HRV Sales Methods

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#451143 23-Mar-2011 15:11

Handle9:
mattwnz:
Handle9:
mattwnz:

I would suggest you ask an architect what their opinion is on these types of systems. I haven't seen any scientific research on them and how effective they are.

Honestly most architects don't have a clue about mechanical systems (ie ventilation, heating etc). Generally what the care about is what the wall controllers and the diffusers look like - not how or why they do or don't work.

That is a sweeping statement. If you get a good experience one who knows their stuff, they will know a lot about ventialltion and the best options. I well designed house can hve natural ventialltion using the 'stack effect' and passive solor heating and cooling, which can do away with the need for such ventialltion systems anyway. These ventilation systems that you install are generally a sticking plaster solution for poorly designed and insulated houses, which make up the bulk of NZs housing stick.

I don't install them, I don't sell them. I work in the industry and have a pretty good knowledge of how they work.

My statement is based around experience of dealing with architects who don't know what they are talking about with regards to these systems. It's not what they do - it's mechanical services engineers who are trained to design mechanical systems. Some architects have knowledge of mechanical systems but if you want to talk to an expert talk to an expert - a mechanical services engineer not an architect.

My parents do have one of these sorts of systems installed about 15 years ago, although not the brand being discussed here.. One thing that does concern me about the ones that suck air from the roof space, is that just below the input fan are fibre glass batts. These glass particles in the batts are tiny, and I would doubt the filter, which just appears to be a white fibre sheet, would stop these particles from getting sucked through it and into the rooms.

timmmay

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#451147 23-Mar-2011 15:17

I have a small ceiling ventilation system, it was in the house when I bought it, not sure which brand one of the smaller ones. It only has outlets in the hallway and the kitchen. In winter on sunny days it brings warm air into the house quite well, and makes it a few degrees warmer. I turn it off at night anyway because the motor noise annoys me, plus it'd be bringing cold air in.

If I replaced it now i'd get a quieter system that has a heat exchanger, my pick is Cleanaire - I have no association with them, they just seemed like a good system when I was researching a couple of years back

http://www.cleanaire.co.nz

I talked to one of the major HRV/DVS vendors, I forget which one. The salesman was pushy and couldn't answer my questions (i'm an engineer). I sent him packing and from memory I complained to the manager of the store that he didn't know what he was talking about.

The cleanaire guy I spoke with was quite knowledgeable, not a salesman but more an engineer type.

gzt

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#451150 23-Mar-2011 15:30

timmmay: These glass particles in the batts are tiny, and I would doubt the filter, which just appears to be a white fibre sheet, would stop these particles from getting sucked through it and into the rooms.

Indeed. On top of that, it is worth remembering for all systems, regular and scheduled filter replacement is a must.

Handle9

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#451154 23-Mar-2011 15:49

gzt:
timmmay: These glass particles in the batts are tiny, and I would doubt the filter, which just appears to be a white fibre sheet, would stop these particles from getting sucked through it and into the rooms.

Indeed. On top of that, it is worth remembering for all systems, regular and scheduled filter replacement is a must.

Definitely. Also you can buy different grades of filters. If you get a finer grade you pay more but it lets far less particulate through.

timmmay

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#451156 23-Mar-2011 15:56

The filter on mine is a big white sock. By the time I replaced it, it looked like a big black sock.

The Cleanaire systems have nice filters, different grades, etc. The one I have I don't know anything about, but I should maybe wash it next time i'm up in the ceiling.

Shock

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#451193 23-Mar-2011 18:38

Handle9:
Honestly I think you're a little confused. Smartvent is a positive pressure system. Securimax and DVS do do heat exchanger systems which is what you're referring to but their entry level systems are PPV.

Right yes that makes sense. I am referring to the Synergy & DVS heat exchanger systems not the PPV versions.

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Skolink

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#451224 23-Mar-2011 20:43

Handle9:
They're pretty crap with heatpumps unless you have very well insulated ducts and short runs. The're much better with fires as fires don't modulate their outputs and are usually oversized and overheat the space. That means you've got enough spare heating capacity to afford losses through a cold ceiling space.

Also the heat from a fire is stratified - very hot by the ceiling where the duct intake is, cooler lower down. Heatpumps mix the air to an even temperature.

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Skolink

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#451228 23-Mar-2011 20:49

mattwnz:
I haven't seen any scientific research on them and how effective they are.

I have, they are crap. See:
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
Have seen other research by an energy efficiency consultant from Dunedin, and he came to the conclusion there was no free heat in ceiling spaces (unless you are running a sauna in summer).

richms

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#451243 23-Mar-2011 21:40

Mum has one, gets hot smelly air coming in on hot days, and cold smelly air on cold days, there is no time at all in the winter that the roof is above the house temperature before everyone has gone for the day, and when everyone is back, it has undone whatever good it may have done with the cold smelly air. you can turn it off for a while, but it comes back on again.

The installers put the vents directly infront of alarm sensors in 2 rooms, and when it was installed there was an unducted bathroom fan about 3m from the inlet, which is hanging about 1m above the batts. as heat rises I would have thought it would be useful to have it up 5m or so at the peak of the roof.

