How to top up single room MVHR?

[Soy Capitan]

Hello everyone. Having successfully installed two single room MVHRs in my bathrooms earlier this year, I'm now learning that building regs don't recommend having background ventilation (e.g. trickle vents) I'm the same house. I also see that whole home ducted MVHRs typically draw air from bathrooms and kitchens and put fresh air into bedrooms and lounges. If I can't use trickle vents in the other rooms, and I don't need more ventilation in my bathrooms, how else can I get my overall ventilation up to scratch without ripping out my new single room fans? Am I missing something obvious here?

 

[stem]

The idea with MVHR is that the building is as airtight as possible, so that all of the outgoing air, and all of the incoming air is forced through the heat exchanger. If air is entering or leaving via other ways, efficiency of the heat recovery process is reduced.

For a whole house system as you describe it, air is extracted from the kitchen and bathroom/s and passes through the heat exchanger. Fresh air from outside comes in through the heat exchanger where it picks up the heat and then delivers the air to the living rooms and bedrooms. The air then moves inside the house from the living and bedrooms towards the extraction points in the kitchen and bathroom/s, any other opportunities for air to leave or enter along the way are not wanted.

With single room MVHR it doesn't provide the transfer of air between rooms, so you can view the room in which they are located as a whole, so don't have any additional opportunities for air to enter or leave that don't go through the heat exchanger in that room. With the same sized inlet and outlet fans the air coming in and out of the single room should balance reasonably well without too many losses. Keeping the door from the bathroom to the rest of the house closed would help.

 

[Soy Capitan]

Thank you for that. I'm glad I asked this question now as I was planning on cutting 10mm gaps under my doors to encourage circulation. In my mind I was thinking while the single room MVHRs aren't supposed to ventilate more than said single room, its bound to help as air would naturally circulate between rooms. But from what you're saying it might actually be counter productive to allow airflow between the rooms with single MVHRs and rooms which are benefiting from the "rest of house" solution. I guess the last thing I need to figure out is which rooms I suck air from on top of the kitchen. Perhaps the front hallway would be beneficial as that might be wetter than other rooms with umbrellas and coats etc.