Gone West

@Pocster I like that, if you don't mind me asking, what's the name of the material?

Thanks for the offer, but I have just looked at the data sheet for ecoCORK and it says shelf-life is 12 months.

I agree, but without cooling the house down in the evenings, it would have just got hotter day by day. We like a warm house and I don't feel comfortable sitting down, unless the temperature is at least 23C.

There was no active cooling and in the summer with long sunny days the inside temperature went up to 26C IIRC. Cooling took place in the evening by opening an outside door and the roof window in the bathroom.

It was a timber I-beam portal frame with 350mm Icynene insulation between the I-beams and 50mm Rockwool outside of the 15mm OSB3 racking, so walls and roof were the same except for the rain screen, U 0.095 W/m2K. Floor was 200mm concrete on 300mm EPS with 200mm upstand, overall U=0.1W/m2K.

As I said, we moved from a Passivhaus, so we were used to very little temperature or humidity variation. It is not that simple though, as we thought the reason it felt uncomfortable was because the temperature, and possibly humidity, changed as you moved closer to the wall, even though the room temperature away from the wall was as expected. After months of heat being pumped into the house the walls warmed up and it felt more comfortable. At the time @SteamyTea explained about the large amount of energy required to remove water from the wall.

There has never been any visual indication that the wall is damp in the three years we have lived here, and as far as we have been able to find out, the wall structure has not changed in the last 50 years. When we moved in, the house had been empty for a year and felt damp. As humidity is generally quite high around here we assumed the structure had just absorbed moisture from the air. Our solution was to heat the building to 23C and ventilate in the summer. It took the best part of a year before we felt the house was ok. We had moved from a Passivhaus where the humidity and temperature was more or less constant all the time, so we may have been more sensitive to the situation here. As I said previously, the wall is hard plastered, which was done in the 1970s. From what has been said it seems that removing the hard plaster and replastering with Hempcrete may be the best solution for increased insulation without greatly affecting 'thermal mass' and the feeling of comfort.

Which is exactly why I started this thread. To find out as much as I can. There is no discernable damp in the wall, which has been the same for the last 50 years. Although I would like to insulate it I don't want to end up with a wall that deteriorates as a result.

So presumably an insulated lime based plaster should be ok, such as hempcrete? Would there be a difference in the effects on the wall, of different types of insulating materials in the plaster, such as hemp or expanded glass beads.

Friends of ours had rain chains. Unfortunately they lived in a windy area and most of the rain was blown off the chains. At least they had large overhangs so the walls didn't suffer.

Many thanks, hempcrete is something I shall be looking into. I have seen it used on buildings featured on TV programmes but I had forgotten about it, old age 😟.

I think it is also linked to age and fitness/health.

Many thanks to all the contributors. This is what makes this forum so useful, a lot of varied information from knowledgeable people. I have decided not to insulate the wall and risk any deterioration. There is no sign of damp or mould, even near the bottom of the wall, so I shall keep it as it has been for the last fifty years even though I shall lose the advantage of having insulation.

I'll think about that. It needs to be big enough that the surrounding area doesn't have an effect.

We get a lot of driving rain but we don't get many freezing nights here. The render is well painted and is at least fifty years old. I am reluctant to alter anything that has worked for fifty years, so covering the inside of the old walls with insulation requires a lot of thought.

I would be very suprised if the old parts of the house have a DPC. The whole house, original 1840s and 'modern' 1970s is cement rendered and there is no visible damp on the inside walls. That's why I was carefully considering whether to cover the inside of the old walls with insulation, in case that takes heat away which is helping to keep the walls dry and therefore the room comfortable.

Presumably a waterproof additive would solve the problem.

So a cement rendered stone wall will keep rain out, as long as it's not got cracks.

The house had been empty for a year before we bought it, and the climate is quite humid down here. My theory was that the fabric of the building, which is a mixture of sandstone and dense concrete block, hard plastered, had absorbed moisture. After we moved in it took a long time for the house to feel comfortable and at the time @SteamyTea explained about the large amount of energy required to dry out an old structure. I am confident that that explanation is correct and now the house is warm and comfortable. It's all covered in layers of old plaster. The house has had a chequered history. Started, around 1840, as a pair of farm workers cottages, stone walls on ground floor and cob upper walls. In the 1970s it was knocked into one and the cob walls removed. Unsound stone walls were replaced with concrete block walls and new roof trusses and concrete tiles added.

No. Now the air temperature has been 23C for a long time the wall surfaces feel warm. We had an old wet door mat out in the unheated boot room and that did smell damp until I dumped it.

Many years ago I had a problem with water running off the road onto my drive. I spoke to Highways about it and they put a 40mm high mound of tarmac along the length of the drive. They said 40mm was the highest they could safely put it.

Thanks, that's really interesting. Food for thought.

Yes, it's the "may/should" bit, I'm not sure about. If the thermal mass is hidden, am I going to end up with an old wall that becomes cold again.

Yes I agree, but what will be more comfortable. We found when we first moved in that it took the best part of a year for the temperature of the fabric of the building to stabilise. @SteamyTea patiently explained about how much energy is required to dry out the old walls. The house felt cold even though the thermometer was reading the right temperature. I'm not sure that covering up the solid wall with a small amount of insulation will help and might make it less comfortable.

Everybody knows what it means though. https://www.greenspec.co.uk/building-design/thermal-mass/ https://www.designingbuildings.co.uk/wiki/Thermal_mass_in_buildings