Hello
We are currently considering selling our house built in 2000 and building a new one.
You often hear that the house should be insulated as well as possible, and so on. But what insulation is actually good, and what is a reasonable compromise in terms of cost and benefit? We have quite clear ideas about how the house should look, yet every builder comes up with different suggestions. Only Poroton blocks are agreed on by all.
Here are the basic details:
3-gable house
12 x 9.5 meter (31 ft x 31 ft) beam structure with a 1 meter (3 ft) overhang on one third of the garden side, so then 10.5 meters (34 ft)
1 meter (3 ft) knee wall
Mechanical ventilation with heat recovery
Underfloor heating in all rooms
Minimum KfW 70 standard achieved through insulation, not technology
Builder 1 offers 24 cm (9.5 inches) walls + 16 cm (6 inches) external thermal insulation composite system (ETICS) with 0.40 W/m²K roof insulation 20 cm (8 inches) 0.35 W/m²K
Builder 2 offers 17.5 cm (7 inches) walls + 16 cm (6 inches) ETICS and 20 cm (8 inches) roof insulation 0.35 W/m²K
Builder 3 suddenly wants to achieve this with 17.5 cm (7 inches) walls and only 10 cm (4 inches) ETICS.
We currently favor builder 1, even though they are significantly more expensive (about 15,000 euros). I would like to know if the insulation they offer is really good or rather below standard, so some improvements would be necessary. I would appreciate advice to clarify this.
Olli
We are currently considering selling our house built in 2000 and building a new one.
You often hear that the house should be insulated as well as possible, and so on. But what insulation is actually good, and what is a reasonable compromise in terms of cost and benefit? We have quite clear ideas about how the house should look, yet every builder comes up with different suggestions. Only Poroton blocks are agreed on by all.
Here are the basic details:
3-gable house
12 x 9.5 meter (31 ft x 31 ft) beam structure with a 1 meter (3 ft) overhang on one third of the garden side, so then 10.5 meters (34 ft)
1 meter (3 ft) knee wall
Mechanical ventilation with heat recovery
Underfloor heating in all rooms
Minimum KfW 70 standard achieved through insulation, not technology
Builder 1 offers 24 cm (9.5 inches) walls + 16 cm (6 inches) external thermal insulation composite system (ETICS) with 0.40 W/m²K roof insulation 20 cm (8 inches) 0.35 W/m²K
Builder 2 offers 17.5 cm (7 inches) walls + 16 cm (6 inches) ETICS and 20 cm (8 inches) roof insulation 0.35 W/m²K
Builder 3 suddenly wants to achieve this with 17.5 cm (7 inches) walls and only 10 cm (4 inches) ETICS.
We currently favor builder 1, even though they are significantly more expensive (about 15,000 euros). I would like to know if the insulation they offer is really good or rather below standard, so some improvements would be necessary. I would appreciate advice to clarify this.
Olli
First of all, thank you for your replies.
I will try to clarify my statements a bit.
Now, that was vaguely expressed. I was referring to the companies we have spoken to so far. And they all build with "Poroton."
Okay. How thick would it need to be approximately?
Alright, then let's agree on "dormer gable." The provider calls it a "Frisian house," but the name isn’t really important for us.
The location is southeastern Lower Saxony, in the triangle between Hanover, Braunschweig, and Hildesheim.
The house itself will be built in the old village center, so not on the edge of fields or similar.
The house is roughly oriented with the dormer gable (I’m learning) to the southwest, and without shading.
By “I don’t care for now,” I mean I am open to all suggestions.
Basically, the standard offered is hollow brick + ETICS. I have doubts whether it makes sense to suddenly have the construction companies (all three build the shell structures with their own employees) use other materials. What good is the best insulated block if it is processed incorrectly afterward?
If there are reasons speaking against ETICS, I’m open to hearing them.
My basic idea is a gas condensing boiler plus controlled mechanical ventilation with heat recovery to manage the ventilation "problem" and for comfort (several acquaintances highly recommend it). I actually do not want solar thermal systems at all.
KfW 70 may also be misleading on my part. The funding is not important to me. I want to build a house that offers a good compromise between construction costs and running costs. In other words, I don’t want a “perfect” house on paper that, for example, is calculated with a heat pump or pellet stove but actually causes high heating costs.
I want to find out up to which point it makes sense to insulate more, and from where the effort becomes disproportionately high compared to the benefit. Unfortunately, I don’t know how to describe it better.
Our preferred specifications are listed as follows in the construction description:
Windows: triple-glazed with a U-value of 0.6
Ground slab: 110 mm (4.3 inches) at WLG 035
Walls: 24 cm (9.5 inches) Poroton + 16 cm (6 inches) ETICS
Roof: 20 cm (8 inches) mineral wool at WLG 035
So the question is where it makes sense to improve without, for example, investing 15,000 euros to save 50 euros in gas later.
Regards,
Olli
I will try to clarify my statements a bit.
Quote from zerogt: ↑
Only Poroton is used by everyone.
