If you have a new account but are having problems posting or verifying your account, please email us on [email protected] for help. Thanks :)
Hello all! Please ensure that you are posting a new thread or question in the appropriate forum. The Feedback forum is overwhelmed with questions that are having to be moved elsewhere. If you need help to verify your account contact [email protected]

Ventilation options - house not airtight

  • 02-08-2022 2:22pm
    Registered Users Posts: 18


    Question on potential mechanical ventilation for a semi detached house built in 93/94.

    The house is not air tight. However we have improved things in recent years as we have installed double glazing, new external doors and have insulated the attic. We have a gas fire at the fireplace so have an anti-downdraught cowl on chimney.

    Currently we have hole in wall vents, extractor fans in bathrooms and extractor over hob in kitchen.

    Our issue is that in summer there are lots of bbqs in area and in winter there are daily coal/turf fires in area which means air quality can suffer inside house.

    There are no internal signs of issues with mould/condensation.

    We are considering options for mechanical ventilation with filters as would like to ensure better air quality. We won’t have room for ducts etc so thinking something that slots into the existing wall vents.

    A potential additional factor to consider is that on the updated radon map, we are now in a red area. We are getting the house tested for this.

    Does anyone have any advice on options for better ventilation?



  • Registered Users Posts: 507 ✭✭✭mike_2009

    Decentralized ventilation is certainly an option. Adds up in cost over a couple of units with multiple filters to swap (twice a year?). You'll still find some odours / pollution still making it inside but it will be a lot better. Most smaller units may only have G4 filters and not F7 / better.

    I fitted a MVHR unit above the stairs last year with ducts running through attic to feed the bedrooms/draw from the bathroom/en-suite. Use F7 filters. Very effective. Plan to do downstairs but will need to lift up floorboards to run ducts to downstairs rooms. Doable but tricky! Not perfect in that you can still get smells from outside.

    You'll have to see if your vent holes are big enough for the pipes the decentralized units use. Hopefully not too much core drilling involved to widen?

    The other option I tried was Positive Input Ventilation - a unit that sits above the ceiling of the landing and pushes air into the landing and creates positive pressure upstairs to keep kitchen smells downstairs. The only drawbacks are if the bbq/other pollutants get into the attic, you'll be relying on the F7 filters to deal with it. In Winter you have a heater unit which uses some electricity to warm the air below a certain temp, watch the bills and get a unit with the heater above the landing hole, not at the unit end or you'll spill heat into the attic. If it's a cold roof you'll get condensation up there, a lot, which is what I experienced. Hence the MVHR switch.

    Best of luck!

  • Registered Users Posts: 18 Jackson22

    Thanks for all of this!

    I am not sure if could do ducting through attic as it’s converted so I think it will be a search for decentralised units that have F7 filters. The vents (covers) are 9 x 6 so I am hoping that this is fairly standard and units will fit in.


  • Registered Users Posts: 2,480 ✭✭✭Yellow_Fern

    Did you test your airtightness with the vents sealed? Another thing could you do while you plan a ventilation strategy is get a airtight grade cooker duct extraction duct damper.

  • Registered Users Posts: 18 Jackson22

    I haven’t done an airtightness test.  How is this done? Does it take long? (Sorry it’s all new to me!)

    On the cooker duct extraction dampener, are they easy to source/ get installed?


  • Registered Users Posts: 2,480 ✭✭✭Yellow_Fern

    Just takes a few hours. It helps a lot. You can kind of see where you are and if you have a good tester, they can give really excellent advice. Airtightness is often more important in Ireland than insulation. The cooker damper should be easy enough to install if you live in a house rather than apartment.

  • Advertisement