Hello, I have a plastered stone house built in 1950. It's constructed with approximately 25 cm of lightweight concrete of unknown type + roughly 2 cm of plaster. I've been living here for over 10 years and have done quite a lot of renovation but have been keen on preserving the character of the house.
Therefore, I've previously dismissed the option of additional insulation for building preservation/aesthetic reasons. However, with what I believe will be chronically high electricity prices moving forward, I've started reconsidering additional insulation now that it’s beginning to feel a bit cold in the autumn again. I'm starting to feel somewhat reluctantly that it might not be sustainable in the long term...
In any case, I calculated the existing U-value and used the working figure lambda 0.12 for the lightweight concrete and 0.6 for the plaster, hence having a U-value of approximately 0.44 for the exterior walls. Compared to 0.2 which I understand is the standard today for new construction.
Spontaneously, I think that possible exterior insulation with mineral wool like Rockwool with lambda 0.033 w/m*K could be an option here. If one were to apply 5 cm of rockwool with an overlaying plaster-friendly mesh and plaster system, it would bring the U-value down to ~U 0.26, which I think could feel like a reasonable level of density since it doesn’t affect much aesthetically with window depth eaves, etc., and doesn’t make this old house "too tight". Another positive effect is that you essentially double the heat-storing capacity of the lightweight concrete by applying external insulation.
I haven't found much information about additional insulation of 1950s stone houses. (I know I have some neighbors who have done this on stone house frameworks 10-20 years ago according to the then-current practices with battens/insulation and air gap/wood facade.
Has anyone conducted similar insulation on a stone house facade, or have opinions on the method, insulation materials, or the like? What pitfalls exist?
//Best Regards, Pette
Therefore, I've previously dismissed the option of additional insulation for building preservation/aesthetic reasons. However, with what I believe will be chronically high electricity prices moving forward, I've started reconsidering additional insulation now that it’s beginning to feel a bit cold in the autumn again. I'm starting to feel somewhat reluctantly that it might not be sustainable in the long term...
In any case, I calculated the existing U-value and used the working figure lambda 0.12 for the lightweight concrete and 0.6 for the plaster, hence having a U-value of approximately 0.44 for the exterior walls. Compared to 0.2 which I understand is the standard today for new construction.
Spontaneously, I think that possible exterior insulation with mineral wool like Rockwool with lambda 0.033 w/m*K could be an option here. If one were to apply 5 cm of rockwool with an overlaying plaster-friendly mesh and plaster system, it would bring the U-value down to ~U 0.26, which I think could feel like a reasonable level of density since it doesn’t affect much aesthetically with window depth eaves, etc., and doesn’t make this old house "too tight". Another positive effect is that you essentially double the heat-storing capacity of the lightweight concrete by applying external insulation.
I haven't found much information about additional insulation of 1950s stone houses. (I know I have some neighbors who have done this on stone house frameworks 10-20 years ago according to the then-current practices with battens/insulation and air gap/wood facade.
Has anyone conducted similar insulation on a stone house facade, or have opinions on the method, insulation materials, or the like? What pitfalls exist?
//Best Regards, Pette
What do the windows look like, how much insulation is in the attic, the foundation? Insulating the walls is usually not the most effective way to get warmer and a good investment/lower electricity bill unfortunately.
All windows have been renovated from (2 glass) and now have insulating glass so I guess U~1.8 and of course a bit worse in the frames. But noticed a clear difference when this was addressed.
It is essentially a one-story house with a basement, but we have opened up to the basement.
The basement is drained and in connection with that, we insulated externally with 2 layers (total 20 cm isodrän) along all foundation walls. The basement floor is 2/3 ventilated with a platong floor and exhaust fan on the existing concrete slab which lies directly on a "sand load-bearing layer". On the remaining 1/3, the floor is dug out and the new concrete floor with underfloor heating rests on 20 cm of cell plastic and capillary-breaking macadam.
However, the attic is in its original condition. It has wood shavings and I have considered adding more insulation here, as it is the house's weakest point and also a relatively cheap thing to address. However, I have not done this yet as I understand that I must install a vapor barrier under the wood shavings before I start adding insulation here. This is something that I, of course, need to fix as well.
But otherwise, I feel quite satisfied. We have geothermal heating and I use a lot of supplementary heating and as I said, I do not want to make this house too tight. The ventilation is currently based on natural venting with some exhaust fans.
It is essentially a one-story house with a basement, but we have opened up to the basement.
The basement is drained and in connection with that, we insulated externally with 2 layers (total 20 cm isodrän) along all foundation walls. The basement floor is 2/3 ventilated with a platong floor and exhaust fan on the existing concrete slab which lies directly on a "sand load-bearing layer". On the remaining 1/3, the floor is dug out and the new concrete floor with underfloor heating rests on 20 cm of cell plastic and capillary-breaking macadam.
