Edwardian Terrace Chimneys and MVHR

[hotnuts21]

We are renovating and extending our Edwardian terrace which has 8 chimneys, 4 on either side. Pretty much every room has either a fireplace, or an air brick and two are completely blocked up (which is a bit worrying). 

We are looking at installing an MVHR unit, but I cant reconcile this with the need to let the chimneys breath or at least have airflow. Im sure we are not the first people to look at making an old property watertight and what damage maybe done to chimneys if we cap them, and if we do at which end? The extension is a timber frame and airtight structure, and as we are working through the house we are slowly incorporating a much more airtight structure to the property, with decent fitting doors/windows etc.  Internal insulation and externally the stone walls will be repointed with lime to let them breathe outwards.

Has anyone come across anyone who has capped chimneys or sealed them up and has some years under the belt with no damage inside the chimneys? Im sure blocking them at both ends could cause damp/condensation with temperature fluctuations.

Many thanks for reading.
Paul

[tonyshouse]

Off the record and without liability I have been sealing up chimneys for years, never a problem on internal walls, no air vent, sometimes filled, often take a brick out in the loft. Insulate well, and up the chimney breast in the loft

 

i think the need to ventilate them dates back to before central heating was the norm - how can a chimney structure inside a heated envelope be cold enough for condensation to form in it? 
 

caping the top needs to still allow air to circulate, they can stream with condensation if not and that can run down inside the flues 

[hotnuts21]

Thanks Tony thats interesting, when you say you insulate them, is that internally inside the chimney or just on the breast walls in the rooms?

I was wondering exactly the same thing, if we put an elephants foot on the top to stop water getting in but its still able to breathe, but then seal them up at teh room level there is still space for the moisture to evaporate if any ever got in.  I like the idea of venting into the loft space.

I did also wonder if you could vent your MVHR out through a chimney, if we install on its going to go into the old fireplace in the utility room anyway. Not sure if thats been done or not.

[hotnuts21]

Slightly off topic but I'm still amazed someone plastered the inside of the chimney over 100 yrs ago and what a good state it's in.

[Bonner]

Chimneys were often parged with lime mortar to protect the brick work, improve draw and prevent leaks. Yours does look in good condition and remarkably clean.

[tonyshouse]

Looks never used

[Wil]

In relation to this query, I also have a lot of big old chimneys and have been wondering about using them as the delivery mechanism for the MVHR. As in: 

 

Put the MVHR up in the loft with relevant supply and extract ductwork through roof. Cap the chimneys at the top, then break into the chimneys at high level in the loft. Stuff insulation up to the cap and seal the bottom of the insulation (above my break in hole). Then attach MVHR supply/ extract (internal) ductwork to the holes in the chimneys and use them as oversize ducts to the rooms.

 

Solves two birds with one stone in my case- sealing up massive draughts up the chimneys and using dead space for risers/ air supply?

[hotnuts21]

On 15/07/2021 at 08:13, tonyshouse said:

Looks never used

Indeed, there is a bit of soot in it, but not a lot. Its in what is now the upstairs bathroom, but in the past must have been a bedroom. When I pulled up the flooring the original tiles were still there too, they were very basic though.

 

On 15/07/2021 at 14:54, Wil said:

In relation to this query, I also have a lot of big old chimneys and have been wondering about using them as the delivery mechanism for the MVHR. As in: 

 

Put the MVHR up in the loft with relevant supply and extract ductwork through roof. Cap the chimneys at the top, then break into the chimneys at high level in the loft. Stuff insulation up to the cap and seal the bottom of the insulation (above my break in hole). Then attach MVHR supply/ extract (internal) ductwork to the holes in the chimneys and use them as oversize ducts to the rooms.

 

Solves two birds with one stone in my case- sealing up massive draughts up the chimneys and using dead space for risers/ air supply?

Interesting, I have been wondering about using the Chimney flues to run the pipework through but not sure if its viable. Not sure I trust they are air tight enough all round to just use room ducts.  I did wonder if I could use them for the incoming and outgoing air sources for a mvhr though.  

