Brivis gas central heating - adding fresh air ventilation

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snowfly

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#315158 18-Jun-2024 11:33

We have a 1960's house that we have renovated over the years, added additional rooms, double glazing, new insulation in walls/roof/underfloor (ground moisture barrier covers approx 40% under house, still yet to do the rest).

For heating we have a Brivis ducted gas central heating system (was already in the house), with 12 vents (to all bedrooms, bathrooms, kitchen, living, lounge, etc), all ducted under the house (house is on piles).

The Brivis system works well, and since renovations the moisture in the house has dropped, house is warmer in winter, but still get some moisture on the windows during winter.
I have a Tapo T310 sensor in the house, currently reporting between 65-75% relative humidity, with temps between 18-22 degrees.

We use the original 'dumb' Brivis NC3 controller to set schedules for the heating to turn on/off - but thinking of adding the Brivis Touch Wi-fi controller, and integrating into Home Assistance for some smart capabilities.

So looking at options for adding ventilation, so far thought of the following:

Dehumidifier - thought about it, but doesn't seem like a permanent solution
Full ventilation system (e.g. DVS / smartvent) - thought about it, but don't see the point in paying of a separate system of ventilation ducts in ceiling, when we already have ducts under the house from the brivis unit that we could re-use
Adding fresh/ventilated air into the Brivis system

After some research I see that the Bonaire gas system had a Fresh Air Ventilation Add-On kit, but can't find the equivalent for Brivis, so seems they don't have one.

Possible DIY solution:

Motorised Y damper installed in return air duct to Brivis furnace
New duct from this damper to outside the house - with inline filter(s)
Make the damper 'smart': (Brivis touch wifi controller + home assistant + smart plug on damper)
1. e.g. when Brivis system runs in fan-only mode, switch damper, so air is pulled from outside.
  When fan-only mode turned off, switch damper, so air is pulled from re-circulation vent inside house.

End result: being able to pull in fresh air from outside, rather then keep recirculating stale air inside the house, especially when the brivis is run in fan-only mode.

Has anyone else done anything similar, or have a Brivis (or similar) gas ducted system that they have added ventilation to?

@timmmay - I read that you did something similar, with a positive pressure outlet near your ducted heating input, and ran your ducted heating in fan mode. How is that working for you?
Post: https://www.geekzone.co.nz/forums.asp?forumid=141&topicid=295841&page_no=1#2907636

Thanks

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#3250365 18-Jun-2024 12:03

I've got the Bonaire system with fresh air add on and its not everything it is cracked up to be (previous moan here: https://www.geekzone.co.nz/forums.asp?forumid=141&topicid=204836&page_no=1#1656692). You don't really want fresh air being introduced while trying to heat. But with my system at least, toggling between fresh and recirculated/heating modes isn't straightforward or automatic. I've had some ideas about how to sort this out, but have never gotten around to either finding the time or money to deploy a solution. TBH, if I had my time again, I probably would have gone for a separate mechanical ventilation system and be done with it. But if you come up with something clever, very keen to hear about it!

tweake

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#3250366 18-Jun-2024 12:07

i would add a ventilation fan and have it pipe into the return, and have the heating system fan run constantly. if you had the heating fan off it will blow air back through the return so would need some dampers to stop that.

the type of ventilation will depend a bit on whats done to the house. 1960's house a PPV system is fine unless the floors, walls etc have been well sealed then a balanced system may be better.

something to look at is summer kit, ie external air intake. not hard to make a simple auto version.

also note with some house designs you have to ONLY use external air intake.

tweake

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#3250371 18-Jun-2024 12:14

mdf:

You don't really want fresh air being introduced while trying to heat.

you want fresh air ALL the time, regardless of the heating and cooling. if your having trouble heating because of the ventilation air, then the ventilation air is way to much or the heating is way to small. ventilation air volume is so small it should not impact any good heating system.

a lot of the systems on the market will lower the amount of fresh air when its colder, with the idea of it makes up for it when its warmer. it works okish.

timmmay

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#3250402 18-Jun-2024 13:26

Having the positive pressure outlet near the ducted system inlet seems to work okay. The bedroom air is fresher when we use it. It's probably not as good as a properly integrated system but it's a lot cheaper and easier.

mdf

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#3250403 18-Jun-2024 13:28

tweake:

you want fresh air ALL the time, regardless of the heating and cooling. if your having trouble heating because of the ventilation air, then the ventilation air is way to much or the heating is way to small. ventilation air volume is so small it should not impact any good heating system.

a lot of the systems on the market will lower the amount of fresh air when its colder, with the idea of it makes up for it when its warmer. it works okish.

