MVHR Layout - Renovation Thoughts

[beddows_s]

Hello everyone.  After doing a lot of searching on the forum for others designs and solutions I thought I'd reach out and see if anyone had any thoughts on my layout proposal.  Hopefully i've captured other peoples recommendations 

 

This is going to be a retrofit to a Victorian property, we aren't sure of the exact date of construction but its circa 1830-40's.  Solid wall construction (500-600mm) with mostly lath and plaster internally.  There is no wall insulation at present but we are planning to install breathable EWI when we have the property lime rerendered over the next couple of years.  There is up to 500mm of fibre loft insulation.  We are currently in the process of carrying out renovations with the ensuite and kitchen being the first items to be improved on.  The attic isn't easily accessed and the high ceilings (3.4m in the kitchen and 3.0m in the other rooms), together with a glass veranda mean that access is tricky.  With this in mind a centralised system makes more sense (only one set of holes to try and form) and the added ventilation and filtration will hopefully provide improvements for my wife who suffers from chest issues regularly.  I know that we wont necessarily reap all the benefits of MVHR having a less than air tight property but as i can do all the installation myself feel the non-financial benefits will outweigh the extra cost over MEV for instance. 

 

I've reached out to the usual suspects and whilst I've received some designs and proposals none of them have managed to fully appreciate what we are working with; wanting to place the unit in the attic for instance even though there is no way to do it. 

 

The actual mvhr unit (vent axis plus B - due to having horizontal entry and exit ducts) will be located in a double wall unit (1200mm wide) on top of tall side by side fridge / freezer units.  This will allow me to have a straight duct line to the outside wall and probably utilise one of the combi inlet / outlet external grilles onto a north facing wall.  i'll then have a small horizontal duct run which branches to supply a small d/s manifold and also up to the attic to feed the main manifolds. Like the below:

 

The whole dwelling rate dominates the ventilation requirement and we will need 60 l/s.  I've used one of the spreadsheets available on other posts to do some duct run calcs and for most rooms twin 75mm ducts keeps velocities down below 2 - the kitchen and dining room slightly higher. So in terms of layout I'm thinking of the below:

 

Be interesting to hear your thoughts so i can move on with final shopping lists.  The manifolds shown in the attic i think i will move closer to the central wall thereby having the individual rooms ducts closer to equal lengths where possible.  Unit to manifold would be about 9m and then max duct room to the utility 15m. 

 

Thanks Scott