Venting condensation from bathrooms using MVHR

igilvarry

Coming to the end of new house build but an issue has arisen with the rate of extracting condensation/steam from all 3 bathrooms - 1 downstairs, and 2 upstairs.

The issue is that when the showers are run in each bathroom for a period of no more than 10 minutes each time (representing an average shower length), and with the water temperature set to be that which would be normal for taking a shower (i.e. not too hot), the condensation can take up to 1.5 hours to be extracted through the MVHR vent depending on the bathroom in question. There is no other means to vent the condensation besides opening the doors of the bathrooms to allow it to pass through the other parts of the house.

Besides the impracticality of two people sharing the use of an ensuite as the second user would have to wait 1.5 hours to have a steam-free room to walk into, there is a concern also on the potential for mould/damp to thrive in such an environment.

I'm of the view that this situation implies the house is not practically liveable.

The house is concrete built, designed by an architect to be airtight. It has a MVHR system running continuously, UFH, and a geothermal heating system. In each bathroom there are roof lights which are not possible to open i.e. there are no windows that can open to the outside.

The house also incorporates an integrated garage which is accessed internally through one door which is connected to the utility room. Even though designed to be airtight, the architect has admitted that the door between garage and utility should have been sealed. Also, the base of the external garage doors are not sealed either. Is it possible that this issue is impacting the ability of the MVHR to efficiently function?

I should add that once the showers are run the MVHR seems to detect the extra humidity in the air as it auto-adjusts to a max setting which remains for a period of time, well over 1.5 hours, until it decides to then auto-adjust back to low-speed setting.

No6

If the MHRV can be shown to extract at the rate required by the regulations then its technically fine, it may possibly be undersized for the load required, who sized it? I would doubt very much it was the architect as for the seals on the door it shouldnt be a huge issue, it will have a small effect on your airtightness result but so will lots of otherthings, can an airseal be retrofitted to the door as a snag list item? Did you get the house pressure tested, what were the results and did you have any specified airtightness in your contract doccumentation or aggreement with your Architect.

Are the rooflights fixed or just high up? you can get poles to open most types!!

creedp

igilvarry wrote: »

Coming to the end of new house build but an issue has arisen with the rate of extracting condensation/steam from all 3 bathrooms - 1 downstairs, and 2 upstairs.

The issue is that when the showers are run in each bathroom for a period of no more than 10 minutes each time (representing an average shower length), and with the water temperature set to be that which would be normal for taking a shower (i.e. not too hot), the condensation can take up to 1.5 hours to be extracted through the MVHR vent depending on the bathroom in question. There is no other means to vent the condensation besides opening the doors of the bathrooms to allow it to pass through the other parts of the house.

Besides the impracticality of two people sharing the use of an ensuite as the second user would have to wait 1.5 hours to have a steam-free room to walk into, there is a concern also on the potential for mould/damp to thrive in such an environment.

I'm of the view that this situation implies the house is not practically liveable.

The house is concrete built, designed by an architect to be airtight. It has a MVHR system running continuously, UFH, and a geothermal heating system. In each bathroom there are roof lights which are not possible to open i.e. there are no windows that can open to the outside.

The house also incorporates an integrated garage which is accessed internally through one door which is connected to the utility room. Even though designed to be airtight, the architect has admitted that the door between garage and utility should have been sealed. Also, the base of the external garage doors are not sealed either. Is it possible that this issue is impacting the ability of the MVHR to efficiently function?

I should add that once the showers are run the MVHR seems to detect the extra humidity in the air as it auto-adjusts to a max setting which remains for a period of time, well over 1.5 hours, until it decides to then auto-adjust back to low-speed setting.

If your MHRV unit has a humidity monitor is should automatically speed speed up extraction to remove high levels of humidity quickly, as arise after a shower/bath/steam from cooking and then reduce back to normal once humidity levels return to a pre-set level. This should allow the MHRV unit to remove high levels of humidity quickly after a shower/bath thereby overcoming issues with moist air migrating around house. Check with installer as to what the set-up is for boosting extraction in response to high humidity levels. If this isn't working then you should ask the installer to check that the system is properly sized and functioning as required. Also check the filters to ensure they are not clogged as this might reduce the efficiency of the system.

BryanF

igilvarry wrote: »

Coming to the end of new house build ...

so how long are you in? your house will take several months to dry?

The issue is that when the showers are run ... there is a concern also on the potential for mould/damp to thrive in such an environment.

presuming your home is built to current regs with attention to detail, thermal bridges and proper ventialtion there should not be an issue with condensation once the house settles down.

I'm of the view that this situation implies the house is not practically liveable.

as no6 says get the commissioning MVHR supplier in, to check the system, condensatino should be dissipated in no more than a few minutes under normal conditions

The house is concrete built,

concrete does takes time to dry out..

designed by an architect to be airtight.

air-tightness test?

