old house ventilation

[carlos]

we live in old stone cottage that is cement rendered inside and out, 

it is has a lot of condensation in the corners etc , this is leading to mold patches.

i didnt dryline it as there seemed to be so many conflicting opinions on how to do it properly.

so iam thinking ventilation... my question is has anyone experience with modern mev systems or heat recovery systems??

i know these are aimed at more modern airtight houses but wondered if they may be of benefit to our house.

thanks carl 

[GarethM]

Removing the render will be the best option, start on the outside and replace with lime render as that's breathable and will be damaging the mortar and timber. If it anything like our old farmhouse you'll have rotting timber and all manner of bugs eating the damp timber.

 

If that does the trick you might get away without doing the interior, dehumidifiers do help but you need to let the brickwork breath.

[Woodworks]

Not got MVHR but we do live in a 200+ year old stone barn.

 

We did dry-line the whole place with insulation inside of that. We literally tanked the whole place like it was a basement so any water that penetrates the walls does not get into our living space. Recognising old walls need to breath we lime pointed the whole of the outside. It works and has done for 10 years. Not totally mould free as there are few thermal bridges that have slight issue and the north facing bathroom. The rest of the place  is spot on in spite of our climate which may not be as bad as parts of Ireland but is pretty darn soggy by English standards (Dartmoor)

[trigger_andy]

17 minutes ago, carlos said:

we live in old stone cottage that is cement rendered inside and out, 

Bloody hell. 😳😬

[GarethM]

Just need gas tight metal doors and you've got yourself a fall out bunker!.

[carlos]

thanks for the replies, id agree that the proper job would be to remove all the cement render and lime plaster inside and out, but dont really fancy doing that right now and it would be a big job .

woodworks did you put in ventilation from the inner part of the house or between the drylinning?

[GarethM]

It'll be a tanked system, like bubble wrap so the water drips down into a sump.

 

You don't replace the render straight away, as it needs to dry out. Try an exterior wall section as the render is generally just cosmetic.

Edited December 18, 2022 by GarethM

[Woodworks]

1 minute ago, carlos said:

 

woodworks did you put in ventilation from the inner part of the house or between the drylinning?

Inside we have standard trickle vents and mechanical ventilation in bathroom and kitchen as building regs required. Nothing more. If we had our time again would have probably fitted MVHR but not having cold surfaces does stop condensation forming in the first place.

 

We did look at tradition options. Had a heritage builder recommend lime render inside and lime pointing outside. His case was yes the walls get wet but they dry out again when the rain stops. He didn't have an answer when I asked how the walls dry when it rains literally for months on end which it does. When the barn was my workshop water would get right through the 600mm thick windward facing walls and run down the inside. The way we have done it the walls can be soaked but we remain on the dry side. Its a plastic tanking membrane by the way and any water that penetrated runs below the slab and into a sub floor drain. We started from scratch and it would be a bugger of a job as a retrofit in a house you were living in.

[carlos]

cool sounds like a proper job, i could of done something similar in the first place but i didnt , time , funds , lack of knowledge etc, so i will have to make do, the MVHR principle does seem like a good idea and one can get small wall mounted options or multi room loft units. i thought the loft ones may be able to vent through a roof vent which would be easier than going through the stone wall as its 700mm thick and pot luck whether one finds a big stone!

iam going to start with a basic kitchen wall extractor. 

[openspaceman]

45 minutes ago, carlos said:

 the MVHR principle does seem like a good idea and one can get small wall mounted options or multi room loft units.

 

I like the idea of an MVHR  with a built in air to air heat pump, taking warm moist air from the house and venting it well below freezing, circulating the  heat from it back into the house.