House Ventilation & Air vent drafts

Luc84

Hello
I recently bought a new build (A2). The house has a mechanical ventilation system with air vents in all toilets and the kitchen, so air is constantly pulled from the more humid rooms.

In addition I have air vents (holes in the wall) in every room where drafts can be easily felt leaving the house generally cold. In some cases condensation can be seen in the grates, especially during these cold nights, I presume due to the cold air coming in and condensing in the warmer internal grate.

I am currently thinking to install some black hole air vents as MVHR are a little too expensive for the moment.

I would like to ask if anybody has had a similar experience and how was it solved. The house, as I usually keep the heating on few hours split between the Morning and Evening, generally is at at temp of 17/18 c and would like to bring it to an average of 20 at least and just control the drafts.

Any tip and feedback would be much appreciated

Thanks

listermint

Yes the anti draught vents you mention are a good cost effective method for this.

Also the control of your heating system and its run times is vital for maintaining levels of comfort.

At A2 and constant 17-18 degrees it sounds like something isn't right. The vents id be unsure if they are the source.

What's th heating controls look like on terms of daily operation.

The rads TRVs ?

Luc84

listermint wrote: »

Yes the anti draught vents you mention are a good cost effective method for this.

Also the control of your heating system and its run times is vital for maintaining levels of comfort.

At A2 and constant 17-18 degrees it sounds like something isn't right. The vents id be unsure if they are the source.

What's th heating controls look like on terms of daily operation.

The rads TRVs ?

Thanks for your answer. In reation to your question I can turn on the hot water, 1st and 2nd floor indipendently. During the day I turn it on only for the 1st floor, in the evening approx 1 or 2 hours for the 2nd floor too. I have set the radiators to around 3 +or- depending on the room. And finally set the water to 50c temperature.

Luc84

Luc84 wrote: »

Thanks for your answer. In reation to your question I can turn on the hot water, 1st and 2nd floor indipendently. During the day I turn it on only for the 1st floor, in the evening approx 1 or 2 hours for the 2nd floor too. I have set the radiators to around 3 +or- depending on the room. And finally set the water to 50c temperature.

I won't comment on the house temps but your water is a breeding ground for legionnaires disease at 50. It needs to be above 60

Luc84

SouthWesterly wrote: »

I won't comment on the house temps but your water is a breeding ground for legionnaires disease at 50. It needs to be above 60

Thanks for this, it seemed low to me too. But i was told that the boiler it's most efficient at this temperature.

listermint

Luc84 wrote: »

Thanks for your answer. In reation to your question I can turn on the hot water, 1st and 2nd floor indipendently. During the day I turn it on only for the 1st floor, in the evening approx 1 or 2 hours for the 2nd floor too. I have set the radiators to around 3 +or- depending on the room. And finally set the water to 50c temperature.

Is it thermostat controlled, or just on for 1st floor

Luc84

listermint wrote: »

Is it thermostat controlled, or just on for 1st floor

I have thermostats in both floors and could set it up to auto so that it would be controlled by it. For the moment I am just turning it on for 2 hours in the morning and 2 hours in the evening. I know it's not the best approach but I am waiting for my first bill and tune the approach as i go:).

loyatemu

I'm not sure black hole vents will help if you have air constantly being sucked out by fans. AFAIK they're designed to stop draughts caused by external wind. If air is being removed from the house constantly via the kitchen and bathrooms, it has to get back in at the same rate to equalise the pressure.

listermint

loyatemu wrote: »

I'm not sure black hole vents will help if you have air constantly being sucked out by fans. AFAIK they're designed to stop draughts caused by external wind. If air is being removed from the house constantly via the kitchen and bathrooms, it has to get back in at the same rate to equalise the pressure.

But, the fans should only be activated in those areas when needed. i.e showering or cooking...?

loyatemu

listermint wrote: »

But, the fans should only be activated in those areas when needed. i.e showering or cooking...?