Oh, 100% agreed. "Good" being the operative word here though. Systems may have come along since the version I've got, but I don't think that adjective decribes mine. The manual says not to run heating with fresh air on, with (from memory here) something like a 20-25% increase in heating costs. Based on what you've said, I'm guessing too much ventilation air is my issue.

tweake

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#3250414 18-Jun-2024 14:15

timmmay: Having the positive pressure outlet near the ducted system inlet seems to work okay. The bedroom air is fresher when we use it. It's probably not as good as a properly integrated system but it's a lot cheaper and easier.

thats another way. dump the ventilation air into the hallway next to the return. however when the heating system fan is off you get poorer ventilation as a lot of it will go to where its easiest to get out of the house and bypass a lot of the rooms. hence distributed ventilation is much better.

timmmay

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#3250415 18-Jun-2024 14:19

I have automation that turns on the positive pressure ventilation and fan mode for the ducted heat pump at the same time. The time it starts and the duration varies each day. It also comes on at a couple of times I know heating will be on.

I have found that I don't need constant ventilation. It's not like I'm running a horse stables or have a thousand people in the house.

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tweake

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#3250416 18-Jun-2024 14:21

mdf:

tweake:

you want fresh air ALL the time, regardless of the heating and cooling. if your having trouble heating because of the ventilation air, then the ventilation air is way to much or the heating is way to small. ventilation air volume is so small it should not impact any good heating system.

a lot of the systems on the market will lower the amount of fresh air when its colder, with the idea of it makes up for it when its warmer. it works okish.

Oh, 100% agreed. "Good" being the operative word here though. Systems may have come along since the version I've got, but I don't think that adjective decribes mine. The manual says not to run heating with fresh air on, with (from memory here) something like a 20-25% increase in heating costs. Based on what you've said, I'm guessing too much ventilation air is my issue.

bonaire mentions cooling (with a gas heating system??) and that "Refresh all the air within your home up to five times every hour as the add-on system circulates and filters the air.". now 5 ach is a HUGE amount for ventilation, thats potentially house damaging. (normal is 0.35 or 0.5 ach). thats certainly would "cool" the house or make heating difficult.

tweake

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#3250420 18-Jun-2024 14:38

timmmay: I have automation that turns on the positive pressure ventilation and fan mode for the ducted heat pump at the same time. The time it starts and the duration varies each day. It also comes on at a couple of times I know heating will be on.

I have found that I don't need constant ventilation. It's not like I'm running a horse stables or have a thousand people in the house.

i'm not a fan of the store then purge style. rather push it outside as soon as possible.

snowfly

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#3250518 18-Jun-2024 17:28

Thanks for the responses and discussion.

Sounds like introducing fresh outside air is a good common suggestion, just whether all the time, part time, or a small amount.

So basically a 'summer kit' DIY approach sounds like it could work, tech details:

Install a 24vac controlled motorised damper in the return duct (between return vent in house and brivis unit)
New duct and inline filter to outside intake grill
Shelly (or similar) to control the 24vac motorised damper
Brivis touch wi-fi kit (making the 'dumb' brivis heater smart)
Brivis touch Home Assistant integration
HA automation:
1. When brivis in mode HVAC_MODE_FAN_ONLY, call shelly to open 24vac damper (opening duct to pull in outside air)
2. When brivis in any other mode (e.g. OFF or HEAT), call shelly to close 24vac damper (closing duct to outside air)

Effectively automating the outside air intake, when we are using the heater, don't pull in outside air (or could override manually if we wanted)
And only pull in outside air in fan mode.

