at 1:32 pm #
@ Kevin: Hi Kevin. Great idea setting up a humidity meter in your home before making any decision on which ventilation to choose. I’m surprised more people don’t do that, along with taking temperature readings in their roof space before selecting a ventilation option.
A quick note on Relative humidity vs total humidity. Cold air has the capacity to hold much less water vapour than warm air. Relative humidity is the measure of the actual water vapour RELATIVE to the capacity of the air to hold water AT THAT TEMPERATURE.
So, cold air with a high RH%, will actually have less moisture than warm air with a lower RH%.
As an example: If you draw in 10C outside air with 80% RH (approx. 7.2 g/m3 of water) and warm it to 20C, the RH of that air has now dropped to approx. 42%RH.
So you can see that drawing in cooler air and warming it, at the same time displacing the old damp inside air continually will lower your total levels of water vapour.
Hence the standard recommendation to continually replace inside air with fresh outside air.
I hope that helps
J Conner on 27 Aug 2010 at 2:40 pm #
I first heard of Sayr when researching opinions in these type of forums. I got one and now it’s my turn to give them a plug. They’re a smaller coy for sure but have proven themselves equal and surpassing the big boys as far as I’m concerned. More than matched them in features and result. Well done guys, I’m telling others like I said I would.