New DVS EC Climate Control

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kiwifidget

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#319619 14-May-2025 08:05

Our old DVS3 pooped itself a while ago, so we havent had it running for nearly a year.

Finally got the newer EC Climate Control upgrade installed a couple of weeks ago.

The settings are a bit weird to manage.

We have set the DVS for 22C, but it never gets to that.

I have noticed the house feels considerably colder, even on a fine day.

It doesnt report humidity, but my Tapo sensors do, and they are all saying 60-70% relative humidity.

And my clothes in the wardrobe, feel cold and damp.

What would be an acceptable humidity level in a house only 15 years old with double glazing?

In Pukekohe, coz now we are in the SuperCity we get their stink humidity 😀

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#3372992 14-May-2025 10:12

a lot to unpack here. what would be helpful is to know what the outdoor tem/humidity is and what the indoor temp humidity is. keeping track of both and what the unit is doing.

ideally find the install manual.

We have set the DVS for 22C, but it never gets to that. whats the ceiling temp its reporting? otherwise turn your heating on, its a ventilation system not a heating system.

What would be an acceptable humidity level in a house only 15 years old with double glazing? its got nothing to do with the house but rather what the humidity outside is. RH of course will change with the temp. heating up the house will reduce the RH. for auckland 60-70% is pretty good.

you have to remember that the ventilation system, as well as the ton of air leakage, will bring in outdoor humidity. the dvs ventilation system will slow down or speed up (depending on how its set) based on humidity. i don't know if its based on simple RH or takes the temp into account as well.

freitasm

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#3372996 14-May-2025 11:11

tweake:

you have to remember that the ventilation system, as well as the ton of air leakage, will bring in outdoor humidity. the dvs ventilation system will slow down or speed up (depending on how its set) based on humidity. i don't know if its based on simple RH or takes the temp into account as well.

As per their page: "DVS Positive Pressure Ventilation Systems use ‘positive pressure’ technology to push the stale, moisture-laden air out of your home, and replace it with drier, fresher, filtered air from the roof space,  or outside the house."

So on a very cold and humid day (Wellington winter), it basically brings that cold and humidity inside the house. In summer you can just keep the doors and windows open.

At face value it would make indoors damp and cold, requiring additional heating and dehumidification. Condensation on single layer windows would be natural in this condition.

So, really, what's the DVS value here?

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#3373010 14-May-2025 11:53

To echo Mauricio's point, when we bought our house in Auckland after moving from the UK, I invited some heat pump installers and a HRV salesman to visit and tell me about their products. The HRV man pulled up in his flashy ute and proceeded to tell me I didn't really need heating because there was all this nice warm clean air in the attic ready to be pumped into the house. When I showed him the display of the wireless thermometer I had installed in the attic, which read 12C on that winter morning, and asked how pumping that air into my house would help, he was a bit lost for words.

We went on to install three heat pumps in the house and open windows as required to let fresh air in. I remain convinced that positive pressure systems are largely snake oil.

freitasm

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#3373011 14-May-2025 11:54

As above.

tweake

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#3373018 14-May-2025 12:11

freitasm:

As per their page: "DVS Positive Pressure Ventilation Systems use ‘positive pressure’ technology to push the stale, moisture-laden air out of your home, and replace it with drier, fresher, filtered air from the roof space,  or outside the house."

So on a very cold and humid day (Wellington winter), it basically brings that cold and humidity inside the house. In summer you can just keep the doors and windows open.

At face value it would make indoors damp and cold, requiring additional heating and dehumidification. Condensation on single layer windows would be natural in this condition.

So, really, what's the DVS value here?

actually auckland/northland is worse, which is why auckland/northland have the bulk of the moldy homes.

the value is ventilation. every home needs ventilation for health reasons. i've done the windows thing and its not good. relying on weather is a poor way of doing it. ventilation systems are more consistent, you get airflow when there is no wind, get less airflow when there is strong wind (compared to open windows). plus you no longer need to open windows (security). also its filtered air, so its cleaner. less pollen/dirt flies mozzies etc.

yes your still going to get the same cold humid air as you normally would. heating/dehumidification is as per normal. you might get a slight gain due to ceiling temp being a tad warmer, but its not "heating". plus you get air movement which helps dry the house. eg wet clothes will dry even on a poor day as long as you have wind/airflow.

the catch, in humid areas you want to make sure you do not have excessive airflow as it pulls in more humidity. i turned my ventilation system down and it made the house drier.

ventilation systems with humidity control can do things a few ways. one is to slow the fan down when there is higher outdoor humidity (eg it just rained) or increase the fan speed when there is higher indoor humidity (because there is more people etc). how well it works depends on if its based on just RH or calcs dew points (ie factors in the temps as well as the humidity). but its never going to lower the absolute humidity below that of outside. it doesn't provide separation (like an erv does) and its not a dehumidifying system. your house will still be dictated by the weather and your own heating/dehumidification.

tweake

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#3373021 14-May-2025 12:14

shk292:

To echo Mauricio's point, when we bought our house in Auckland after moving from the UK, I invited some heat pump installers and a HRV salesman to visit and tell me about their products. The HRV man pulled up in his flashy ute and proceeded to tell me I didn't really need heating because there was all this nice warm clean air in the attic ready to be pumped into the house. When I showed him the display of the wireless thermometer I had installed in the attic, which read 12C on that winter morning, and asked how pumping that air into my house would help, he was a bit lost for words.

