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On 31/10/2022 at 23:53, irnbru said:

Hello everyone! Thank you for letting me join this fantastic community! I am currently doing a university project related to passive house. I am responsible for ventilation part. Cheers!

 

 

This paper will be useful to you https://www.passivhaustrust.org.uk/UserFiles/File/research papers/MVHR/2020.04.27-The Case for MVHR-v7 new cover.pdf

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  • Getting good air tightness is mostly down to attention to detail in the build, taping and sealing everything, and not leaving anything unsealed, no unwanted holes, design out "leaks" like cat flaps an

  • I think MVHR systems are designed to produce a target ACH (building regs use L/S) ignoring any provided by infiltration. On a calm day for example there could be very little. The 0.6 ACH figure is for

  • Hello everyone! Thank you for letting me join this fantastic community! I am currently doing a university project related to passive house. I am responsible for ventilation part. Cheers!

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21 hours ago, Adrian Walker said:

In conclusion the paper says

 

"There is no clear up-to-date evidence behind the rule of thumb that says MVHR is inappropriate for dwellings with air permeability above 3m³/m².hour @50Pa. This analysis has shown that MVHR systems result in improved ventilation and lower carbon emissions for all levels of airtightness. There is a compelling case for MVHR systems to be fitted in all new dwellings and to be strongly encouraged in retrofits where significant reductions in energy demand are being targeted.?

2 hours ago, Adrian Walker said:

In conclusion the paper says

 

"There is no clear up-to-date evidence behind the rule of thumb that says MVHR is inappropriate for dwellings with air permeability above 3m³/m².hour @50Pa. This analysis has shown that MVHR systems result in improved ventilation and lower carbon emissions for all levels of airtightness. There is a compelling case for MVHR systems to be fitted in all new dwellings and to be strongly encouraged in retrofits where significant reductions in energy demand are being targeted.?

This comes down to cost efficiency. My house is made of rice paper and has an air tightness of 3.6 as tested. The air blows in everywhere. An MVHR would be as pointless as that coffee machine or sound system the builders thought more desirable than bumping up the insulation back in 2016 when they had a go at building the house. 

3m³/m².hour @50Pa and 3 ACH are not the same thing (something I forgot earlier)

The first is based on total area and the other is on total volume if I remember correctly.

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