Retrofit MVHR feasibility (chimney ducting) and aesthetics in period house

[NCXo82ike]

Hi all, 

 

This forum has been an amazing source of information as I plan our retrofit of a mid-terrace Victorian property. I'm not looking at MVHR. We are planning extensive renovation-  substantial energy performance upgrade and ASHP alongside the decorative side.  I highly doubt we would get any payback from MVHR, even given given my plan to buy cheap/second hand and DIY most of the install.

 

The house has no mechanical ventilation as original including the bathroom and kitchen. The default, and budget) option would be wall or inline extractors. Trickle vents and PIV are other options I'm keeping in hand.

 

The motivation is humidity regulation, meeting building regs including (rooms-within-rooms), and above all comfort. Despite original sash windows throughout, we still crack open the bedroom window overnight with a noticeable benefit to air quality. This problem will be worse post-renovation. 

 

I've attached the existing floor plan. We plan on wrapping around the kitchen so the rear will be warm and air tight. We plan on converting the loft to a dormer, possibly L shaped and the joist layout/type can be adapted to accommodate services. There will be eaves space which could house the MVHR above Bed 3 and in the eaves at the front next to the new master bedroom. The house will therefore be 4/5 bedrooms over 3 storeys with 1 kitchen, 1 cloakroom, 1 utility, and 2 bathrooms requiring extraction. About 160-170sqm in total. The chimney breast in the offshot is coming out. Those in the main portion joint to a single stack in the roof void.

 

I have a few key questions which I hope someone can help with based on my planned installation of a radial ducted system:

 

1. Is there any reason not to run semi-rigid radial ducts through the chimney stack in the main house? None of the fireplaces are in use. The chimney is currently uncapped but I would like to cap it and effectively turn it into a warm space to reduce heat loss and avoid condensation problems. I could run ducts through the loft floor, punch through the chimney breast, and drop down to the 4 rooms below. I can create a sizeable void next to the bathroom which lines up with the utility, creating a centralised. service stack
2. Are there any decorative supply valves? I'm considering mounting the supply in the chimney breast but the round ducts would not ideal there or in the roof. Square plaster vents (as in the attached image) would fit better aesthetically, perhaps with balancing valves at the MVHR unit end?
3. Would the entry/atrium be better as an extract to improve air flow through the other rooms such as the sitting room?
4. Any thoughts on the alternatives for MVHR unit placement? I'm tending towards the eaves next to Bed 4 for noise reasons. This has access to the rear wall and roof for extract/supply. The eaves at the front would require supply/extract through the slate roof (which we are re-roofing regardless)
5. I presume it makes sense to bring the eavches within the thermal envelope regardless- whether for MVHR or storage?

 

Many thanks in advance.

Edited April 6, 2021 by NCXo82ike

[Sparrowhawk]

@NCXo82ike Did you install ducting in the chimney stack in the end? I've been thinking about this for our house so your experiences would be good to hear.

[NCXo82ike]

45 minutes ago, Sparrowhawk said:

@NCXo82ike Did you install ducting in the chimney stack in the end? I've been thinking about this for our house so your experiences would be good to hear.

Still waiting on planning permission...

 

But still planning on installing the ducting in the chimney at the front of the house.

[denright]

On 25/09/2023 at 12:57, NCXo82ike said:

Still waiting on planning permission...

 

But still planning on installing the ducting in the chimney at the front of the house.

 

Very interesting post! How did you get on with these plans since?

[NCXo82ike]

6 hours ago, denright said:

 

Very interesting post! How did you get on with these plans since?

4 years on... Finally have planning and hope to build this autumn. 

 

The plan is still to sit the MVHR I'm the eaves. We'll use ended joists to convert the loft and run ducts through those.

[JohnMo]

On 06/04/2021 at 20:12, NCXo82ike said:

I'm not looking at MVHR

 

On 06/04/2021 at 20:12, NCXo82ike said:

Trickle vents and PIV

 

On 06/04/2021 at 20:12, NCXo82ike said:

radial ducted system

Sorry a bit confused are you looking at MVHR or PIV?

 

Unless you are going to make a serious effort on airtightness MVHR would be a none starter for me, you are just adding additional ventilation heat losses.

 

I would also ditch PIV, you are effectively blowing in cold air in winter and hot air in the summer at an almost constant rate.

 

I would do either dMEV or MEV. Either would be run based on air condition, so humidity based.  The inlet to the system would be self modulating either trickle vents or though wall vents in the dry rooms only. Extract would be either ducted (MEV) or through wall/eaves fan (dMEV). Pretty simple to install, minimises heat loss.