Home Ventilation - Separating the Salient from the Sales

Forums › Home Workshop DIY › Home Ventilation - Separating the Salient from the Sales - Your thoughts?

Slumlord

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Topic # 119316 28-May-2013 10:02

Anyone got some sound insight on home ventilation? Lots of companies out there, lots of sales talk. I am comparing Sayr and Smartvent. HRV seems to expensive and pushy. Wondered if anyone could help with separating the companies, if speaking from experience. Does a fancy controller really matter? Is it all about the number of thermostats? As far as I can see they all do the same thing. Thoughts, people? PS: Don't just tell me to open a window - thanks.

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Vocus

Reply # 826829 28-May-2013 10:13

PPV = all pretty much the same. It mostly comes down to the quality of the components.

Note that you still need to heat your house somehow, no ventilation system drawing in roof or outside air is going to heat your home in winter, unless it actually has a heater built in (although HRV salespeople will swear black and blue that they do).

Slumlord

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Reply # 826831 28-May-2013 10:17

Thanks. Yep, I only need ventilation - trying to prevent condensation and moisture build-up. Not worried about heating.

geekiegeek

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Reply # 826851 28-May-2013 10:45

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we went with DVS in the end but only looked at HRV and DVS. Like you we found HRV to be to pushy. Agree with previous posts that they are all the same. Just get one from a company with a good reputation and warranty I would say.

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hangon

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Reply # 826873 28-May-2013 11:16

positive pressure is not all that helpful during winter.

if i'm building new, i'd get a balanced ventilation system with a heat recovery exchanger, problem is they tend to be expensive and requires good design and installation for the specific house. most houses showcased in "grand design" or "green(?) homes" have one.

but for majority of NZ houses, beef up insulation, install one or more heatpump (you'll probably need one with or without a ventilation system), open windows during daytime, use extractor fan when cooking/taking shower, and maybe use one or more dehumidifier, would work just fine, and probably cost less.

Handsomedan

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Reply # 826885 28-May-2013 11:24

We have one of the older HRV systems and find it good for keeping the house drier and easier to heat.

Like others, they are pushy with the sale, but they're also terrible with after-sales service.

They're suppose to call us to arrange a new set of filters (at our cost) every couole of years. We always have to call them, despite having several calls a months trying to sell us a system that we already have ("sorry - different department").

They're all much of a muchness. But they all do what you want, which is to assist with removing moisture.

Good luck!

Handsome Dan Has Spoken.

timmmay

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Reply # 826890 28-May-2013 11:36

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Look at Cleanaire, I think they're in Chch. They do a heat recovery ventilation unit that minimises wasted heat. Their prices and technology were good when I last looked, and when I get around to replacing my cheap old system that's what I'd use.

Ideally you want integrated heating and ventilation. There's no point pumping cold air inside in winter and hot air in summer. Mitsubishi Lossnay I think can do integrated heating and ventilation.

I have a cheap two outlet system, put in by a previous owner. What I do is run the ventilation system between 7am and 11am in summer, so it doesn't get too hot. In winter I run from 9am to 3pm, to try to get any free heat I can. I never run it in the evening, as it's just pumping cool air in, and it makes a noise. I may in future set it to come on for 5 minutes an hour if the house gets stuffy, but haven't needed to so far. I use a $10 timer from bunnings.

Ventilation gets rid of water in the air, making it easier to heat your home. It DOES NOT heat your home, unless it happens to capture some warm air from the ceiling cavity heated by the sun. That does happen quite often on sunny days, but on cold days it will cool your house.

If you just want to get rid of condensation get some retrofit double glazing - it was very effective for me. A ventilation system running 24/7 with outlets in every room will reduce condensation but won't eliminate it, and it'll make the house cold. Remember ventilation means cutting holes in your ceiling, which also lets heat out whether or not the system is running.

I suggest more research is require, rather than just bunging in a ventilation system. Perhaps even consult a heating engineer, or use a good company and tell them your aims, not what you think you need.

