Any thoughts on the following ventilation/moisture control system?

(Note - the house will have better than B Reg insulation regulations and mid range air tightness – on a “just in case” basis)

- A PIV unit taking air from the loft or direct from the outside then preheated to 10 or 15 deg
- Two Cyclone extract fans in the main use bathroom and kitchen
- Normal extract ventilation in the other bathrooms or Heatsava units

The configuration above meets Building Regulations Part L and while it doesn’t improve air quality only air circulation I would have thought that it would be possible to add on some kind of air cleaner without a lot of trouble. Also have a look at www.mdpi.com/2075-5309/3/1/61 A Natural Ventilation Alternative to the Passivhaus Standard for a Mild Maritime Climate and the recent NHBC study on MHVR

Having the air input up high on an upstairs landing will mix up the rising warm air from the central heating system (and also from the sealed wood burner)

Moisture extraction happens in the rooms that need it most

No heat recovery but reference is made to the conclusions of the above study;

“in climates with mild winters and cool summers the use of MVHR could be omitted without compromising comfort levels and achieving at least equivalent energy savings resulting from adopting the Passivhaus model and at a lower capital cost. This suggests the potential for a naturally ventilated, ultra-low energy model with lower capital investment requirements and lower disruption when applied to retrofit that would facilitate its mainstream adoption”

The above equipment is made by Envirovent and would cost in the region of £1,500 plus VAT fitted
(I have to say that Envirovent came back immediately with helpful suggestions and costs - none of the trying to sell more expensive systems, being coy as to costings etc)

I'm sure there are plenty of detailed holes in the above but that isn't the point. I'm trying to obtain the major advantages without the cost and aggravation of a full MVHR system

Have you had a look at the Viking House "Breathing Window"? it's a ductless MVHR system so it requires you to ventilate between rooms and relies on partial pressure to equalise CO2 & H2O vapour. It's about £1000 for a single unit but can be fitted very easily and depending on the size of your house you may get away with one.

Positive input ventilation requires outlets (typically trickle vents) in all habitable rooms to ensure air circulation. These lead to draughts which, in a low energy house, are very noticeable.

David

I don't understand how it can meet Building Regulation requirements without a Heatsava in each habitable room which is not on a path from the ventilation inlet to an extract point. How many rooms fall into this category? How many Heatsavas do they say you will need?

David