OK - so it's just regular extractor fans, with (effectively) holes in the wall in the other rooms. Bizarre that this is good enough for an A2 rating, but seems to be the case from various threads here on the topic.

awec

listermint wrote: »

But, the fans should only be activated in those areas when needed. i.e showering or cooking...?

If it's the same as what's in our house then they run constantly. They're not extractor fans that you can turn on and off.

They aren't actually fans, they are vents in the ceiling of the "wet" rooms (kitchen + bathrooms) that suck in moist air and these vents are ducted to a unit in the attic and vented outside.

listermint

awec wrote: »

If it's the same as what's in our house then they run constantly. They're not extractor fans that you can turn on and off.

They aren't actually fans, they are vents in the ceiling of the "wet" rooms (kitchen + bathrooms) that suck in moist air and these vents are ducted to a unit in the attic and vented outside.

They shouldnt be on constantly though, they should be linked to Humidity sensor.

listermint

loyatemu wrote: »

OK - so it's just regular extractor fans, with (effectively) holes in the wall in the other rooms. Bizarre that this is good enough for an A2 rating, but seems to be the case from various threads here on the topic.

The rating system BER is a handy guideline within a framework, But is in reality a big back of ****e in terms of measuring comfort in the real world.

sydthebeat

listermint wrote: »

They shouldnt be on constantly though, they should be linked to Humidity sensor.

if its a "Centralized Continuous Mechanical Extract Ventilation (CMEV)" system then they are set to be continuous, and based on either occupancy calculated bedroom sizes, or by floor area.

are you assuming DCV here?

Luc84

awec wrote: »

If it's the same as what's in our house then they run constantly. They're not extractor fans that you can turn on and off.

They aren't actually fans, they are vents in the ceiling of the "wet" rooms (kitchen + bathrooms) that suck in moist air and these vents are ducted to a unit in the attic and vented outside.

Yes that's it actually

listermint

sydthebeat wrote: »

if its a "Centralized Continuous Mechanical Extract Ventilation (CMEV)" system then they are set to be continuous, and based on either occupancy calculated bedroom sizes, or by floor area.

are you assuming DCV here?

I would be extremely surprised on a cmev in an Irish house . They build them to bare bones budget i would assum dcv ya

awec

https://www.solerpalau.com/en-en/whole-house-extract-units-ozeo-e-ecowatt-1127-serie/

That's what we have.

Apparently it can come with an optional RF controller to set the suction power but we don't have that installed, or if we do, I don't know where the controller is!

Is that CMEV?

Calahonda52

Whole house extract units that ensure permanent renewal of air in single dwelling houses or multi-dwelling blocks (individually). The unit is complemented with self-adjusting extraction BAR valves, (installed in kitchen, toilets, bathrooms) and self-regulated air inlets located in the main rooms (dining rooms, bedrooms).
This range has available a CO2 model that adjusts the airflow according to the CO2 concentration detected by the sensor.

so if you dont have the air inlets as described then its pure extract without any controls.

awec

And this is totally different to MHRV? Or is it part of MHRV?

listermint

awec wrote: »

And this is totally different to MHRV? Or is it part of MHRV?

MHRV is a centralised system within the dwelling which connects all rooms via ducts and balances the air temp across the system, taking hotter air from warmer or humid rooms recovering that heat to distribute elsewhere. The central unit itself is then connected directly outside to exhaust spent stale air and draw in fresh air for the system.

Its more expensive

Calahonda52

While its more expensive, ,it does have heat recovery which makes them maybe 90 % efficient, and offer wonderful air quality through good filtration

awec

listermint wrote: »

MHRV is a centralised system within the dwelling which connects all rooms via ducts and balances the air temp across the system, taking hotter air from warmer or humid rooms recovering that heat to distribute elsewhere. The central unit itself is then connected directly outside to exhaust spent stale air and draw in fresh air for the system.

Its more expensive

I see.

And retrofitting MHRV into an existing house (that's A rated built in the past 3/4 years) is something that's feasible or not feasible?

No intention of doing it, but just curious.

