HRV vs DVS vs Moisture Master

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CYaBro

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#391092 12-Oct-2010 21:41

I've spoken to one guy, who is a bit of an expert in this area, and he couldn't understand why anyone would want one of these types of systems.
Why suck dirty air from your ceiling space into your house? Yes they have filters but the best filter is your lungs. These sorts of systems are being banned in some US states too he said.

He said a heat exchange system is the way to go. Suck fresh air in from outside, use a heat exchanger to transfer the heat from the air in the ceiling to the fresh air and then pump that into the house.

This was one of the systems they suggested to look at instead:
http://www.cleanaire.co.nz/
And no he doesn't work for them!

Opinions are my own and not the views of my employer.

jaymz

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#391103 12-Oct-2010 22:14

robbyp:

That isn't what the explaination was from the expert. The guy explained that the damp air in the subfloor space, was getting drawn up through the wall cavities by the ventiallation system, into the roofspace, and then was being pumbed back into the house. They were then trying to solve this by installing polythene into the subfloor, and to dig drains around the property as it was low down. The rising damp he talked about, was something different, as the bricks should never be in direct contact with the soil, and that would be a construction fault. There should be DPM between the foundation wall bricks and the soil. It was possibly a combination of both that was causing problems, but it was made worse by the system installed.

I disagree somewhat with that.

The reason why the HRV made it worse was because it blew moist air into the house.

The moist air was caused by a damp roof space.

The damp roof space was caused by rising damp.

The damp was caused by a badly designed section (house lower than the rest of the section).

There is no way it would suck water up walls (unless it had one hell of a fan unit in it)

That was my point, i was only clarifying what was said on the show.

robbyp

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#391110 12-Oct-2010 22:30

jaymz:
robbyp:

That isn't what the explaination was from the expert. The guy explained that the damp air in the subfloor space, was getting drawn up through the wall cavities by the ventiallation system, into the roofspace, and then was being pumbed back into the house. They were then trying to solve this by installing polythene into the subfloor, and to dig drains around the property as it was low down. The rising damp he talked about, was something different, as the bricks should never be in direct contact with the soil, and that would be a construction fault. There should be DPM between the foundation wall bricks and the soil. It was possibly a combination of both that was causing problems, but it was made worse by the system installed.

I disagree somewhat with that.

The reason why the HRV made it worse was because it blew moist air into the house.

The moist air was caused by a damp roof space.

The damp roof space was caused by rising damp.

The damp was caused by a badly designed section (house lower than the rest of the section).

There is no way it would suck water up walls (unless it had one hell of a fan unit in it)

That was my point, i was only clarifying what was said on the show.

I don't dispute that, but raising damp will only go so far up the wall, and that would have existed before they installed it. Normally there is DPC between the wall framing and the foundations, to prevent that rising damp, and it would only go a certain way up the wall. If it was bad, there would be rotting of the framework, and potentially leaking building problems.

The problem was that the TV show showed that the ventialltion system made the house damper, and turning it off reduced it. The ventialltion system could potentially suck up air through the wall cavity, as they are hollow, with only a top and bottom plate and some dwangs in between the roof and the subfloor. You do also have holes in the wall framing for wires and pipes. It depends on how sealed the roof is from outside, so to how much air was draw up through the walls.

pukster

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#391264 13-Oct-2010 11:25

hey guys thanks for all the input ,my mind is made up ,as hrv are crap ,moisture master do everything above including pulling air in from outside if you wish and they do a heat pump on the system straight into your rooms if need be so far cheaper on power ,i also read that they do warn you of damp rising if you dont have poly under the house so at least they are aware of this ,good show target thanks for the heads up ,i wouldnt have watched it otherwise

Jaxson

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#391273 13-Oct-2010 11:43

Seriously though, do a thurough audit prior to installation to determine where your dampness may be coming from. I think if anything that should be the moral of the story and this applies directly to the target episode as well.

If your mind is made up then that's fine too, but as has previously been mentioned, check the other threads for a massive amount of pratical information on most of the common moisture causes. If you don't spend the time doing this, you won't get the best out of your house, or any solution system you install either for that matter.

Nety

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#391307 13-Oct-2010 12:48

Jaxson: Seiously though, do a thurough audit prior to installation to determine where your dampness may be coming from. I think if anything that should be the moral of the story and this applies directly to the target episode as well.

If your mind is made up then that's fine too, but as has previously been mentioned, check the other threads for a massive amount of pratical information on most of the common moisture causes. If you don't spend the time doing this, you won't get the best out of your house, or any solution system you install either for that matter.

+1 Most sources of damp can be controlled ie. extractor over a stove. This should always be the first option. If you do everything practical and still have a problem THEN look at one of these products.

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robbyp

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#391326 13-Oct-2010 13:50

Nety:
Jaxson: Seiously though, do a thurough audit prior to installation to determine where your dampness may be coming from. I think if anything that should be the moral of the story and this applies directly to the target episode as well.

If your mind is made up then that's fine too, but as has previously been mentioned, check the other threads for a massive amount of pratical information on most of the common moisture causes. If you don't spend the time doing this, you won't get the best out of your house, or any solution system you install either for that matter.

+1 Most sources of damp can be controlled ie. extractor over a stove. This should always be the first option. If you do everything practical and still have a problem THEN look at one of these products.

Actually one of the main source of dampness in a house is people breathing. Thats why you get a lot of condsation on bedroom windows in the moring. Keeping your bedroom door open at night can help a lot with condenstion.

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Nety

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#391380 13-Oct-2010 16:00

robbyp:

Actually one of the main source of dampness in a house is people breathing. Thats why you get a lot of condsation on bedroom windows in the moring. Keeping your bedroom door open at night can help a lot with condenstion.

Approx 0.2 L per person per hour awake, down to 0.02 ppph asleep so not a huge amount but definitely a sizable part of the problem

. There is no way you can completely remove all sources of moisture but managing them will make a huge difference.

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