Hi, first post here.
I am working on refurbishment (I hesitate to call it a renovation) of our 1930's house. I hope this sufficiently 'period' for this forum as I've found browsing useful and interesting in the past. It has cavity walls (about 50mm) and mostly suspended timber ground floors. So not necessarily a building requiring fully traditional techniques/materials to function, but I would like to try and be sensitive to how it was originally intended to work whilst making some modern improvements, mainly to improve efficiency. The first major job was extracting blown fibre cavity wall insulation that had dropped into most of the subfloor ventilation pathways and made the void very humid, full of condensation, bridged the cavity and DPC in various places etc. Thankfully only very limited signs of rot or infestation and now the airflow is restored it should dry out sufficiently. One thing that I have noticed is a lot of the airbricks do not have a direct path to a corresponding opening in the inner skin. Some seem to be intended only to ventilate the cavity, but there are also openings on the inner skin that are offset from where the airbricks are so the airflow would be along the cavity and then into the void. There are also airbricks below the eaves, some of which again have corresponding interior openings so are presumably for room ventilation, but several do not. Obviously for these ones they could have been covered on the inside and plastered/decorated over so I could just be unable to see the internal openings.
So, questions: Is this a typical setup for subfloor ventilation in a house this age - i.e. some internal openings offset from airbricks? And also how important it is for the cavity to be directly ventilated in this way? My understanding is that as long as any water that penetrates the outer skin can run down without being bridged to the inner skin, the cavity will be functioning as needed. Perhaps builders of earlier cavity walls like this were overzealous in the amount of ventilation the cavity itself would require? In the interest of warming the place up (it is rather cold with the wind whistling through the cavity walls now!), I am contemplating installing bead insulation to the cavities (after some time has passed for drying), which are supposed to allow water to move down the cavity without bridging it to the inner skin and are non absorbent so won't retain water in the cavity either. Obviously this would also stop any meaningful airflow through the cavity from the exterior leaf only airbricks. Is this a terrible idea? If I went ahead with it I would need to make sure there were enough airbricks with direct paths to the subfloor void, therefore I could install periscopic vents that would retain subfloor ventilation with the rest of the cavity filled. I'd likely need to make extra openings to the void on the inner skin for this to work - would I need to fill in the old ones for the sake of wall strength?
Thanks for any insights!
I am working on refurbishment (I hesitate to call it a renovation) of our 1930's house. I hope this sufficiently 'period' for this forum as I've found browsing useful and interesting in the past. It has cavity walls (about 50mm) and mostly suspended timber ground floors. So not necessarily a building requiring fully traditional techniques/materials to function, but I would like to try and be sensitive to how it was originally intended to work whilst making some modern improvements, mainly to improve efficiency. The first major job was extracting blown fibre cavity wall insulation that had dropped into most of the subfloor ventilation pathways and made the void very humid, full of condensation, bridged the cavity and DPC in various places etc. Thankfully only very limited signs of rot or infestation and now the airflow is restored it should dry out sufficiently. One thing that I have noticed is a lot of the airbricks do not have a direct path to a corresponding opening in the inner skin. Some seem to be intended only to ventilate the cavity, but there are also openings on the inner skin that are offset from where the airbricks are so the airflow would be along the cavity and then into the void. There are also airbricks below the eaves, some of which again have corresponding interior openings so are presumably for room ventilation, but several do not. Obviously for these ones they could have been covered on the inside and plastered/decorated over so I could just be unable to see the internal openings.
So, questions: Is this a typical setup for subfloor ventilation in a house this age - i.e. some internal openings offset from airbricks? And also how important it is for the cavity to be directly ventilated in this way? My understanding is that as long as any water that penetrates the outer skin can run down without being bridged to the inner skin, the cavity will be functioning as needed. Perhaps builders of earlier cavity walls like this were overzealous in the amount of ventilation the cavity itself would require? In the interest of warming the place up (it is rather cold with the wind whistling through the cavity walls now!), I am contemplating installing bead insulation to the cavities (after some time has passed for drying), which are supposed to allow water to move down the cavity without bridging it to the inner skin and are non absorbent so won't retain water in the cavity either. Obviously this would also stop any meaningful airflow through the cavity from the exterior leaf only airbricks. Is this a terrible idea? If I went ahead with it I would need to make sure there were enough airbricks with direct paths to the subfloor void, therefore I could install periscopic vents that would retain subfloor ventilation with the rest of the cavity filled. I'd likely need to make extra openings to the void on the inner skin for this to work - would I need to fill in the old ones for the sake of wall strength?
Thanks for any insights!