MVHR vs PIV + dMEV

[jayc89]

I've been mulling over the idea of installing an MVHR unit in my retrofit. The unit would have to go in our (cold) loft space (insulated ducts above the loft insulation), but without ripping up the first floor joists, routing the ducting down to the ground floor is turning into a PITA. I'm installing IWI at the same time, which will include a service cavity, so in theory, the ducting for the ground floor could run through that, but it means I'd need a ~ 100mm service cavity on top of the space lost by the IWI. All of a sudden, I'm losing a chunk of my floor space.

 

I'm beginning to think an MVHR is possibly a step too far in my renovation, so I'm looking for other solutions. We'll eventually make the house larger, so will need to comply with building regs, in that section of the building, and I really don't want to resort to trickle vents.

 

Would a single PIV in our landing, with dMEV units in all wet rooms + kitchens be a viable solution? I.e. would that provide sufficient ventilation to all rooms, plus comply with Building Regs in the extension when we get to it (based on current regs, of course...)?

Are there any better options?

[ProDave]

You just need one service riser area, which usually can be in the back of a cupboard or wardrobe.

[JohnMo]

Go on to sites like the one for FRESH-R and see how they implement MVHR.  Very few inlets/outlets.  Same thing can be done with MVHR with a little thought.

 

Also look at condition based dMEV.  only venting when required by internal humidity levels.

[jayc89]

1 hour ago, ProDave said:

You just need one service riser area, which usually can be in the back of a cupboard or wardrobe.

 

That would only work if the ducting could travel between the first floor joists everywhere else though, wouldn't it? We have solid joists and solid brick internal walls between all rooms, making that more difficult. We could core drill through the walls in between the joists though? I suspect that would mean we'd need a couple of service riser areas though, given the ducting couldn't cross joists to reach other rooms. 

 

 

[S2D2]

2 hours ago, jayc89 said:

Would a single PIV in our landing, with dMEV units in all wet rooms + kitchens be a viable solution? I.e. would that provide sufficient ventilation to all rooms, plus comply with Building Regs in the extension when we get to it (based on current regs, of course...)?

I use this setup to good effect. It depends on airtightness, ours is too poor to warrant MVHR running costs (probably, based on many assumptions...)

 

Unsure on building regs, our last house was a new build with PIV and no trickle vents so it's possible.

[jayc89]

Having a look at this evening this evening, if I were to install MVHR (the unit would be in the loft), the first floor is simple as all ducting would just drop down from the ceiling. Ground floor, right hand side is also simple, as the ducting can come through the airing cupboard above to service the Study and Snug, but it's the left hand side of the ground floor which is troubling me; I need an extract duct for the W/C and a supply duct for the Boot Room and Dining Room. 

 

 

One solution might be to drop the ducting down the wardrobe in the dressing room above Bedroom 3, but given I need to supply 2x rooms and an extract, it would be quite bulky.

 

Can anyone see any other solution that I'm missing?

[Radian]

Could you create a small space between your back to back showers and drop down into the WC, Boot room and formal dining on that line below?

[Iceverge]

@Radian beat me to it. 

 

Just hide them in the stud walls. 

[Radian]

1 minute ago, Iceverge said:

@Radian beat me to it. 

 

Just hide them in the stud walls. 

 

To make the idea a bit clearer, here it is shown in thicker green bits:

 

[jayc89]

That could work. We're not putting in the 2x new showers until the extension is up, but we are fitting IWI to the existing rooms prior to that so I could fit the ducting in the floor void just leaving an up-stand to join beneath where that stud wall will eventually be fitted. 

[Radian]

17 minutes ago, jayc89 said:

That could work. We're not putting in the 2x new showers until the extension is up, but we are fitting IWI to the existing rooms prior to that so I could fit the ducting in the floor void just leaving an up-stand to join beneath where that stud wall will eventually be fitted. 

I forgot to put a vent position in the boot room - on the run between WC and Dining room, but I'm sure you already spotted that.