MicktheMan

Luc84 wrote: »

Hello
I recently bought a new build (A2). The house has a mechanical ventilation system with air vents in all toilets and the kitchen, so air is constantly pulled from the more humid rooms.

In addition I have air vents (holes in the wall) in every room where drafts can be easily felt leaving the house generally cold. In some cases condensation can be seen in the grates, especially during these cold nights, I presume due to the cold air coming in and condensing in the warmer internal grate.

I am currently thinking to install some black hole air vents as MVHR are a little too expensive for the moment.

I would like to ask if anybody has had a similar experience and how was it solved. The house, as I usually keep the heating on few hours split between the Morning and Evening, generally is at at temp of 17/18 c and would like to bring it to an average of 20 at least and just control the drafts.

Any tip and feedback would be much appreciated

Thanks

The bolded bit intrigues me. Can you elaborate? Any pics (both close up and from a distance) of these "grates" with condensation?

MicktheMan

awec wrote: »

I see.

And retrofitting MHRV into an existing house (that's A rated built in the past 3/4 years) is something that's feasible or not feasible?

No intention of doing it, but just curious.

Generally not unless layout allows (for example a bungalow with access to all ceilings via attic) but care needed as generally the system will be outside the thermal envelope which generally negatively impacts efficiency of heat exchanger.

Alkers

Can you post s pic of the vents (inlets) you have?

It seems like you have s dcv system but with standard wall vents?

Luc84

Alkers wrote: »

Can you post s pic of the vents (inlets) you have?

It seems like you have s dcv system but with standard wall vents?

Thanks all for the replies, it's really appreciated.

I will get few pics today, but basically the wall vents are just a whole in the wall with round grates on the outside and rectangualr inside connected by a pipe. Today they are dry for example, but on the inside in some instances I have noticed very small droplets of water forming on the grate. Not big enough to leak down to the wall (although that happens on the outide, it's possible to see the sing of the water going down) but just enough to be spotted by naked eye.

In relation to the kitchen and toilets, the air pump sits in the attic and as far as i can see it's always on and the air goes out.

listermint

Luc84 wrote: »

Thanks all for the replies, it's really appreciated.

I will get few pics today, but basically the wall vents are just a whole in the wall with round grates on the outside and rectangualr inside connected by a pipe. Today they are dry for example, but on the inside in some instances I have noticed very small droplets of water forming on the grate. Not big enough to leak down to the wall (although that happens on the outide, it's possible to see the sing of the water going down) but just enough to be spotted by naked eye.

In relation to the kitchen and toilets, the air pump sits in the attic and as far as i can see it's always on and the air goes out.

Theyre a terrible system from the description of it. BER my arse its a painful inadequate system of checkbox calculations

cruizer101

I'm no expert but condensation on the vents to me would indicate that air is going out them rather than in.

As warm air from the house goes out the vent it cools and can't hold as much moisture so some of it condenses.
Cold air coming into the house would be warming up so its capacity for moisture would increase.

It still seems strange for it to condense though, presumably the vents are plastic. Condensation would normally form on glass or metal surfaces with high heat conductivity.

It sounds like the humidity in the house is high, but if air is constantly being extracted from the kitchen and bathrooms where most moisture is generated, humidity shouldn't be much of an issue.

FitzElla

listermint wrote: »

Theyre a terrible system from the description of it. BER my arse its a painful inadequate system of checkbox calculations

I've done a bit of looking into this:

A lot of new A2 rated builds seem to be meeting the ventilation requirements by installing a Centralized Continuous Mechanical Extract Ventilation system (CMEV) for wet rooms (bathrooms, kitchens, utility rooms) and fresh air being supplied by hole in the wall background ventilators. This is obviously a cheaper approach than doing it right and putting in a MHRV system, but is one of the suggested approaches in the building regulations so 100% allowed.

The big problem with the hole in the walls approach is they often over ventilate with ice cold air blowing in and also they let in a lot of background noise for those in urban areas. Personally I think the idea of a modern A2 house with a big hole in every room with a bit of pipe stuck in is a bit crazy.