At the moment all our quotes are coming in at around 6k for MVHR and with such an old and draughty house its not worth it, but I think it will be in the future as we slowly seal everything up. But nows the time to run in the ducting and no one seems interested in a two stage approach.  Its just one of many nightmares I have going on at the moment where im not sure what to do and where to spend the money ?

Thanks for al the tips/advice guys.  I might try photographing all the chimney flues eventually (we have 8).

 

Paul

[dom0_o]

Hi Paul,

Just found this tread and I am going to be getting a Edwardian house with lots of chimneys and was wondering what you did with this in the end?

Dom.

[hotnuts21]

On 27/05/2022 at 10:57, dom0_o said:

Hi Paul,

Just found this tread and I am going to be getting a Edwardian house with lots of chimneys and was wondering what you did with this in the end?

Dom.

I'm still tearing my hair out about it!

One thing that might be obvious but wasn't to me, is that MVHR essentially just moves air around the house, by extracting it from the kitchens/bathrooms/utilties etc and then using that to warm air being pushed into the bedrooms/lounges. So if the rooms your pulling from are air tight and warm, then pushing warm air into draughtier rooms is less of a problem (than pulling it from the draughty rooms). 

For some of the rooms im going to seal the chimney up, and then knock through in the attic space to allow for some level of circulation, im also going to vent from my suspended ceilings into the chimneys so air can come in through air bricks and up the chimney, with the chimney and floor being sealed from the rooms so essentially making the room airtight but the voids have a airflow. Also insulating those floors.

I haven't settled on a MVHR yet, ive talked to a lot of companies but they seem to gloss over the fact its not airtight, but then quote airtight standards to me, they are also all mega busy, 2-3 months before enquiries are being answered. Essentially though I'm looking at ones which can run at 40% capacity for now, so we can do the back half of the extension house extracting with no problems, and then turn up it up as we add rooms. As it happens, utility, kitchen and 2 of the 3 bathrooms/WC are all in the new build so thats easy enough for us.

I'm still totally open to option though 🙂

[SBMS]

1 hour ago, hotnuts21 said:

I'm still tearing my hair out about it!

One thing that might be obvious but wasn't to me, is that MVHR essentially just moves air around the house, by extracting it from the kitchens/bathrooms/utilties etc and then using that to warm air being pushed into the bedrooms/lounges. So if the rooms your pulling from are air tight and warm, then pushing warm air into draughtier rooms is less of a problem (than pulling it from the draughty rooms). 

For some of the rooms im going to seal the chimney up, and then knock through in the attic space to allow for some level of circulation, im also going to vent from my suspended ceilings into the chimneys so air can come in through air bricks and up the chimney, with the chimney and floor being sealed from the rooms so essentially making the room airtight but the voids have a airflow. Also insulating those floors.

I haven't settled on a MVHR yet, ive talked to a lot of companies but they seem to gloss over the fact its not airtight, but then quote airtight standards to me, they are also all mega busy, 2-3 months before enquiries are being answered. Essentially though I'm looking at ones which can run at 40% capacity for now, so we can do the back half of the extension house extracting with no problems, and then turn up it up as we add rooms. As it happens, utility, kitchen and 2 of the 3 bathrooms/WC are all in the new build so thats easy enough for us.

I'm still totally open to option though 🙂

One thing to remember is that ideally your ductwork needs to be within the heated envelop of the building, or you need to make sure that your supply/extract ducts are well insulated in the chimney void - or that you insulate the chimney void before installing the ductwork. 

[hotnuts21]

15 hours ago, SBMS said:

One thing to remember is that ideally your ductwork needs to be within the heated envelop of the building, or you need to make sure that your supply/extract ducts are well insulated in the chimney void - or that you insulate the chimney void before installing the ductwork. 

Thanks, yes thats true, im not sure using the chimney voids is that realistic but I will continue to investigate all options. Thanks 🙂

[Remington]

Could the chimneys be treated like how a stove liner would be installed - so a duct pipe down the chimney, a register plate at the room entry point and the rest of the gaps in the chimney backfilled with insulation beads?