ᐅ Is it worth investing in insulation beyond the standard requirements for new construction?
Created on: 8 Jul 2015 19:25
G
Grym
Concepts like these from the prefab house provider Kampa initially sound quite good, and there are many people in forums who believe that nowadays you shouldn’t build a house with a U-value above 0.15.
On the other hand, when you calculate the raw numbers, I struggle to understand how insulation beyond what is necessary can actually be cost-effective.
Let’s take a 140-150 sqm (1500-1600 sq ft) house with 1.5 stories as an example. This would have an exterior wall surface area of about 170 sqm (1830 sq ft) (excluding roof, top floor ceiling, foundation slab, and windows, with a relatively high knee wall as we plan).
The local provider, in a standard case, offers a U-value of 0.21, while Kampa advertises 0.11. According to a U-value calculator, the local provider’s wall consumes 16 kWh/m² per year, and the 0.11 U-value leads to 7 kWh/m² per year. Calculated over the surface area, that’s 2,720 kWh versus 1,190 kWh. With an air-to-water heat pump with an annual performance factor of 4.1 (yes, these are available for about 4,000 EUR – greetings to the purple forum), this equates to 663 kWh_el versus 290 kWh_el. So, you save about 373 kWh just from the exterior wall construction. Variant A: standard solid construction and Variant B: passive house wall. In strict monetary terms, that’s about 93.25 EUR per year or 7.77 EUR monthly installments.
Over 20 years, the difference adds up to 1,865 EUR. In 20 years!!!
Of course, additional savings come from insulating the foundation slab, roof, and better windows in a passive house, but those also require separate higher investments.
On the other hand, a photovoltaic self-consumption system can save a lot, especially during transitional seasons (self-generated electricity costs less than half compared to grid electricity). This is particularly true for an energy-saving standard house, which benefits significantly from PV power during these periods, unlike a KFW40-level house where heating is mostly needed only in the coldest winter months.
The question in the end is: is it even worth it, or is the current energy-saving regulation standard already so strict that the economic feasibility has long been exceeded?
There’s also a bit of a question between timber frame prefab houses versus solid construction. Only with a timber frame prefab house can you achieve a high insulation value for the exterior facade with a reasonably manageable wall thickness (in cm). In my opinion, this is the only advantage of a timber frame prefab house compared to solid construction.
On the other hand, when you calculate the raw numbers, I struggle to understand how insulation beyond what is necessary can actually be cost-effective.
Let’s take a 140-150 sqm (1500-1600 sq ft) house with 1.5 stories as an example. This would have an exterior wall surface area of about 170 sqm (1830 sq ft) (excluding roof, top floor ceiling, foundation slab, and windows, with a relatively high knee wall as we plan).
The local provider, in a standard case, offers a U-value of 0.21, while Kampa advertises 0.11. According to a U-value calculator, the local provider’s wall consumes 16 kWh/m² per year, and the 0.11 U-value leads to 7 kWh/m² per year. Calculated over the surface area, that’s 2,720 kWh versus 1,190 kWh. With an air-to-water heat pump with an annual performance factor of 4.1 (yes, these are available for about 4,000 EUR – greetings to the purple forum), this equates to 663 kWh_el versus 290 kWh_el. So, you save about 373 kWh just from the exterior wall construction. Variant A: standard solid construction and Variant B: passive house wall. In strict monetary terms, that’s about 93.25 EUR per year or 7.77 EUR monthly installments.
Over 20 years, the difference adds up to 1,865 EUR. In 20 years!!!
Of course, additional savings come from insulating the foundation slab, roof, and better windows in a passive house, but those also require separate higher investments.
On the other hand, a photovoltaic self-consumption system can save a lot, especially during transitional seasons (self-generated electricity costs less than half compared to grid electricity). This is particularly true for an energy-saving standard house, which benefits significantly from PV power during these periods, unlike a KFW40-level house where heating is mostly needed only in the coldest winter months.
The question in the end is: is it even worth it, or is the current energy-saving regulation standard already so strict that the economic feasibility has long been exceeded?
There’s also a bit of a question between timber frame prefab houses versus solid construction. Only with a timber frame prefab house can you achieve a high insulation value for the exterior facade with a reasonably manageable wall thickness (in cm). In my opinion, this is the only advantage of a timber frame prefab house compared to solid construction.
For a gas condensing boiler or a heat pump, I would estimate a lifespan of anywhere between 10 and 25 years. Around 10 years if things go badly, and over 20 years is really a stroke of luck. These are technical/mechanical devices, similar to cars, so they wear out. You can already see this from the fact that boilers older than 30 years have to be replaced – was there any big outcry? No, because very few boilers actually last that long.