Only useful thing IMO to come out of it was the installation of a power socket in the roofspace so I can plug the server into.

Richard rich.ms

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#451271 23-Mar-2011 22:47

We got a Smartvent PPV system installed a couple of years ago, our house is fairly well sealed (about 10 years old) and we used to suffer from pretty bad condensation. Condensation is no longer a problem!

Ours was installed with the heat transfer option, as we have a log burner and our house already had an existing heat transfer system. The old heat transfer system was removed and now the Smartvent does both functions automatically. So we have improved our heat transfer setup and removed condensation.

One thing that did annoy me, which has been mentioned by multiple posters above, is that fact that the unit will suck in cold air in the winter. Current Smartvent systems now have a function to turn the fan off completely when the temperature drops below a certain level. Ours didn't have this feature, but I checked with Securimax and it was simply a case of sending the control panel up to them for a firmware upgrade, which I did. The fee was around $100 for this but it was a feature that I simply had to have so I didn't mind paying.

We went with Smartvent because they are sold, installed and serviced by electricians, so no sales people involved. I was also impressed with their features and how they have actually designed a true heat transfer function. There was also the advantage that you'll probably pay less for filters as you can just pop down to your local electrical wholesaler and buy them there.

We had a DVS guy in, he was about 50% more expensive than Smartvent for an equivalent system and their attempt at a heat transfer system was laughable - basically another inlet fan on a thermostat piped into the DVS ducting. Also he was just a sales guy, so really didn't have much of a clue... I don't even recall him looking in the ceiling space.

Today, if I was going to do it all again, I would install a true heat recovery system (a system with a heat exchanger). Hopefully the cost of these has come down - I did price a Smartvent Synergy system at the time when I was looking and it was over the $10k mark. DVS had just launched a similar system at the time and it was over the $12k mark from memory. Just couldn't justify that at the time.

TL;DR - I swear by Smartvent PPV as it works in my situation, but if you can afford it go with a true heat recovery system.

richms

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#451273 23-Mar-2011 22:58

Condensation is a symptom of having crap glazing, not having a dampness problem. IME the dryness needed to keep single glazed windows condensation free when it is freezing outside and 22-24 degrees inside is so dry that its not healthy.

You can go pushing your heated air out to replace with dryer unheated air, I will stick to a dehumidifier which doesnt cause a heat loss like a PPV does. Set it to 75%, leave it once it has a drain pipe put thru.

Richard rich.ms

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#451338 24-Mar-2011 09:44

There seems to be a surprising number of experts here who seem to dismiss particular solutions with little first-hand knowledge of them. If you are looking to purchase one of these types of units then I'd recommend asking friends and family. That's the best way to gauge how good they are - ask people you know and trust who have owned them for a while. You just don't know if posters in these forums have a vested interest in a particular solution and therefore will try to discredit the competition.

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Jaxson

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#451341 24-Mar-2011 09:58

As mentioned above, it's usually warm moisture laden air touching cold single glazed glass that causes the condensation. If you pump cold air into your house over night that will cool the air in your house, bringing it closer to the cold temperature of the windows. And wow, no more condensation....

mattwnz

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#451476 24-Mar-2011 14:50

richms: Condensation is a symptom of having crap glazing, not having a dampness problem. IME the dryness needed to keep single glazed windows condensation free when it is freezing outside and 22-24 degrees inside is so dry that its not healthy.

You can go pushing your heated air out to replace with dryer unheated air, I will stick to a dehumidifier which doesnt cause a heat loss like a PPV does. Set it to 75%, leave it once it has a drain pipe put thru.

Or uninsulated walls. Many of NZs houses have no insulation in the walls and sometimes none in the roof either, and you can get water running down the walls and mould growth. Insulation should be installed before anything else, and double or triple glazing is also an idea. If getting new glazing, you need a thermal isolating bridge on the window frame.

timmmay

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#451480 24-Mar-2011 14:59

I've done a lot of work to my house since I bought it. I insulated the ceiling (a LOT), walls (foam pumped in), and under the floor (5cm thick batts like pads), as well as having a ground sheet put down. That made a big difference to the temperature, and the ground sheet made the place less damp and better smelling. Heat is retained a lot better than it used to be, and it's a really, really old house, but reasonably well sealed.

Next I put in a heat pump. That made a HUGE difference to the comfort levels.

I still had condensation, as expected. The peak power bill in winter dropped from $500/month to about $350/month, and instead of being 10 degrees inside it's 18 degrees in the morning and again in the evening.

Next I put in retrofit double glazing, one of the "magnetic" ones. Magnetite. Great product, the Wellington installers are a bunch of clowns, but i've spoken with people in other areas and those installers sound much better. This step virtually eliminated condensation on the windows. On the coldest days instead of a pool of water on my window sills I have a light mist on the new interior plastic.

My next step is to replace the little ventilation system that goes into two rooms with a heat recovery ventilation system that goes into each room. It's only about $5K max, i'll get around to it eventually. I don't like them at night and that's one of the times they're most valuable, so no rush.

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