However, the attic is in its original condition. It has wood shavings and I have considered adding more insulation here, as it is the house's weakest point and also a relatively cheap thing to address. However, I have not done this yet as I understand that I must install a vapor barrier under the wood shavings before I start adding insulation here. This is something that I, of course, need to fix as well.
But otherwise, I feel quite satisfied. We have geothermal heating and I use a lot of supplementary heating and as I said, I do not want to make this house too tight. The ventilation is currently based on natural venting with some exhaust fans.
Is this really true? Are you thinking of ecofiber and sawdust's ability to store moisture in vapor form?Jonatan79 said:
Moist air will want to equalize to the attic when temporary overpressure occurs indoors and then condense if/when the dew point is reached, which it likely will often do in a cold attic. I read a bit on Infoblad.indd (ekofiber.se) about this, and there it states it should be airtight to avoid convection. It is undeniably quite difficult to achieve a hundred percent seal in the attic against, among other things, the outer walls, so I would obviously prefer to avoid it.
Yes, there is a small risk that moisture will find its way up, but if you can access it, it's a good idea to apply a moisture barrier on the attic floor and then add a thicker layer of insulation. What do you mean by sealing the exterior walls? What does the attic look like?
It's an ordinary attic with a gable roof. (Unfortunately too low to furnish. Otherwise, it would probably have been done). There's a chimney in the center where I've laid a few layers of mineral wool boards and a ventilation gap at the eaves every 3rd roof truss or something like that. Otherwise, it's just sawdust insulation 20-25 cm thick, and a board walkway along the ridge... I mostly meant the issue of sealing the edges so to speak, + also all penetrations and even around the chimney, which I'm not sure how to technically approach... It feels like if you don't seal it completely, you might as well ignore it, as I assume you'd get a lot of moisture problems locally at any gaps. But as I said, I need to read up on this a bit better, but I will definitely carry this out one way or another eventually. I got a bit off topic now and as I said, I'm mostly wondering about the building physics on the facade and alternatives on how to smartly do external additional insulation.
Hello
What type of heating do you have? I've also considered the measures you mentioned but concluded that it's difficult to justify. I have a house built in 1951. Former rental property, 260 sqm over two floors with a basement. 30 cm light concrete in the walls and, at best, 40 cm wood shavings in the attic. Original double-glazed windows.
With geothermal heating, I average about 15,000 kWh/year.
It's oceans of time before the energy-saving measures pay off (unless you need to renovate for other reasons).
If you're heating with 1:1 electricity or oil(!) and maybe pellets, the payoff time is obviously shorter and then it's more justifiable.
But I'm following this thread for exciting information.
What type of heating do you have? I've also considered the measures you mentioned but concluded that it's difficult to justify. I have a house built in 1951. Former rental property, 260 sqm over two floors with a basement. 30 cm light concrete in the walls and, at best, 40 cm wood shavings in the attic. Original double-glazed windows.
With geothermal heating, I average about 15,000 kWh/year.
It's oceans of time before the energy-saving measures pay off (unless you need to renovate for other reasons).
If you're heating with 1:1 electricity or oil(!) and maybe pellets, the payoff time is obviously shorter and then it's more justifiable.
But I'm following this thread for exciting information.
Then we have a tiny house in comparison..L lob said:
We have 78 sqm x 2.We drilled and installed geothermal heating as the first thing we did, and that installation has paid for itself many times over, I can say. But we use about 20,000 kWh for 5 people. And I also do some heating with wood. It's still impressive that you manage to keep electricity consumption down to 15,000 kWh on 260 sqm with those walls and windows. I can also recommend contracting out the renovation/insulation of the windows. It costs just a fraction of the price of replacing the windows with everything that entails in a plastered house. For the cost of replacing all windows with triple-pane, you don't get the return overnight, and that's where I feel it becomes overkill. But as I said, we have U-value walls around 3 times new production. If I have the energy, I'll calculate the heat flow that's lost this way...
Considering the phasing out of oil, I'm quite sure that electricity prices will stay at painful levels in the future. However, I plan to do most of it myself and mostly bring in help entirely or partially with the plastering. I don't think it needs to be that expensive. The work steps don't seem that cumbersome considering I'm thinking of a relatively thin additional construction. What I'm considering is the windows where I assume you need to cut away about 5-6 cm on all sides to accommodate insulation in the reveals. Plus, you need to replace all window sills. I don't see the windows ending up a bit deeper as a problem.
I do want to emphasize that this is in the planning stage since I haven't quite anchored this idea at home yet. There's a few other priorities at the moment.
But as I mentioned, not only financially, I'm also bothered by the incredible draft during this time of year. I don't know if you have the same, but it's like the leakage is greatest in the fall when it's slightly above freezing. Or maybe the sensor is acting up. In winter, when it's below freezing, it's more comfortable. Maybe the climate improves when, like in winter, the air is drier?.