Windows can, in the worst case, become “blind” after only 10 years, as far as I know that is the term used. For colored windows where the color is applied by film, eventually the color peels off; I know a recent case like this. To my knowledge, the house is just over 10 years old, and the window colors have turned into a messy combination of white and the applied (?) window color. However, I don’t know if this applies to all colored windows.
Exterior plaster should be professionally cleaned after 10 to at the latest 15 years (possibly with a new coat including fungicides). The service life of external thermal insulation composite systems (ETICS or EIFS) today is stated as 30 years. It can be as much as 40 years, but also only 20 years.
These points are actually arguments in favor of timber prefabricated houses – after 40 years, you could strip the interior, “thermally recycle” the timber frame, and then build a new house on the hopefully valuable plot of land (in a reasonably good location, after 40 years the main value is in the land anyway, regardless of whether it’s solid construction or prefabricated). Maybe a bungalow?
Windows can, in the worst case, become “blind” after only 10 years, as far as I know that is the term used. For colored windows where the color is applied by film, eventually the color peels off; I know a recent case like this. To my knowledge, the house is just over 10 years old, and the window colors have turned into a messy combination of white and the applied (?) window color. However, I don’t know if this applies to all colored windows.
Exterior plaster should be professionally cleaned after 10 to at the latest 15 years (possibly with a new coat including fungicides). The service life of external thermal insulation composite systems (ETICS or EIFS) today is stated as 30 years. It can be as much as 40 years, but also only 20 years.
These points are actually arguments in favor of timber prefabricated houses – after 40 years, you could strip the interior, “thermally recycle” the timber frame, and then build a new house on the hopefully valuable plot of land (in a reasonably good location, after 40 years the main value is in the land anyway, regardless of whether it’s solid construction or prefabricated). Maybe a bungalow?
S
Sebastian799 Jul 2015 20:59Yes, with a timber frame house you can build a nice fireplace and then a solid house.
Anything is possible – but after 10 years, windows won’t stay clear. You can also choose brick cladding, then you won’t have any worries about the exterior.
Anything is possible – but after 10 years, windows won’t stay clear. You can also choose brick cladding, then you won’t have any worries about the exterior.
By the way, blind windows can be renovated without replacing the glass: just try searching for glass restoration.
My parents have standard uPVC double-glazed windows that are now over 35 years old, and none of the panes have become blind yet (however, the Velux roof windows have already been replaced because of this). It’s always a matter of the quality you bought. The insulation values are probably significantly better today, but they also have to match the masonry. Since renovating a brick facade is neither easy nor inexpensive, it’s simply a calculation whether it makes sense to do it. While this doesn’t necessarily increase the value of the house, it doesn’t really matter if you’re not planning to sell.
With today’s new build standards, you should still be in a good position even after many years, so I wouldn’t worry too much. The important thing is that the entire insulation concept is coordinated. In my opinion, it doesn’t help to have well-insulated walls if the windows are poorly insulated, and vice versa.
My parents have standard uPVC double-glazed windows that are now over 35 years old, and none of the panes have become blind yet (however, the Velux roof windows have already been replaced because of this). It’s always a matter of the quality you bought. The insulation values are probably significantly better today, but they also have to match the masonry. Since renovating a brick facade is neither easy nor inexpensive, it’s simply a calculation whether it makes sense to do it. While this doesn’t necessarily increase the value of the house, it doesn’t really matter if you’re not planning to sell.
With today’s new build standards, you should still be in a good position even after many years, so I wouldn’t worry too much. The important thing is that the entire insulation concept is coordinated. In my opinion, it doesn’t help to have well-insulated walls if the windows are poorly insulated, and vice versa.
S
Sebastian7910 Jul 2015 08:58Yes, you could drop dead tomorrow – that’s always a possibility. And I don’t need to google to find negative experiences from people – do you really think someone would write, "Hey everyone, my windows have lasted 25 years already – strong, right?"?
That’s naive thinking... You are very focused on numbers, which comes across in many posts – but you have a very limited perspective.
That’s naive thinking... You are very focused on numbers, which comes across in many posts – but you have a very limited perspective.
I never said that the windows need to be replaced after 10-15 years. I only mentioned that their best years are behind them—kind of like an 8-9 year old Audi A6. It’s no longer new, but you can still use it for another 5-6 years. Windows that are 15 years old can easily be used for another 10 years. However, the “shine” is gone, and the best years are behind them. The same applies to the heating boiler and other components in a 15-year-old house.
You should always save for something to maintain the value of the house...
You should always save for something to maintain the value of the house...
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