Gone West Posted March 1, 2018 Share Posted March 1, 2018 To get the house signed off I set up our MVHR for Building Regs. PH ventilation rates are very different to Building Regs so I am thinking of resetting the MVHR to give PH ventilation rates. Is that what other low energy house builders have done? Link to comment Share on other sites More sharing options...
Gone West Posted March 7, 2018 Author Share Posted March 7, 2018 Are there any thoughts about the different methodologies used between PH and BR ventilation calculations? Please. Link to comment Share on other sites More sharing options...
Jeremy Harris Posted March 7, 2018 Share Posted March 7, 2018 On 01/03/2018 at 15:52, PeterStarck said: To get the house signed off I set up our MVHR for Building Regs. PH ventilation rates are very different to Building Regs so I am thinking of resetting the MVHR to give PH ventilation rates. Is that what other low energy house builders have done? It's exactly what I've done, Peter, and I've read of others doing the same. PH rates seem pretty close to being the sort of ventilation rate we're comfortable with, in fact I'm tempted to turn the background rate down a little bit more, as there are only two of us in what is a fairly high volume house. My understanding (I could be wrong) is that the building regs rates were set to be sure of having sufficient ventilation to remove volatiles given off by furnishings etc, in pretty much the worse case. I would lay money that the MVHR ventilation rates in the regs are massively greater than the real-world ventilation rates for a standard leaky house with just window trickle vents open. 2 Link to comment Share on other sites More sharing options...
joe90 Posted March 7, 2018 Share Posted March 7, 2018 I am not yet at this stage but have already thought that I would set the MVHR as I want it but make up the figures to keep the building inspector happy, there is no way he will challenge it anyway ? ( I have a copy of Jeremy’s spreadsheet). 1 Link to comment Share on other sites More sharing options...
Alex C Posted March 7, 2018 Share Posted March 7, 2018 With my MVHR the house meets building regs if you turn the control to 3 out of 3. We are a family of 4 in quite a high volume house and have found we can run it at 1 which is I think lower than passive house level. We never even use boost as there is only ever steam in bathrooms if the kids have long showers one after the other and this quickly disappears. House is approx 700m3 and I set the extract at 100m3 per hour. The figures given to building control were with fan set at 3. They didn't question it at all. I have a number of humidity sensors and these show a pretty constant 45% and dropped down to 35% over the cold dry weather we had recently.This would suggest there is no problem with humidity build up even with low extraction rates. It never ceases to amaze me how quickly washing dries in the house. There is no point whatsoever in having a tumble drier. 1 Link to comment Share on other sites More sharing options...
jack Posted March 7, 2018 Share Posted March 7, 2018 Similar here. 289m2 house, four occupants (and a doggo), and we run the MVHR at 80m3 per hour. In fact, we ran it at 50m3 per hour for the first year we were here and have never had any issues with moisture or air freshness. I think the critical thing is that the air is being refreshed continuously, even when we're out, or there's only one or two of us at home. There's no boost when people are having showers, and steam clears away very quickly. The only time I turn it up is if we're going to cook something smelly or we have a lot of people over and need more fresh air. 1 Link to comment Share on other sites More sharing options...
Stones Posted March 7, 2018 Share Posted March 7, 2018 Our house has a volume of 475m3 and we ventilate at around 115m3/hr. We have found in previous houses that below 20% of house volume starts to cause problems in terms of air quality and condensation. 4 of us in the house, so it may well end up being a lower figure as and when the kids leave home. 1 Link to comment Share on other sites More sharing options...
MJNewton Posted March 8, 2018 Share Posted March 8, 2018 On 01/03/2018 at 15:52, PeterStarck said: PH ventilation rates are very different to Building Regs [..] Do you have a link to what the PH rates are? Link to comment Share on other sites More sharing options...
le-cerveau Posted March 8, 2018 Share Posted March 8, 2018 PH recommends approx 30m3/h per person, which results in lower that Building Regs rates. 1 Link to comment Share on other sites More sharing options...
Alex C Posted March 8, 2018 Share Posted March 8, 2018 Interesting read about air changes and humidity levels in Passive houses 1 Link to comment Share on other sites More sharing options...
Gone West Posted March 8, 2018 Author Share Posted March 8, 2018 1 hour ago, MJNewton said: Do you have a link to what the PH rates are? I can't find the link at the moment. For extract I used 2 ACH for bathrooms, 0.7 ACH for the kitchen and 1.1 ACH for the utility room. For supply I used 0.4 ACH for bedrooms, 0.5 ACH for reception rooms and 0.3 ACH for the hall. This gives a balanced total of 101 m3/h on fan speed 2, which can be reduced by using fan speed 1 and adjusting the fan speed percentage accordingly. 1 Link to comment Share on other sites More sharing options...
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