Continuous ventilation rates can be much lower than extract fan rates as all the time ventilation does more good, keeps the air inside nice.

0.6 ach sounds OK to me but there should be boost facility of say 1.0 -- some people run at lower rates than 0.6 I think I do 0.5 during the day and 0.4 other times with 0.6 only sometimes, showers, cooking, more people here.

Paul usually knows the answers better than I do

You would be better to measure the actual ventilation rates as bends in the ducts, undersized ducts will slow down air flows and it sounds like yours are well low to me.

And how many m3 is your house? You should buy a humidity monitor?

.

But the air leakage is only that bad when when the wind is 20mph+!. Only joking.
Seriously, I have seen Paul comment, previously, that the whole house ventilation rate should be 30m3/person with 10L/s for a living room inlet etc. Others have suggested that a large airy house with few occupants is not subject to the same tight adherence to regs as a smaller home with many occupants.
In my own refurb - moderately improved 124m2 1930 chalet bungalow, 2 adults- I manage very well on a whole house ventilation rate of 70m3/hr; regs require a minimum whole building ventilation rate of 134m3/hr (with no allowance for infiltration). Your rate is exactly right for the minimum value of 0.3L/s per m2 of floor area; again not allowing for infiltration.
Your house is very large with a lot of moisture of construction. Have you adopted any of the suggestions to put your room temperatures up and/or use dehumidifiers for a while?

Have you given us any actual measured ventilation rates yet? or only theoretical ones?

Air leakage of 151 is presumably at 50 Pa ? -- This is uncontrollable = zero on calm days and higher but not 151 on windy days.

Brogie 2805,
so is your MVHR running at maximum the whole time ( to give the minimum whole house ventilation rate)?
If so, I would expect it to be rather noisy. Assuming that you have 8 outlets for incoming air that would be an average of approx 15.5L/s per outlet. At that level I am sure that draughts would be noticeable; they certainly would be on my 125mm air valves.
Is there a brisk airflow at the outlets and noticeable air movement at a distance of 1metre?

Do you mean the following?

outside temp = 3 celcius
EXHAUST air temp = 6 celcius
supply air temp AFTER HEATING COIL = 27 celcius
EXTRACT air temp = 14 celcius
supply air temp BEFORE HEATING COIL = 13 celcius.

If so then these numbers look reasonable for a house with no heating or heating to only part of the house. Is the heating coil the only means of heating? Are you heating some parts of the house & not others?

In general, when using whole house heat recovery ventilation you should heat the whole house to the same temperature. This is especially important when the house is drying out.

David

What's the temperature in the house? What is the Humidity these days?
You need 350m3/hr to meet part F and you have 280m3/hr which is probably ok.
Open the windows for 20 mins tomorrow and give it a good airing.

Brogie 2805,
Part F regs in England for larger properties seem to result in a disparity between Whole Building Ventilation rate based on bedrooms and occupancy with an infiltration allowance subtracted, based on volume, versus the minimum rate based on internal floor area.
The latter gives the value of 453m3/hr which overrides the former at 117m3/hr. In practice, my experience has been that with low occupancy and a careful lifestyle, ONCE YOUR HOUSE IS DRY, your MVHR may be up to the job running at moderate speed.
My rate of 70m3/hr is actually OFF on my 350m3/hr maxm unit; this is meant for background ventilation when the house is unoccupied e.g. holidays. The larger unit also gives a better pressure/flow characteristic curve; my refurb forced tortuous runs of smaller ducts than I would have wished i.e. higher resistance to overcome in the ducts. We rarely ever switch to a higher rate; this includes the times when we open the MVHR cooker hood.
Regards, Martin.

Posted By: brogie2805This is the temperatures on the handset with the boiler stove pumping, and suppling the heating coil:
outside temp = 3 celcius
extract air temp = 6 celcius
supply air temp = 27 celcius
exhaust air temp = 14 celcius
supply air temp after rotor = 13 celcius.

Posted By: brogie2805I wrote it exactly according to the technical booklet supplied with the unit, there are two wood burning stoves, one 10kw (8kw to boiler which goes to the heating coil and 4 towel rails), and the other is a 5kw stove. We have 1500w oil filled rads in the parts of the house not being used to aid heating. The coil is supposed to be able to deliver warmed air at 40 celcius at all inlet valves however the temps in the bedrooms vary from 10 to 18 celcius?

If the above temperatures were correct then the MVHR unit would be extracting air from the wet rooms at 6 Celcius & supplying air to the heating coil at 13 Celcius, while exhausting air at 14 Celcius towards the outside. This just isn't possible in a correctly configured & commissioned system. If this is what the controller says then either the temperature sensors are cross wired or the ducts are cross plumbed. For the moment, lets just assume the technical book got it wrong.

Posted By: brogie2805Temp varies throughout the house Viking from 20 to 10 degrees, humidity varies also from 55 to 85%, Environmental health carried out inspection today and was of the opinion that the ventilation running at standard level is not adequate for the house.

It may be that the MVHR is not quite up to the job, but that is not why you have damp & mould problems.

If the air at the extract terminal of the MVHR is at 14 Celcius then the average temperature of the air extracted from the wet rooms is 14 Celcius. In other words, the only air stream which is carrying moisture out of your house is at 14 Celcius. Air at 14 Celcius can carry around 50% less moisture than air at 20 Celcius. In addition, if this average is achieved by warm moist air at 21 Celcius mixing with air at 10 Celcius then you will get condensation problems in the ducts which could lead to mould growth.

So, for the moment, I would forget about the MVHR & look at ways in which you can get an even 20 Celcius through the whole house by moving the oil filed radiators to the coldest rooms & running stoves continuously on low if necessary. On warmer drier afternoons, open all the windows for 20-30 minutes & then re-heat the house to 20 Celcius until the damp starts to dissipate or the summer arrives.

If you're unable to get the whole house to 20 Celcius then move your focus to the heating coil. What temperature/flow rate of water does it require? What air flow rate does it require? Are the air supply terminals balanced? Are the air supply ducts insulated? Are all the ducts inside the heated envelope of the house? Do any of them pass uninsulated through the rooms which are at 10 Celcius?

As long as you keep the whole house at 20 Celcius then you're unlikely to have problems with the MVHR. If you only heat some parts of it then whole house heat recovery ventilation is not the right solution.

David

Posted By: tonyI think it is saying outdoor air = 3C; air leaving unit and going out of house 6C; air coming in after heat exchanger 13C heated to 27C and going to rooms; air extracted from rooms 14C

Agreed.

David