ᐅ How much real savings can be achieved through better wall insulation?
Created on: 9 Dec 2016 10:46
J
Judyyy
Hello everyone,
As some of you already know, I am planning a new build to KfW 55 standards, which I consider a minimum requirement and would ideally like to achieve even better.
We want to build monolithically with Ytong. We also want to have the best possible windows. Regarding floor and roof insulation, I believe that the improvement from KfW 55 to 40 won’t save you much energy. I saw a construction diary online where the builder paid roughly €2,500 (~ $2,700) extra (+ €5,000 (~ $5,400) repayment subsidy) for improved roof and floor insulation but had an already very good timber frame wall. However, prices for Ytong vary quite a lot, so my question is which type of block makes financial sense.
For example, for my house, the costs are approximately:
- 36.5cm (14.4 inches), lambda 0.09, U-value 0.23, about €19,500 (~ $21,000)
- 42.5cm (16.7 inches), lambda 0.09, U-value 0.20, about €22,700 (~ $24,500)
- 42.5cm (16.7 inches), lambda 0.08, U-value 0.18, about €26,800 (~ $28,900)
- 48.0cm (18.9 inches), lambda 0.08, U-value 0.16, about €30,300 (~ $32,700)
- 48.0cm (18.9 inches), lambda 0.07, U-value 0.14, about €42,400 (~ $45,700)
These prices are from price lists found online.
I think the last block with a U-value of 0.14 and an extra cost of roughly €12,000 (~ $13,000) can be ruled out immediately.
I have two questions:
1. If we stick to KfW 55, up to which block thickness or quality does the extra cost make financial sense?
I’m generously assuming a timeframe of 30 years, which should be the period to pay off the house. The goal is to finish within 25 years.
2. Is it possible to reach KfW 40 standards with the block that has a U-value of 0.16?
A brief overview of the house:
- 180 m² (1,938 sq ft) living and usable space
- Probably a ground source heat pump with trench collectors
- Probably photovoltaics
- Probably controlled mechanical ventilation with heat recovery
- At least KfW 55 standard
I hope you can help me with this.
Best regards,
Judyyy
As some of you already know, I am planning a new build to KfW 55 standards, which I consider a minimum requirement and would ideally like to achieve even better.
We want to build monolithically with Ytong. We also want to have the best possible windows. Regarding floor and roof insulation, I believe that the improvement from KfW 55 to 40 won’t save you much energy. I saw a construction diary online where the builder paid roughly €2,500 (~ $2,700) extra (+ €5,000 (~ $5,400) repayment subsidy) for improved roof and floor insulation but had an already very good timber frame wall. However, prices for Ytong vary quite a lot, so my question is which type of block makes financial sense.
For example, for my house, the costs are approximately:
- 36.5cm (14.4 inches), lambda 0.09, U-value 0.23, about €19,500 (~ $21,000)
- 42.5cm (16.7 inches), lambda 0.09, U-value 0.20, about €22,700 (~ $24,500)
- 42.5cm (16.7 inches), lambda 0.08, U-value 0.18, about €26,800 (~ $28,900)
- 48.0cm (18.9 inches), lambda 0.08, U-value 0.16, about €30,300 (~ $32,700)
- 48.0cm (18.9 inches), lambda 0.07, U-value 0.14, about €42,400 (~ $45,700)
These prices are from price lists found online.
I think the last block with a U-value of 0.14 and an extra cost of roughly €12,000 (~ $13,000) can be ruled out immediately.
I have two questions:
1. If we stick to KfW 55, up to which block thickness or quality does the extra cost make financial sense?
I’m generously assuming a timeframe of 30 years, which should be the period to pay off the house. The goal is to finish within 25 years.
2. Is it possible to reach KfW 40 standards with the block that has a U-value of 0.16?
A brief overview of the house:
- 180 m² (1,938 sq ft) living and usable space
- Probably a ground source heat pump with trench collectors
- Probably photovoltaics
- Probably controlled mechanical ventilation with heat recovery
- At least KfW 55 standard
I hope you can help me with this.
Best regards,
Judyyy
As a rough estimate, in my opinion, you can calculate it this way. Inflation and interest charges on the investment are simply left out, which is good enough for a rough idea.
The heating costs of €800 are probably even overestimated with a brine heat pump and horizontal ground collector, which makes the calculation look even worse...
Improving the walls will never pay off. The living comfort doesn’t really increase either... -> do it for your ecological conscience or don’t bother 😉
The heating costs of €800 are probably even overestimated with a brine heat pump and horizontal ground collector, which makes the calculation look even worse...
Improving the walls will never pay off. The living comfort doesn’t really increase either... -> do it for your ecological conscience or don’t bother 😉
Tego12 schrieb:
Improving the walls will never pay offAt least not unless energy prices change significantly. But that’s just guessing or pure speculation.
I wouldn’t count on it.
My ecological conscience would of course love to implement it, but not my financial gut feeling 😀
Phew, I really need to sleep on this once more 😕
I am also planning a photovoltaic system at the same time, preferably as large as possible 😀
And combined with a heat pump and aiming for the highest possible self-consumption, a better wall probably becomes even less economical 🙁
Phew, I really need to sleep on this once more 😕
I am also planning a photovoltaic system at the same time, preferably as large as possible 😀
And combined with a heat pump and aiming for the highest possible self-consumption, a better wall probably becomes even less economical 🙁
T
toxicmolotof11 Dec 2016 04:46A photovoltaic system, even if as large as possible, is not cost-effective either when combined with a ground-source heat pump or when aiming for a high self-consumption rate.
With some luck, you might break even after 10-15 years. However, by that time, the lifespan of the modules and/or inverter will likely be nearing its end.
Even with a storage system, this scenario is unlikely to happen.
This mostly serves the ecological idea—if you completely disregard the impacts of manufacturing and disposal. ;-)
With some luck, you might break even after 10-15 years. However, by that time, the lifespan of the modules and/or inverter will likely be nearing its end.
Even with a storage system, this scenario is unlikely to happen.
This mostly serves the ecological idea—if you completely disregard the impacts of manufacturing and disposal. ;-)
P
Peanuts7412 Dec 2016 11:03toxicmolotow schrieb:
A photovoltaic system, no matter how large, is not cost-effective when considering both the ground-source heat pump and a high level of self-consumption.
With some luck, you might break even after 10-15 years. However, by then the lifespan of the modules and/or inverters will likely be nearing its end.
And with battery storage, even this scenario won’t happen.
This only serves the ecological (nice typo) idea if you completely ignore manufacturing and disposal. ;-)The modules should last longer, but the inverters would already be quite old at 15 years, something like Juppi Heesters territory. The whole eco-insulation craze will hardly pay off in most cases. And even my own green conscience wouldn’t be at peace if you look at the rest of the world. In the US, wooden houses have single-pane glazing and are so drafty you can stick your finger between the frame and sliding window.
In winter, heating is just cranked up at full blast. Conversely, refrigerators are generally large but so poorly insulated that they run 80-90% of the time. Cars are sometimes modified to produce as much smoke as possible; otherwise it’s mostly pickups (gasoline V8 engines) that rarely get below 20 liters per 100 km (about 12 mpg).
On pickup beds you almost never see anything lying around. Africa, China, India, and others—all environmental regulations are a joke or simply don’t exist.
And the German government thinks it can save the planet by sticking 20 cm (8 inches) or more of polystyrene on houses???
Just for info, I also try to save electricity, gasoline, etc., and I care a lot about the environment, but the focus should be on completely different issues.
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