As the new builds are so air tight blocking or obstructing the supply vents could really impact the air quality. They vents should have a minimum free area of 7000mm2 according to the building regs, so this in theory rules out a lot of the blackhole anti-draught ventilators (usually only 3000 to 4000 mm2 free area).

So the options are as I see it:

• retrofit MHRV at great expense and necessitating installing ducting with all the disruption that entails to existing house.
• Ductless MHRV? No idea how well these work, especially with a CMEV in place already. Also need power for each unit.
• Some other demand control ventilation retrofit? I haven't found any option here but imagine there must be something out there.

If anyone knows a product or company that could assist I would love to hear.

Alkers

FitzElla wrote: »

I've done a bit of looking into this:

A lot of new A2 rated builds seem to be meeting the ventilation requirements by installing a Centralized Continuous Mechanical Extract Ventilation system (CMEV) for wet rooms (bathrooms, kitchens, utility rooms) and fresh air being supplied by hole in the wall background ventilators. This is obviously a cheaper approach than doing it right and putting in a MHRV system, but is one of the suggested approaches in the building regulations so 100% allowed.

The big problem with the hole in the walls approach is they often over ventilate with ice cold air blowing in and also they let in a lot of background noise for those in urban areas. Personally I think the idea of a modern A2 house with a big hole in every room with a bit of pipe stuck in is a bit crazy.

As the new builds are so air tight blocking or obstructing the supply vents could really impact the air quality. They vents should have a minimum free area of 7000mm2 according to the building regs, so this in theory rules out a lot of the blackhole anti-draught ventilators (usually only 3000 to 4000 mm2 free area).

So the options are as I see it:

• retrofit MHRV at great expense and necessitating installing ducting with all the disruption that entails to existing house.
• Ductless MHRV? No idea how well these work, especially with a CMEV in place already. Also need power for each unit.
• Some other demand control ventilation retrofit? I haven't found any option here but imagine there must be something out there.

If anyone knows a product or company that could assist I would love to hear.

Does it not make sense that smaller vents could be used with the CMEV? The constantly running fan will ensure more air is drawn through the vents than a passive system?

For your last bullet - Humidity controlled vent inlets (to replace the OPs wall vents) seems like the most cost-efficient solution here. Is the CMEV one speed the entire time or does it change with humidity etc?

Alun

Alkers wrote: »

Does it not make sense that smaller vents could be used with the CMEV? The constantly running fan will ensure more air is drawn through the vents than a passive system?

When I lived in the Netherlands our house (built in 1986!) had such a system and the only source of fresh air input was small vents built into the windows as far as I remember. Absolutely no issues with condensation, damp etc.

listermint

Alun wrote: »

When I lived in the Netherlands our house (built in 1986!) had such a system and the only source of fresh air input was small vents built into the windows as far as I remember. Absolutely no issues with condensation, damp etc.

tbf, vastly different climates

Alun

listermint wrote: »

tbf, vastly different climates

Not particularly. Maybe not quite as damp as here, but not "vastly" different by any means.

FitzElla

Alkers wrote: »

Does it not make sense that smaller vents could be used with the CMEV? The constantly running fan will ensure more air is drawn through the vents than a passive system?

For your last bullet - Humidity controlled vent inlets (to replace the OPs wall vents) seems like the most cost-efficient solution here. Is the CMEV one speed the entire time or does it change with humidity etc?

The CMEV is one speed with an on/off boost function, presumably set at a level to meet the min requirements of 0.3 l/s extract per m2 internal floor area.

I agree with your thinking around the smaller vents, but the building regs specifically deal with this set up and specify 7000 mm for each habitable room. Presumably they have done the research to back that up.

listermint

FitzElla wrote: »

The CMEV is one speed with an on/off boost function, presumably set at a level to meet the min requirements of 0.3 l/s extract per m2 internal floor area.

I agree with your thinking around the smaller vents, but the building regs specifically deal with this set up and specify 7000 mm for each habitable room. Presumably they have done the research to back that up.

