Part F vs PHPP Ventilation

Clseeper

I’m pre build and doing my meticulous research and modelling of the proposed build (DEAP, PHPP, THERM etc). I’ve gotten onto my ventilation system and have noticed a massive difference between the recommended PHPP ventilation versus the building guidelines Part for my home.
For my floor area (245m2), Part F tells me I need a minimum of ~264m3/hr but working off the PHPP sheet it states I only need 180m3/hr supply (160 extract). If I run the ventilation unit at the required level to supply 264m3/hr, PHPP starts throwing up warnings (dry air risk etc). I can see from PHPP sheet it aims to keep the ach between 0.3 & 0.5.
So a few question from this;

1. Which method is following international best practice? Why the big difference?
2. Obviously I will be complying with Part F but will I need to design in some remedial action to address PHPP warnings and ensure good indoor humidity? (plants, open water etc)
3. How much of a guard band are these ventilation systems normally speced to? Will my installer balance the system at the Part F min and then I never go near it again apart from servicing?

fclauson

Clseeper wrote: »

So a few question from this;

1. Which method is following international best practice? Why the big difference?

I struggled with this - Maurice Falvey of Nilan did some research modelling a house for 2 years and concluded that Part F is what is required in Ireland.

I also read up on this and concluded the same - despite thinking otherwise - I vent at Part F and its fine - the humidity oscillates between 40 and 60% (remembering a typical day in Ireland can be in excess of 90%)

1. Obviously I will be complying with Part F but will I need to design in some remedial action to address PHPP warnings and ensure good indoor humidity? (plants, open water etc)

wait and see - I thought this but have not needed to

1. How much of a guard band are these ventilation systems normally speced to? Will my installer balance the system at the Part F min and then I never go near it again apart from servicing?

- do you never service you car either - do you own checks and then keep an eye all the time on the system - I have just maintained mine after 1 year - little bit of dust on the fan blades etc. plus new filters

Clseeper

Fclausen,

Thanks for the reply. I had a feeling I may be walking an already worn path. I've actually been in touch with Maurice and gotten some good information and a copy of his slides from the 'See the Light' conference. They do show the house data for the last two years at or around 50% RH also. This along with your results are helping to allay my fears - thanks.

WRT to the intervention rates on the MHRV system - I probably should have phrased my question better, sorry. I was wondering how much manual input/compensation would be needed (manually changing fan speeds etc) on a week to week basis depending on external %RH. This was based on the assumption that I may have an overly dry air environment by meeting Part F - which doesn't seem to be the case, so possibly not a problem. Obviously I'll be keeping an eye on everything and getting to know the different hums & squeaks intimately

The guard band reference should have been phrased more like - do most building perform at Part F or should they nominally be delivering 10/20/30m3/hr more. A bit like the insulation guidelines where they say minimum 0.21 for walls but we know it's better to go lower (much lower ). So from the data it seems minimum the Part F value is the target as opposed to real minimum. This does make sense due to the two different ways to calculate the required min. One being the possibly more scientific way (x litres per person) and then the catch all for the very large house (x litres per area). The fact that my house is on the large side - I'm in the catch all bucket.