Problem with HRV

fitzie79

I have a HRV system installed in my house since it was built 3 years ago. Over the past year I have noticed that in the en-suite there are mold spores appearing on all the walls (external dry-lined wall and internal walls). On cold nights there is also severe condensation on the frame of the window of the en-suite. Additionally the adjoining bedroom also has condensation on the window on these nights. The shower in the en-suite is a power shower and there is a substantial amount of steam generated after a shower that the HRV does not seem capable of extracting (certainly not quickly) even though we religiously turn on the HRV system to it's max setting for 30 minutes once we go into the shower. I have a humidity monitor and the humidity in the en-suite is consistently 10 to 15% higher than anywhere else in the house.

I'm not sure if the system isn't balanced or isn't capable of extracting the steam quickly. I tried doing the plastic bag test on the extract/inlet pipes but the results were inconsistent and I can't tell for sure if there is a problem.

Does anyone have recommendations on someone in the Cork area who could check the system to see if there is an issue?

Are there air-tight extraction fans that I could install in the en-suite to help with extracting the steam (although obviously I'd rather recover the heat through the HRV)

sinnerboy

The HRV industry is attempting to organise itself in Ireland to agree , amongst other things , what a "Standard" commisoning test should comprise.

This is a relatively recent and still evolving development. Make contact here first.

ShiresV2

fitzie79 wrote: »

Are there air-tight extraction fans that I could install in the en-suite to help with extracting the steam (although obviously I'd rather recover the heat through the HRV)

Apologies if I am being obtuse but this is exactly what your HRV is. If it has been sized, installed and commissioned correctly then you shouldn't have any of the problems that you describe.

fitzie79

certainly my first preference is to resolve the issue with the HRV (if there is one) so that i recover the heat. However, if there is a problem that can't be (relatively cheaply) resolved then i want to investigate other potential solutions as having mould growing on the internal walls isn't something i want to leave continue. Therefore I asked about other alternatives like an air-tight extraction fan that could just take steam directly out of the house during a shower.

PS I appreciate your comments

MicktheMan

fitzie79 wrote: »

I have a humidity monitor and the humidity in the en-suite is consistently 10 to 15% higher than anywhere else in the house.

To have mould developing on internal walls means that your relative humidity levels are extremely high or there is another source of moisture in this area (leak),

What are the actual RH% readings in the ensuite and say the living room?

Also, who commisioned the mvhr system and would it not be possible to get the installer/commissioner to return to re-balance and re-check the flow rates through the various vents.

Finally, what is the heating like in the ensuite and what side of the house is the ensuite(n,s,e,w)?

fitzie79

i did a quick check of a few rooms earlier

en-suite 17.4degC/78% RH (after a shower this rises to high 90's even with max setting running on hrv)
bedroom 17.8degC/58% RH
living area 19.4degC/54% RH

i have considered getting the initial company back but if the issue was with the commisioning then i'd prefer to get someone back who may know a bit more about HRV and would be impartial

the heating in the en-suite is via a towel rad. the en-suite is on the north facing wall but the mold isn't confined to just this wall.

MicktheMan

The ensuite numbers are indeed very high values. I would expect these in a poorly ventilated bathroom. Any spaces with consistant RH values over 70% will have damp/mould problems. There is definetly something wrong with the setup and if it was me I would be getting the original installer back to sort it out.
So, questions I would be asking the mvhr company are:
1. is the ducting optimally designed and installed
2. was the correct type and size of ducting used
3. what were the flow figures per vent when the system was commissioned compared to now?

Where are the duct runs and is it possible that something happened to the ensuite leg since the system was installed (something restricting / blocking the ensuite ducting leg)?