Ya, but you would also want the gaps underneath each door to be maintained to spec levels too. And those are easily hung wrong or flooring is put in or new doors are added.

FitzElla

listermint wrote: »

Ya, but you would also want the gaps underneath each door to be maintained to spec levels too. And those are easily hung wrong or flooring is put in or new doors are added.

Agreed. But there still doesn't seem to be a solution that complies with the building regs and doesn't involve a massive retrofit.

Alkers

FitzElla wrote: »

The CMEV is one speed with an on/off boost function, presumably set at a level to meet the min requirements of 0.3 l/s extract per m2 internal floor area.

I agree with your thinking around the smaller vents, but the building regs specifically deal with this set up and specify 7000 mm for each habitable room. Presumably they have done the research to back that up.

So why bother with the CMEV if you just need the larger vents in every room in any case?

Alkers

listermint wrote: »

Ya, but you would also want the gaps underneath each door to be maintained to spec levels too. And those are easily hung wrong or flooring is put in or new doors are added.

Aereco specify 2cm air gaps beneath all internal doors

loyatemu

Alkers wrote: »

Aereco specify 2cm air gaps beneath all internal doors

interestingly my 1970s concrete house has air vents above each bedroom door (it also has all the airtightness of a string vest :pac:)

awec

Alkers wrote: »

Does it not make sense that smaller vents could be used with the CMEV? The constantly running fan will ensure more air is drawn through the vents than a passive system?

For your last bullet - Humidity controlled vent inlets (to replace the OPs wall vents) seems like the most cost-efficient solution here. Is the CMEV one speed the entire time or does it change with humidity etc?

We have the system he described but with trickle vents in windows instead of wall vents, so it’s definitely possible.

poker--addict

How do you know if a house is sufficiently ventilated and getting fresh air? Considering a house which is B2 from about 2006. There is a vent at top of windows which can be slid open. There is no heat recovery or mechanical systems generating flow.

No signs of moisture, so it’s more an air quality concern behind the question.

Lumen

The condensation is probably just a consequence of warm, humid, internal air condensing on the vent cover which has been cooled by the air coming in. I wouldn't worry about it particularly.

Lumen

The key issue is whether the house is being over ventilated in certain conditions, e.g. high wind, or whether the drafts are happening whenever the extract system is running.

You can replace the passive vents with unpowered active vents which are humidity sensitive, e.g. from Aereco. I don't know what the impact would be on the central extract though, if it's running continuously.

There are various vent baffle arrangements possible.

Biker1

Under Part F 2019 the minimum equivalent opening for the room vents when using a mechanical extract ventilation system is 2500mm2 and a 10mm gap under all doors is also required.

C. Eastwood

https://www.boards.ie/discussion/comment/118385006#Comment_118385006

poker-addict. Your house was built 2006. The Technical Guidance Document F Ventilation was the applicable Building Regulations 2002 document which should have been complied with. It stated as follows:-

“background ventilation” means ventilation by means of a secure ventilation opening (or openings) consisting of a wall or window ventilator with a controllable ventilation grill and located so as to reduce drafts;

“habitable room” means a room in a dwelling used for living or sleeping purposes but does not include a kitchen having a floor area of less than 6.5 m2;

DWELLINGS

Habitable Rooms

1.5 In a habitable room other than a utility room, a kitchen or a room containing a kitchen, the following provision for ventilation should be adequate:

(a) a ventilation opening suitable for background ventilation having a total area of not less than 6500 mm2.

This could be achieved by a 100 mm dia pipe / hole through the wall = approx 7,500 mm2

It could also be achieved by a trickle vent in the Window frame of size 6,500 mm2.

It is very important that if there is the 100 mm hole through the wall, it must be lined - usually with a PVC duct (pipe) and it is very important that this is sealed at both ends to prevent damp air from the cavity getting in to the Vent duct.

poker--addict

Ok, I guess the vent in windows is sufficient, as long as I keep some of them actually open to allow airflow. They were all closed when i checked them out today. Opened a few now in a way I think should generate some flow and see stale air exhausted. That should be fine?