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Hi, As background we have recently completed a deep retrofit of my 1960’s family home housing three adults and three children. We added an extension, new roof and are aiming for an EnerPHit standard of thermal performance and airtightness. Measures included new triple glazing for half the windows, IWI and CWI insulation, lime parged walls, air tightness taping throughout the house, new air source heat pump and an MVHR system. A recent air tightness test has shown we have gone from a leaky 15 ACH to 5. The test was done with 14 year old double glazed PVC windows and an air conditioning unit left untaped, knowing they are a little leaky. So far so good. Three months ago, after a long wait, we switched on the MVHR system: A Zehnder Comfoair Q350 and steel ducts from 21 Degrees who also designed and commissioned the system. The commissioning process didn’t go to plan as a young engineer connected up the waste pipe to the wrong side of the machine, causing a leak a few days later. Fortunately, this was found quickly, and the waste pipe was switched over. Unfortunately, the system, hasn’t performed as well as I had hoped. I did ask 21 Degrees if it had been damaged and to their credit, they sent another engineer over who found it hadn’t. Here are the issues: The kitchen and utility rooms seem to be clear of condensation but the two bathrooms, after hot showers, remain damp after two hours and longer, so we have reverted to opening bathroom windows until the condensation has cleared. We chose not to have extraction fans fitted in these rooms, believing the MVHR extraction vents would suffice. Sadly, increasing the ventilation rate from the normal ‘2’ setting to the high ‘3’ setting makes no difference. I noticed the downstairs bathroom outlet has less suction power – perhaps a third lower than the others - unable to hold a paper tissue on the normal or high settings. I should say here, adjusting the outlet vents doesn’t make a difference. Questions 0. Are my bathroom extraction vents not working properly? 1. Should an MVHR system be able to clear bathrooms of condensation? 2. Speaking to 21 Degrees I was surprised to hear that they don’t expect the system to clear the bathroom condensation. Am I right to feel disappointed here? 3. Is it a balancing issue, whereby the supply and extraction vents need adjusting by someone, unlike me, who knows what they are doing and has the right tools? 4. You can feel the soft gentle supply of air from the supply vents but, unlike some MVHR users on this website, the circulating air flow sees lame, i.e. it doesn’t whistle under closed doors. My air supply flow can only be felt close up at the outlet ducts. Is something wrong here? I am about to lay my carpets and cut my doors to keep the recommended 10mm air gap beneath. If there any issues with the MVHR system I would obviously like to address them before this. I appreciate any thoughts and help with this. Thank you Ian