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Jeeves

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Reply # 826903 28-May-2013 12:03

PPV, or positive pressure ventilation systems, IMHO, arn't suitable for NZ climate and houses. These are the systems which take air from a ceiling cavity, and force it into the rooms. Stale air is then 'pushed' out of gaps and doors/windows to create a bit of flow through the house.

As mentioned previously, these do nothing to heat your house directly.
The problem with NZ houses is A) Damp, B) insulation.
Older houses tend to be poorly insulated. This makes them cold, and so people shut all the doors and windows to try and keep the heat in. They go about their daily business, breathing, boiling the kettle, drying clothes, having showers, doing the dishes, and cooking. All of these activies create moisture.
Because the house is shut up, all this moisture increases the relative humidity of the air inside the house. The air gets wetter, in other words.
Because of the poor insulation, a lot of interior surfaces like windows, and the inside of external walls, remain cold due to the outside temperature. This causes moisture to form on them due to condensation (Much like a cold coke can on a humid summers day). This moisture gets absorbed by these surfaces and wammo, you have mold and a cold damp house. Air that has higher relative humidity takes a lot more energy to heat as well.

Typically, during winter, the relative humidity of outside air is a lot lower than inside a house. This is where PPV comes in. It brings in this outside air (Because the roof cavity is mostly made up of outside air), and puts it inside. Because it's a bit drier - it can dry out surfaces and make it easier to heat. But of course, it's bringing in all this cold air! They rely on the intake being in the highest part of the building to try and recover some heat - which often is useless because roof cavities are so draughty.

A heat recovery system with an integrated heat exchanger is a lot more ideal. That cleanaire outfit that timmay mentioned are the best that I have found so far.
These systems suck the warm air from warm rooms like your lounge, and pass it through a heat exchanger. This exchanger takes the heat from this air and puts it into fresh air that is drawn from outside. This outside air is then pumped into bedrooms and the like. Whilst you will still lose a little heat from this process - it is considerably better than a PPV. So now you have warm, dry (Low humidty) air coming into your house - much more comfy!

Again, you will still need a heat source for this system (Fireplace/heatpump) - but they are miles better than a PPV system. Slightly more pricey - and they need a bit more room in your cavity - but certainly worth it.

Source: I'm a Data Center engineer, so have a bit of exp in air flow and humidity management.

mrdrifter

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Reply # 826908 28-May-2013 12:11

I would say the HRV people must be very pushy, the place we are in at the moment has a full on system installed, but the roof space available for it to draw from negates any possible usefulness. The money would have been much better spent on better insulation and heating throughout and then simple ventilation for places like the bathrooms and Laundry.

jonherries

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Reply # 826913 28-May-2013 12:17

Jeeves: PPV, or positive pressure ventilation systems, IMHO, arn't suitable for NZ climate and houses. These are the systems which take air from a ceiling cavity, and force it into the rooms. Stale air is then 'pushed' out of gaps and doors/windows to create a bit of flow through the house.

As mentioned previously, these do nothing to heat your house directly.
The problem with NZ houses is A) Damp, B) insulation.
Older houses tend to be poorly insulated. This makes them cold, and so people shut all the doors and windows to try and keep the heat in. They go about their daily business, breathing, boiling the kettle, drying clothes, having showers, doing the dishes, and cooking. All of these activies create moisture.
Because the house is shut up, all this moisture increases the relative humidity of the air inside the house. The air gets wetter, in other words.
Because of the poor insulation, a lot of interior surfaces like windows, and the inside of external walls, remain cold due to the outside temperature. This causes moisture to form on them due to condensation (Much like a cold coke can on a humid summers day). This moisture gets absorbed by these surfaces and wammo, you have mold and a cold damp house. Air that has higher relative humidity takes a lot more energy to heat as well.

Typically, during winter, the relative humidity of outside air is a lot lower than inside a house. This is where PPV comes in. It brings in this outside air (Because the roof cavity is mostly made up of outside air), and puts it inside. Because it's a bit drier - it can dry out surfaces and make it easier to heat. But of course, it's bringing in all this cold air! They rely on the intake being in the highest part of the building to try and recover some heat - which often is useless because roof cavities are so draughty.