We went on to install three heat pumps in the house and open windows as required to let fresh air in. I remain convinced that positive pressure systems are largely snake oil.

HRV are well known for their bs sales pitch and high prices.

positive pressure systems work well, far better than open windows (see above) but they are often way overpriced.

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#3373045 14-May-2025 13:48

I had HRV visit years ago, they were full of it. Positive pressure has some value, we have a single outlet near the ducted heating system that we turn on and off with automation so each room gets fresh air. It moves a lot more air than opening windows. We also have HEPA and charcoal or carbon filters on the PPV system, so the air is cleaner than from windows.

In winter the outside air is often high relative humidity but low absolute humidity. Air that's 10 degrees 90% humidity when heated to 22 degrees might be 50% humidity. I have a home assistant extension that does the calculations for me, based on the temperature and absolute humidity I turn PPV systems on and off.

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openmedia

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#3373108 14-May-2025 16:19

We had a DVS system 25 years ago in our first NZ house. It was an older style house with an iron roof that gathered a lot of heat, but we added the heat transfer system for winter use to re-distribute heat from the wood burner.

Overall we were very pleased as it removed the damp from the house and took the edge off our bedrooms in winter. In part this was because the thermostat was set so we didn't pull cold air from the roof in winter below a certain temperature.

In our current more modern house we've focused on heat pumps.

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freitasm

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#3373113 14-May-2025 16:45

@openmedia how can heatpumps help with humid interiors? Just using Heat won't dry. We tried with the DRY option but that's basically blasting cold air.

kiwifidget

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#3373114 14-May-2025 16:46

All very good points. Thank you.

We have turned the fan down, that has certainly helped.

Good to know that 60-70% RH is not the end of the world. It was not something we could monitor or control before so its a new thing to worry about.

Chur!

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tweake

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#3373115 14-May-2025 16:51

kiwifidget:

Good to know that 60-70% RH is not the end of the world.

rule of thumb is above 80% is mold territory (however there is more to it). best for health is in the 40-60% range.

tweake

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#3373119 14-May-2025 17:02

freitasm:

how can heatpumps help with humid interiors?

the only real way they can do it is to heat up cold air. heating helps a lot with keeping houses dry.

dry mode is an inefficient way to dehumidify the air. a dehumidifier will work, however it need to be big and costly to run in most nz homes as they leak way to much air. this is where air tight homes comes into play and you use an erv for ventilation to provide separation from outdoors. the erv keeps most of the outdoor humidity out so the dehumidifier only has to handle the humidity the people make in the home. having the erv means you can run a much smaller dehumidifier and be a lot cheaper. the bonus is the heat from the dehumidifier heats the house.

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#3373121 14-May-2025 17:31

freitasm:

@openmedia how can heatpumps help with humid interiors? Just using Heat won't dry. We tried with the DRY option but that's basically blasting cold air.

There are two types of humidity. Absolute humidity and relative humidity. Absolute humidity is the amount of water in the air, measured in g/m3. That doesn’t change with temperature.

Relative humidity measures the amount of water in the air before it will condense, measured as a percentage. The warmer air is the more water vapour it can carry and the lower humidity will be. As humans we feel relative humidity rather than absolute humidity as it relates to our ability to sweat. It’s why hot deserts are often described as having “dry heat.”

Raising the indoor temperature with heat pumps lowers the relative humidity and makes mold etc far less likely for the same absolute humidity.

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#3373385 14-May-2025 22:26

The ideal is heat-recovery ventilation or energy-recovery ventilation. You bring in fresh outside air, eject stale inside air, and run each of them through a heat exchanger so that the already cooled/heated outgoing air cools/warms the untempered incoming air.

ERV also transfers moisture from one set of air to the other. Many places with serious winters need to add humidity to the air in winter.

Despite the name, HRV (the company) does not sell real HRV systems. They're fairly expensive and hard to find in NZ, especially for residential.

richms

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#3373387 14-May-2025 22:44

freitasm:

@openmedia how can heatpumps help with humid interiors? Just using Heat won't dry. We tried with the DRY option but that's basically blasting cold air.

They only help when you are exchanging air with outside, as it will have a lower water content than whats inside when cold, and then it comes in and is warmed and it has a lower relative humidity.

It really only works when its below freezing outside so there is stuff all moisture in the air so not much needs to be swapped over to drop the humidity signifigantly. In 4-8 degrees outside when its at 100% misty full of water, that does nothing to drop it inside when exchanged.

Just do the same as any other heating method does. When in dry they are cooling with the fan speed optimised to pull out the most water rather than doing the most air cooling. Shouldnt be blasting, it should be a gently flow of really cold air that has had all the moisture taken out of it.

Richard rich.ms

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