James Newport Posted July 20, 2021 Share Posted July 20, 2021 I have a room that is going to be a kitchen/diner, approximately 8.5m by 4.5m. During other works I managed to include 3 x 100mm diameter vents in the tiny eaves dead space above this room that vent out through the soffits. 1 of these is going to be used by the cooker hood, which leaves me the other two to use for background ventilation of some kind. My original plan was simply to fit a couple of low power inline extractor fans and use them to mop up any steam or cooking haze that escaped the extractor. But could I use a small MVHR just for this room instead? Would it work with both the stale and fresh air intakes in the same room? Or would I simply end up with a lovely flow of fresh air circulating between the two vents on the ceiling and not much else? Link to comment Share on other sites More sharing options...
Olf Posted July 21, 2021 Share Posted July 21, 2021 Do you have enough space in the soffits to extend the runs so they finish the recommended 1.5m apart? If not, check the 'combined grille' idea. Link to comment Share on other sites More sharing options...
Dan F Posted July 21, 2021 Share Posted July 21, 2021 I'm considering one of these two options for a garden room: - https://www.partel.co.uk/products/lunos-ventilation-with-heat-recovery - https://www.bpcventilation.com/vent-axia-hr100 Still need to look into details and costs though. 1 Link to comment Share on other sites More sharing options...
James Newport Posted July 21, 2021 Author Share Posted July 21, 2021 10 hours ago, Olf said: Do you have enough space in the soffits to extend the runs so they finish the recommended 1.5m apart? If not, check the 'combined grille' idea. Fortunately the outside vents are all approximately 2.5m apart! Link to comment Share on other sites More sharing options...
Faz Posted July 22, 2021 Share Posted July 22, 2021 For a single room I wouldn't bother with MHRV. Presumably you have got trickle vents and the like everywhere else? You need as much air tightness as possible in the house for these systems to work properly. 1 Link to comment Share on other sites More sharing options...
Nickfromwales Posted July 22, 2021 Share Posted July 22, 2021 Vent for the kitchen extractor should be 150mm if the fan is anything more than a box standard extractor. Anything less than that will remove very little from the cooking. Why not combine 2x 100mm outlets and split them off a 150 Y branch from the extractor? Use the 3rd with a damper to allow fresh air in during the summer to offset the heat from cooking. Or blank it off. Oh, and MVHR for a single room in this house will be useless. Just stick with extraction. 1 Link to comment Share on other sites More sharing options...
James Newport Posted July 22, 2021 Author Share Posted July 22, 2021 9 minutes ago, Nickfromwales said: Why not combine 2x 100mm outlets and split them off a 150 Y branch from the extractor? That is a genius idea. Link to comment Share on other sites More sharing options...
Nickfromwales Posted July 22, 2021 Share Posted July 22, 2021 5 minutes ago, James Newport said: That is a genius idea. I have my moments......usually 3-6 months apart though Link to comment Share on other sites More sharing options...
James Newport Posted July 22, 2021 Author Share Posted July 22, 2021 I would have liked full house MVHR, but the design of the place meant that a single system would have been a nightmare to get the ducting installed, plus the airtightness issue worried me. There are no trickle vents but I reckon the old blockwork walls are leaky as anything. 18 minutes ago, Nickfromwales said: Oh, and MVHR for a single room in this house will be useless Useless because of lack of air tightness? Or because the system will be trying to ventilate the rest of the entire house? Link to comment Share on other sites More sharing options...
Nickfromwales Posted July 22, 2021 Share Posted July 22, 2021 1 minute ago, James Newport said: Useless because of lack of air tightness? Or because the system will be trying to ventilate the rest of the entire house? And a bunch more reasons on top. MVHR is whole of house in a reasonably airtight house, or zilch. Flow rates are so low, infiltration ( natural ) often exceeds the design room ACH values, so essentially is just blowing past the MVHR. Retro-fit of MVHR is a complete an utter pig to get right, with a lot of build fabric amendments and also needing a very close eye on detail ( so you couldn't trust most 'general builders' to execute this on your behalf ). Link to comment Share on other sites More sharing options...
Seeoda Posted September 12, 2021 Share Posted September 12, 2021 On 22/07/2021 at 19:42, Nickfromwales said: And a bunch more reasons on top. MVHR is whole of house in a reasonably airtight house, or zilch. Flow rates are so low, infiltration ( natural ) often exceeds the design room ACH values, so essentially is just blowing past the MVHR. Retro-fit of MVHR is a complete an utter pig to get right, with a lot of build fabric amendments and also needing a very close eye on detail ( so you couldn't trust most 'general builders' to execute this on your behalf ). If your house is wet plastered and you are willing to change leaky doors/windows should be possible to get house airtight enough Link to comment Share on other sites More sharing options...
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