And run the 'fan only' mode in a schedule, e.g. during the morning to vent the house with outside air.

Not looking for constant ventilation (as @timmmay mentions), just something I can run on a desired schedule to bring outside air into the house.

Could even improve the automation to check temp/humidity sensors inside and outside house, and check the difference between the two, before switching on the fan & switching damper to outside air.

timmmay

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#3250521 18-Jun-2024 17:37

When I do my daily ventilation, I crack open the window in one bedroom so that I can control where the air leaves the house. It's usually on the side it's not raining.

jonherries

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#3250537 18-Jun-2024 18:44

We have an older Brivis (20 years ish) - they have/had an add on card that I have had a nest thermostat connected to, which then connects to homebridge. Works well.

We are close to having to replace it though because the parts aren't available. We are looking at ducted air conditioning to replace.

Our 100 year old house has been excavated under the floor to give 500mm clearance in general with plastic everywhere + insulation. I remain convinced removing/lowering the soil level was the best investment.

Our inside humidity is in mid 60s, upto mid 70s in kitchen when cooking. We are in Wellington on the peninsula, so generally high humidity outside.

Jon

tweake

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#3250539 18-Jun-2024 18:49

snowfly:

Thanks for the responses and discussion.

Sounds like introducing fresh outside air is a good common suggestion, just whether all the time, part time, or a small amount.

So basically a 'summer kit' DIY approach sounds like it could work, tech details:

Install a 24vac controlled motorised damper in the return duct (between return vent in house and brivis unit)
New duct and inline filter to outside intake grill
Shelly (or similar) to control the 24vac motorised damper
Brivis touch wi-fi kit (making the 'dumb' brivis heater smart)
Brivis touch Home Assistant integration
HA automation:

When brivis in mode HVAC_MODE_FAN_ONLY, call shelly to open 24vac damper (opening duct to pull in outside air)
When brivis in any other mode (e.g. OFF or HEAT), call shelly to close 24vac damper (closing duct to outside air)

Effectively automating the outside air intake, when we are using the heater, don't pull in outside air (or could override manually if we wanted)
And only pull in outside air in fan mode.

And run the 'fan only' mode in a schedule, e.g. during the morning to vent the house with outside air.

Not looking for constant ventilation (as @timmmay mentions), just something I can run on a desired schedule to bring outside air into the house.

Could even improve the automation to check temp/humidity sensors inside and outside house, and check the difference between the two, before switching on the fan & switching damper to outside air.

basically no.

you need a fan for the ventilation. just putting a duct to the return won't do anything. a simple cheap ventilation system kit would work ok. hook that up to the return or vent next to the return (which is easier to get to work when heating is off).

you can't just put a damper in that will block off the return and feed in outside air. that can cause damage to your house as it will pressurize the living hell out of the house.

scheduling ventilation is okish. better to use one of the controllers so it runs faster when temps are good.

use an ec fan, totally variable, low power usage. have a look at https://www.weiss.co.nz/product-home-ventilation but there is similar things around.

using other sensors, probably not worth the effort unless you have a high performance home. humidity is a waste of time because the air your bringing in is a major source of humidity. co2 is ok if you get the right sensors $$ and can connect it to increase ventilation (rather than on/off).

tweake

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#3250540 18-Jun-2024 18:54

timmmay: When I do my daily ventilation, I crack open the window in one bedroom so that I can control where the air leaves the house. It's usually on the side it's not raining.

thats defeats a lot of the ventilation.

the whole idea of ppv is that it leaks out of each room. if you make it leak out of one room, then only one room is getting ventilation as all the air will go to that room. with standard houses there is no need for to open a window. it has enough normal leakage, plus the bath fans and rangehoods to leak through.

tweake

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#3250541 18-Jun-2024 18:57

jonherries:
Our 100 year old house has been excavated under the floor to give 500mm clearance in general with plastic everywhere + insulation. I remain convinced removing/lowering the soil level was the best investment.

Jon

😍 hell yeah 🍺

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