... there are no windows that can open to the outside.

have you quizzed your architect about this? in my opinion if a bathroom can be placed on an external wall, it should be, and should have a window/skylight provide for summer opening when MVHR is not necessary

the architect has admitted that the door between garage and utility should have been sealed... Is it possible that this issue is impacting the ability of the MVHR to efficiently function?

maybe, but surely there a remedial solution for this.again what the air-tightness test result?

I should add that once the showers are run the MVHR seems to detect the extra humidity in the air as it auto-adjusts to a max setting which remains for a period of time, well over 1.5 hours, until it decides to then auto-adjust back to low-speed setting.

there's something wrong with the commissioning of your MVHR system or your house is too leaky..

Do-more

It's not clear from your post whether you are living in the house yet or if this is just a test you have done running the showers.

If it's a test, are the bathrooms heated to their normal levels? If not then you will be producing much more condensation than if they were heated fully.

Has your HRV been fully commisioned and airflows balanced?

What sort of ducting has been used, rigid or flexible? Was it correctly designed and installed? How experienced is the duct designer? Were pressure drop calculations done?

fclauson

The black art of MVRH is really very simple - read part F - this will allow you to calculate the extract reates required for each room and for the whole building.

The you need to get a machine which will be at about 60% to deliver this (remember the back pressure so say a 450 machine is normally with no resistance but might fall to 300 when all the ducting is connected)

So if you required 350 - a 450 machine might not be large enough - you might need a 500

Do not operate a machine at 99% all the time - it will burn electricity and be inefficient

Hope that helps - I am suspecting you dampness is due to a machine being incorrectly sized

igilvarry

No6 wrote: »

If the MHRV can be shown to extract at the rate required by the regulations then its technically fine, it may possibly be undersized for the load required, who sized it? I would doubt very much it was the architect as for the seals on the door it shouldnt be a huge issue, it will have a small effect on your airtightness result but so will lots of otherthings, can an airseal be retrofitted to the door as a snag list item? Did you get the house pressure tested, what were the results and did you have any specified airtightness in your contract doccumentation or aggreement with your Architect.

What are the regulations that apply here?

The sizing was done by the company who supplied the whole solution - MVHR + Geothermal + UFH. They've got a top-notch reputation so I would be surprised if it was sized incorrectly.

The house was pressure tested but I have not been furnished with the results.

On the point re airtightness what should I be looking out for in the contract specification? Bit late I know to be asking now, but it never came up until this issue arose.

No6 wrote: »

Are the rooflights fixed or just high up? you can get poles to open most types!!

Rooflights are not possible to open - they're fixed panes.

igilvarry

creedp wrote: »

If your MHRV unit has a humidity monitor is should automatically speed speed up extraction to remove high levels of humidity quickly, as arise after a shower/bath/steam from cooking and then reduce back to normal once humidity levels return to a pre-set level. This should allow the MHRV unit to remove high levels of humidity quickly after a shower/bath thereby overcoming issues with moist air migrating around house. Check with installer as to what the set-up is for boosting extraction in response to high humidity levels. If this isn't working then you should ask the installer to check that the system is properly sized and functioning as required. Also check the filters to ensure they are not clogged as this might reduce the efficiency of the system.

When the showers have been run, the MVHR auto-adjusts to a high-speed setting but the effect is as described previously - taking over 1.5 hours for condensation to eventually disappear from bathroom. The filters in the MVHR were replaced also about 3 months ago.

When you say checking that the machine is properly sized - do you mean that I should check with the installer on the power/performance of the MVHR unit. As far as I know it's a Vortice unit but there may be different unit types in their range - I haven't checked.

fclauson

igilvarry wrote: »

What are the regulations that apply here?

Part F

The sizing was done by the company who supplied the whole solution - MVHR + Geothermal + UFH. They've got a top-notch reputation so I would be surprised if it was sized incorrectly.

The house was pressure tested but I have not been furnished with the results.

On the point re airtightness what should I be looking out for in the contract specification? Bit late I know to be asking now, but it never came up until this issue arose.

below 5 air changes per hour would be good

igilvarry

BryanF wrote: »

so how long are you in? your house will take several months to dry?

I am not in house yet. It's being snagged. I've also stated to architect that I don't think the house is liveable until this issue is resolved.

BryanF wrote: »

presuming your home is built to current regs with attention to detail, thermal bridges and proper ventialtion there should not be an issue with condensation once the house settles down. as no6 says get the commissioning MVHR supplier in, to check the system, condensatino should be dissipated in no more than a few minutes under normal conditions concrete does takes time to dry out..

BryanF wrote: »

air-tightness test?

I don't know the result of airtightness test - will have to check.

