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HRV making house very cold

  • 12-12-2022 9:23pm
    Registered Users Posts: 222 ✭✭

    Hi lads, my house was renovated this year have found the house freezing the past few weeks, despite having an insulation wrap on it. The air coming through the HRV vents is freezing and I'm just wondering if this is normal?


  • Registered Users Posts: 8,199 ✭✭✭ongarite

    Who is the manufacturer of your HRV? Does it have a heat exchanger to heat incoming outside air? Some models also have a supplemental heater or defrost in very cold weather like we have now?

    How cold is freezing? Air moving at high velocity always feels colder than it really is.

  • Registered Users Posts: 39,001 ✭✭✭✭Mellor

    Is the heating on? What is the thermostat set to?

    What is the air change volume per hour. Those figure should give you an idea of the work the heating and HRV are being asked to so. If there are not up to the task, temperature will drop. A HRV (without a heater) des not gain any heat, it only loses less.

    Without a heat exchange its not a HRV, so I would hope it has one.

  • Registered Users Posts: 2,823 ✭✭✭MicktheMan

    I doubt very much the ventilation system is the cause of the "freezing house".

    What type / age is the house?

    Was the house tested for air tightness?

  • Registered Users Posts: 2,569 ✭✭✭Yellow_Fern

    Did you install a heat pump? It could just be your heating system is not enough.

  • Registered Users Posts: 837 ✭✭✭keno-daytrader

    Most MHRV units will go into frost protection under 3c, I know ours bypasses the heat exchanger when this happens.

    ☀️ 6.72kWp ⚡2.52kWp south, ⚡4.20kWp west

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  • Registered Users Posts: 222 ✭✭BalboBiggins

    Thanks lads, I have a combi boiler and rads heating the house. The problem I find is that the rads will heat a room and get too hot and then when I turn off the heat, the little bit of cold air coming from the hrv vent in the room makes the room cold again quite quickly. Also it feels like there's a draft in the room due to the cold air.

  • Registered Users Posts: 2,823 ✭✭✭MicktheMan

    By the way you describe the problem, it looks likely you have an air leakage issue. That cold air you are feeling is likely from this air leakage. This is not an uncommon problem.

    There would not be enough capacity in the volume of air passing through the ventilation system to cause such a quick cooling effect.

    Was the house tested for air tightness?

  • Registered Users Posts: 222 ✭✭BalboBiggins

    Sorry for the late reply. The house is meant to be airtight but the builders who renovated it were cowboys tbh. Do you know how I should proceed with testing airtightness please?

  • Registered Users Posts: 2,823 ✭✭✭MicktheMan

    Tbh, I'm not 100% sure what you're asking. If you want a pure air tightness test then google your geographical area and "air tightness tester" and take it from there.

    On the other-hand, a heat loss survey (which includes the air tightness test amongst other things) will pinpoint where the issues are and offer various solutions depending and might be a better bet.

  • Registered Users Posts: 367 ✭✭Biker1

    If the air coming in through the vents is much lower than the room temperature when the heating is on then the starting point is your MVHR set-up. It may not be balanced correctly. Get a ventilation validator to check it for you.

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  • Subscribers Posts: 40,953 ✭✭✭✭sydthebeat

    Could your mhrv be stuck on "summer bypass" mode ?

    Therefore not recovering heat and only blowing very cold air into the rooms...

  • Registered Users Posts: 222 ✭✭BalboBiggins

    I actually turned off summer bypass in December but it didn't seem to make a difference.

  • Registered Users Posts: 22 MTK_1966

    I wonder if the device needs a service? Do people have their HRV serviced? I have a ProAir 600 device for 12 years now and I have never had it serviced. I change the filter every year but I have never opened it up and cleaned the heat exchanger. I wonder should I get it cleaned, is it something you can do yourself?