Critique my MVHR Design Please!

[maninsheds]

Hi All

 

I'd appreciate a critique of my MVHR design before I start making holes in things. 

 

This is a retrofit to a 1850s cottage with later extensions. Major refurb and retrofit 6 years ago, but didn't fit MVHR at the time (didn't back myself to get the airtightness low enough at the time, but turns out its just below 1 so its very under ventilated at the moment) 

 

Already bought a Vent Axia Sentinel B. 

 

Thinking it will be a radial system mainly in 75mm semi rigid, but there are few places where i will switch to round galv or rectangular duct due to aesthetics/ space constraints. 

 

Particular queries are:

1)  Lots of constraints to duct routes as you'd expect, so some of the vent locations are none ideal, but I've done my best. Any heads up on those that may be problematic would be great. 

 

2) Sense check of my ventilation rate calcs would be good. From what I've worked out, in order to supply the necessary air, I'm going to meet the extract rates anyway so theoretically wouldn't need a boost mode for part F. I'm guessing this is not unusual though? Will add a boost switches / humidistats in bathroom and kitchen anyway. 

 

3) Duct speeds all look ok and calculated correctly?

 

4) Is the Vent Axia B suitably sized? Not to late to change my mind if there is anything I've missed. 

 

Also not yet done my research on silencers etc. Sure there is stuff on here and elsewhere I can read up on, but any quick tips on what I should incorporate if anything would be great. 

 

Flow calcs etc here:

https://docs.google.com/spreadsheets/d/1Y-T45Mv2AB6M5k68rblZWlrH_XpvLbt0rz_p5l3Jelc/edit?usp=sharing

 

Planned Layout here:

MVHR Layout v2.pdf

Thanks in advance

Dan

[JohnMo]

Not sure the location of the kitchen extract is good above the hob. I would bin supply in the dining area and make that the extract for the kitchen.

 

Secondary air for the stove being pulled from the room, could depressurise the room, allowing fire fumes to enter the room, so you need to be careful.

[maninsheds]

Thanks, I was a bit concerned about extract being so close to hob. (grease being my main concern) Anyone experience of using grease filters for an extract point close to a hob. 

 

My concern with doing as you say and using the dining area point as the extract is that the air flow might just do the below, and not properly ventilate the areas of the kitchen where the moisture is being created. But that might just be a theoretical concern?

 

 

 

[JohnMo]

I would think it's more likely to do this. A ceiling extract terminal, will pull the air across the whole room

 

The extract above the hob will throw the air across the room in red.  The blue lines will pull that air and the air from the supply to the dining area and the downstairs toilet.

 

[MJNewton]

We've got an extract above the hob and it works well - helps ensure steam and cooking smells are removed at source. Did think we might have an issue with airborne grease and so fitted a washable sponge filter inside the vent but we don't do all that much frying so I wonder how much we really require it. The extract is double ducted and we have two single ducted supplies at opposite ends of the open plan kitchen/diner/lounge.