A heat recovery system with an integrated heat exchanger is a lot more ideal. That cleanaire outfit that timmay mentioned are the best that I have found so far.
These systems suck the warm air from warm rooms like your lounge, and pass it through a heat exchanger. This exchanger takes the heat from this air and puts it into fresh air that is drawn from outside. This outside air is then pumped into bedrooms and the like. Whilst you will still lose a little heat from this process - it is considerably better than a PPV. So now you have warm, dry (Low humidty) air coming into your house - much more comfy!

Again, you will still need a heat source for this system (Fireplace/heatpump) - but they are miles better than a PPV system. Slightly more pricey - and they need a bit more room in your cavity - but certainly worth it.

Source: I'm a Data Center engineer, so have a bit of exp in air flow and humidity management.

Totally agree. The principles you need to remember are:

Inside air is generally more humid and warmer. Getting rid of the humidity and keeping the heat is what you ideally want to do to reduce condensation and mould (effects of a warm damp environmentt).

A positive pressure system assumes that roof air is drier and warmer than in the house. Generally they won't run when it is cold which is when condensation is worst, and if they do, they push your moist air out with the heat, meaning you need to reheat the dry air.

Keeping the heat and getting rid of the moisture is what you should be doing ideally, this is what a balanced ventilation system does. Bear in mind that it is more expensive, but you won't need to spend as much on heating as you reclaim a lot of the heat.

You might find that better insulation and extractors in the bathroom and kitchen is a cheaper solution, but certainly still not a better solution (same problem of throwing the heat away with the humidity).

Jon

jonherries

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Reply # 826916 28-May-2013 12:21

Thought I would just add, I have been planning a balanced ventilation system to replace our PPV one.

Would people recommend I put the inside air intakes in the bathroom, on the end of the clothes drier and above the oven as these are good sources of humid/hot air (I would have a few others as well).

Presumably those sources (esp. oven and drier) will hammer the filter?

Jon

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Reply # 826917 28-May-2013 12:21

anyone know how to get off the HRV system? We still get called about monthly despite making VERY clear in no uncertain terms we would never buy anything from them.

vexxxboy

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Reply # 826920 28-May-2013 12:30

networkn: anyone know how to get off the HRV system? We still get called about monthly despite making VERY clear in no uncertain terms we would never buy anything from them.

it took 5 cold calls and me becoming ruder and ruder before they stopped calling me. The dont like no for an answer

Common sense is not as common as you think.

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Reply # 826921 28-May-2013 12:30

jonherries: Thought I would just add, I have been planning a balanced ventilation system to replace our PPV one.

Would people recommend I put the inside air intakes in the bathroom, on the end of the clothes drier and above the oven as these are good sources of humid/hot air (I would have a few others as well).

Presumably those sources (esp. oven and drier) will hammer the filter?

Interesting question! Think about summer as well as winter, extra heat in the system in summer would be a bad thing, so it'd have to be switchable. However in winter yeah it could give you a big boost to have clothes drier exhaust and shower steam.

networkn: anyone know how to get off the HRV system? We still get called about monthly despite making VERY clear in no uncertain terms we would never buy anything from them.

Try the do not call list. Or get rid of your home phone - I haven't had marketing calls since I switched entirely to cell.

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jonherries

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Reply # 826930 28-May-2013 12:50

timmmay:
Interesting question! Think about summer as well as winter, extra heat in the system in summer would be a bad thing, so it'd have to be switchable. However in winter yeah it could give you a big boost to have clothes drier exhaust and shower steam.

Haha hadn't thought of summer, although you can have switchable zone dampers, so you could dump the heat based on some temp sensors?

Jon

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Reply # 826959 28-May-2013 12:56

I was looking for thermostat controlled inputs a while back, that would open a valve to take warm air from my lounge if the heating was on, but not if it wasn't. I never found anything suitable though.

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