Hello everyone,
Not necessarily a construction topic, but I hope you experts will still share your expertise and experience 🙂
We are currently looking for a house and have found a very interesting offer: a barn built in 1960, converted into a residential home in 2013 (230m² (2,476 sq ft) living space, 380m² (4,090 sq ft) total usable space, which the energy report is based on). Energy consumption was about 18,000 kWh over the last 3 years, likely due to the well-insulated roof.
What we currently find hard to assess:
The walls are made of (natural) sandstone and are not insulated on the outside (only plastered). About 40cm (16 inches) thick.
Thermally, sandstone is said not to be ideal.
a) Are there any other disadvantages you see that I should be aware of?
b) Is it possible to insulate sandstone walls effectively? What would the approximate cost be for a floor plan of 12 x 12 meters (39 x 39 feet), then 5 meters (16 feet) straight up, plus an additional 7 meters (23 feet) sloping to the roof peak (triangular shape)?
c) For you, is this a deal breaker if someone wants to keep running costs fairly manageable, or could this be a good bargain if the house is otherwise attractive?
Looking forward to your input!
Not necessarily a construction topic, but I hope you experts will still share your expertise and experience 🙂
We are currently looking for a house and have found a very interesting offer: a barn built in 1960, converted into a residential home in 2013 (230m² (2,476 sq ft) living space, 380m² (4,090 sq ft) total usable space, which the energy report is based on). Energy consumption was about 18,000 kWh over the last 3 years, likely due to the well-insulated roof.
What we currently find hard to assess:
The walls are made of (natural) sandstone and are not insulated on the outside (only plastered). About 40cm (16 inches) thick.
Thermally, sandstone is said not to be ideal.
a) Are there any other disadvantages you see that I should be aware of?
b) Is it possible to insulate sandstone walls effectively? What would the approximate cost be for a floor plan of 12 x 12 meters (39 x 39 feet), then 5 meters (16 feet) straight up, plus an additional 7 meters (23 feet) sloping to the roof peak (triangular shape)?
c) For you, is this a deal breaker if someone wants to keep running costs fairly manageable, or could this be a good bargain if the house is otherwise attractive?
Looking forward to your input!
The topic is probably more complex than it seems to you right now.
Until last year, I owned a very old house with some exterior walls made of Baumberger sandstone. However, these walls were significantly older than yours, about 270 years old. They were also usually additionally insulated on the inside with a brick wall built in front of them (if you can call that insulation), making the walls up to about 1 meter (3 feet) thick. 😎
Insulating from the inside is generally not ideal (definitely worse than insulating from the outside). For this reason, I partly installed a ventilated facade on the building, consisting of 10 cm (4 inches) of mineral wool plus larch clapboard siding.
I assume the intended building is in a rural or non-urban area? (Barns usually are.) Different regulations apply there (building permit/planning permission office!), so you should definitely ask beforehand what is allowed. This could mean more restrictions than you might expect. :-8
Until last year, I owned a very old house with some exterior walls made of Baumberger sandstone. However, these walls were significantly older than yours, about 270 years old. They were also usually additionally insulated on the inside with a brick wall built in front of them (if you can call that insulation), making the walls up to about 1 meter (3 feet) thick. 😎
Insulating from the inside is generally not ideal (definitely worse than insulating from the outside). For this reason, I partly installed a ventilated facade on the building, consisting of 10 cm (4 inches) of mineral wool plus larch clapboard siding.
I assume the intended building is in a rural or non-urban area? (Barns usually are.) Different regulations apply there (building permit/planning permission office!), so you should definitely ask beforehand what is allowed. This could mean more restrictions than you might expect. :-8
M
Marvinius20 Dec 2023 21:54xMisterDx schrieb:
Yes, you really should run the numbers because otherwise it doesn’t make any sense. According to a rough rule of thumb, 15,000 kWh per year is generated by a 15 kWp system. However, the problem is that about 75% of that energy is produced when you don’t need it for the heat pump and you end up selling it back to the grid for roughly 8 or 9 cents per kWh. You’ll still only generate around 4,000 kWh of electricity yourself during winter.
On the other hand, besides the heat pump, you have investment costs of easily 15,000 to 20,000 EUR for a 15 kWp system, financed at a current private loan interest rate of 5-6%.
6,000 kWh of heating electricity at 25 cents per kWh costs 1,500 EUR. You can calculate for yourself when you’ll have paid back your photovoltaic investment including interest. It easily takes 15 years.
Get well soon 😉But photovoltaic systems work very well combined with air conditioning for the summer 🙂B
Buchsbaum20 Dec 2023 22:40I don’t want to say anything, but natural sandstone masonry from a building constructed in 1960? Rendered on the outside? Who does that?
I don’t believe you actually have natural sandstone walls. That would be very unusual. And applying rendering or insulation to a natural sandstone façade would be, in my opinion, a major construction mistake.
I suspect you might be confusing something.
I don’t believe you actually have natural sandstone walls. That would be very unusual. And applying rendering or insulation to a natural sandstone façade would be, in my opinion, a major construction mistake.
I suspect you might be confusing something.
Thank you for your feedback so far.
The realtor confirmed again that it is natural sandstone (I explicitly asked if it was natural sandstone or calcium silicate brick). I'm not entirely sure about the plastering anymore—I might be mixing up terms—but the sandstone is visible on only one interior wall; the rest is covered (white on the inside, yellow on the outside).
Understood, so we may have to accept "including additional costs" and hope that these do not triple in the near future.
The realtor confirmed again that it is natural sandstone (I explicitly asked if it was natural sandstone or calcium silicate brick). I'm not entirely sure about the plastering anymore—I might be mixing up terms—but the sandstone is visible on only one interior wall; the rest is covered (white on the inside, yellow on the outside).
Understood, so we may have to accept "including additional costs" and hope that these do not triple in the near future.
B
Buschreiter21 Dec 2023 06:28For your information regarding the costs of an external thermal insulation composite system (ETICS): This year, we paid €140 per m2 (approximately $130 per sq ft) net for a gable wall with one window, including plastering and painting. It could have been significantly more expensive (up to €230 per m2 / about $215 per sq ft)... Additionally, there were scaffolding costs for 6 weeks (€1,300 net) and extending the roof overhang (€5,000 net). Prices are from Cologne!
B
Buchsbaum21 Dec 2023 08:30Newbi23 schrieb:
The real estate agent confirmed again that it is natural sandstone (I specifically asked whether it was natural or calcium silicate brick). Again, I consider it impossible that it is natural sandstone. Please upload a photo. I’m really curious now.
Or is your house from 1860? Then it might be somewhat conceivable.
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