BryanF wrote: »

have you quizzed your architect about this? in my opinion if a bathroom can be placed on an external wall, it should be, and should have a window/skylight provide for summer opening when MVHR is not necessary
maybe, but surely there a remedial solution for this.again what the air-tightness test result? there's something wrong with the commissioning of your MVHR system or your house is too leaky..

Too late to change layout of house now but you have a point possibly here in that the ensuite (which takes longest to remove the condensation) is built within the house and no wall is an external wall.

creedp

igilvarry wrote: »

When the showers have been run, the MVHR auto-adjusts to a high-speed setting but the effect is as described previously - taking over 1.5 hours for condensation to eventually disappear from bathroom. The filters in the MVHR were replaced also about 3 months ago.

When you say checking that the machine is properly sized - do you mean that I should check with the installer on the power/performance of the MVHR unit. As far as I know it's a Vortice unit but there may be different unit types in their range - I haven't checked.

Yes. The installer/commissioner needs to confirm that the Unit is sufficiently sized for the house size allowing for losses in efficiency due to ducting. As you have an architect (unlike poor sod me) ask him to follow this up with MHRV guys and confirm that the unit meets Part F requirements.

igilvarry

Do-more wrote: »

It's not clear from your post whether you are living in the house yet or if this is just a test you have done running the showers.

If it's a test, are the bathrooms heated to their normal levels? If not then you will be producing much more condensation than if they were heated fully.

I am not living in the house yet, but the heat pump has been operational now for about 6 months. The floors are polished concrete and it was required to turn on the heat pump and slowly bring up the temperature.

Do-more wrote: »

Has your HRV been fully commisioned and airflows balanced?

Yes.

Do-more wrote: »

What sort of ducting has been used, rigid or flexible? Was it correctly designed and installed? How experienced is the duct designer? Were pressure drop calculations done?

The ducting was delivered as part of the total package: MVHR, geothermal, ufh. It's done by a company who by all accounts have a good reputation. The ducting is PVC as far as I can tell.

igilvarry

fclauson wrote: »

The black art of MVRH is really very simple - read part F - this will allow you to calculate the extract reates required for each room and for the whole building.

Where can I download part F?

fclauson wrote: »

The you need to get a machine which will be at about 60% to deliver this (remember the back pressure so say a 450 machine is normally with no resistance but might fall to 300 when all the ducting is connected)

So if you required 350 - a 450 machine might not be large enough - you might need a 500

Do not operate a machine at 99% all the time - it will burn electricity and be inefficient

Hope that helps - I am suspecting you dampness is due to a machine being incorrectly sized

The unit is a Vortice HR 400. The spec is at http://www.ventilnorte.com/vortice/docs/PROMETEO_HR_400.pdf

Can you tell from this what sizing is? All this technical stuff is beyond me hence the dumb questions.

sas

Where are the extracts located in the bathrooms relative to the door?

I'm told that they ideally should be located as far afrom the door as possible.

BryanF

Where can I download part F?

http://www.environ.ie/en/TGD/

part f

archtech

A couple of factors that effect MVHR Units include,

1. distance from the bathrooms to the unit itself, the longer the distance the less efficient the unit will be.
2. Size and type of ducting (flexible is less efficent)
3. Number of bends in the ductwork
4. Standard of installation of the ductwork

While you might have a very efficient unit to start with, poor design in terms of location of the unit could significantly reduce the efficiency of the unit and be the source of your problem.

Do-more

What size is your house?

Hard to give a definitive figure as there are a number of variables to consider, but that unit looks to be suitable up to a max. of approx. 200m2 (although I stand to be corrected on that!)

igilvarry

Do-more wrote: »

What size is your house?

Hard to give a definitive figure as there are a number of variables to consider, but that unit looks to be suitable up to a max. of approx. 200m2 (although I stand to be corrected on that!)

The overall house is 281m2. 30m2 of that is an integrated garage & boiler room attached to the house.

fclauson

So - on this forum we are not allowed to give specific guidence

but here is some general pointers - get proper guidence to get the right answer

if you read part F - do your calcs - work out the total extract volume you need - note when you have to apply the rule about 0.3 x sqM rule

convert to m3 for simplicyt (3.6 * l/s)

look at the chart in the pdf you pointed us towards for the unit

assume you back pressure will be around 200 (this is a very rough guide and should be caculated with knowedge of your system - there are many variables - poorly designed systems could be higher)

then look at ther perf graph - I think you might find the unit is expected to be running at 80 or 90% of capacity most of the time just to cover your basic requirement - this is not a good spot to be on the graph

hope this helps

sinnerboy

OP check your filters. Fitted 3 months ago on what remains a site , I would expect them to be be clogged.

Check for any other obstruction(s) in the system too i.e. if accessible at your in line silencers.

Hopefully your issue will be bog simple to fix.