Hardly. There are quite a few who build with aerated concrete, expanded clay, calcium silicate bricks, pumice, or concrete.
Now, that was vaguely expressed. I was referring to the companies we have spoken to so far. And they all build with "Poroton."
Quote from zerogt: ↑
Minimum KfW 70 by insulation, not technology.
In my opinion, the thickness of the roof insulation doesn’t fit with any of the three providers...
Okay. How thick would it need to be approximately?
Quote from zerogt: ↑
3-gable house
12 x 9.5 timber frame on 1/3 of the garden side, projecting 1 m out, so then 10.5
For a classic 3-gable house, the third gable is quite small... Our comparable houses all have a depth of 3.00 m (10 feet) in the third gable. What you describe I would rather call a dormer.
Alright, then let's agree on "dormer gable." The provider calls it a "Frisian house," but the name isn’t really important for us.
Currently, 16 cm (6 inches) External Thermal Insulation Composite System (ETICS) would be considered “normal.” If you choose a house with ETICS, depending on the location and site conditions, both 17.5 cm (7 inches) or 24 cm (9.5 inches) external masonry could work.
The location is southeastern Lower Saxony, in the triangle between Hanover, Braunschweig, and Hildesheim.
The house itself will be built in the old village center, so not on the edge of fields or similar.
The house is roughly oriented with the dormer gable (I’m learning) to the southwest, and without shading.
These days, there is a lot of talk about insulation, less about how specific KfW requirements can be met; this is not only achievable through additional insulation. Much of it remains “on paper” only; in my opinion, for example, heat recovery in ventilation systems. For me, this means you first have to decide what you want. Do you want to build a single-family house with ETICS or maybe a monolithic house, as described by the “Doc” or “Manu?” A statement like “I don’t care how the heat is retained in the building envelope” is, in my opinion, not very helpful. Houses built with ETICS are usually less expensive... although I don’t always understand that; actually, it should be the other way around.
By “I don’t care for now,” I mean I am open to all suggestions.
Basically, the standard offered is hollow brick + ETICS. I have doubts whether it makes sense to suddenly have the construction companies (all three build the shell structures with their own employees) use other materials. What good is the best insulated block if it is processed incorrectly afterward?
If there are reasons speaking against ETICS, I’m open to hearing them.
You also write that you don’t want to heat with electricity – what exactly do you mean by that? Do you want a classic gas condensing boiler with solar heating support? Because “I don’t care what KfW says” can only apply if you waive KfW funding; then only the currently valid energy saving regulations need to be followed.
My basic idea is a gas condensing boiler plus controlled mechanical ventilation with heat recovery to manage the ventilation "problem" and for comfort (several acquaintances highly recommend it). I actually do not want solar thermal systems at all.
KfW 70 may also be misleading on my part. The funding is not important to me. I want to build a house that offers a good compromise between construction costs and running costs. In other words, I don’t want a “perfect” house on paper that, for example, is calculated with a heat pump or pellet stove but actually causes high heating costs.
I want to find out up to which point it makes sense to insulate more, and from where the effort becomes disproportionately high compared to the benefit. Unfortunately, I don’t know how to describe it better.
Our preferred specifications are listed as follows in the construction description:
Windows: triple-glazed with a U-value of 0.6
Ground slab: 110 mm (4.3 inches) at WLG 035
Walls: 24 cm (9.5 inches) Poroton + 16 cm (6 inches) ETICS
Roof: 20 cm (8 inches) mineral wool at WLG 035
So the question is where it makes sense to improve without, for example, investing 15,000 euros to save 50 euros in gas later.
Regards,
Olli
B
Bauexperte15 Oct 2014 12:08Hello Olli,
You want to use a gas condensing boiler, so I think 240 mm (9.5 inches) will probably be required. However, you will only know for sure once the online form 153 is completed or, if KfW funds are not relevant, when the energy certificate is calculated.
The wind blows across the land there without any obstacles 😀
I would definitely advise against that. By the way, it is quite normal these days that most general contractors build the shell with their own teams. External trades usually only come in starting from the carpenter’s work.
Me—get into trouble again? No thanks…
Today, from an economic perspective, a KfW 70 efficiency house is reasonable; anything beyond that is more a question of conviction or hobby, as I see it.
Like most suppliers, your contractor has succumbed to competitive games. They state the Ug value of the glazing, not the much more important overall U-value of the entire window unit. As a client, I would also want to know which profiles are used (5-chamber or more) and safety features like mushroom-head locks.
By the way, the floor slab specification only reflects the required values from the reference building. Our floor slabs show a U-value of 0.26 W/(m²K) but are also significantly thicker. It would be interesting to know the construction of the ceiling above the ground floor in this context. If you opt for a walk-in shower, do you have a visible “experience” from the room below?
Reading your data above, I think you’ll only know exactly after the house is calculated. As I said before—and this is just my subjective impression—the values for the floor slab and installed insulation don’t look very impressive to me...
Best regards, Bauexperte
zerogt schrieb:
Ok. How thick would/should it approximately be?
You want to use a gas condensing boiler, so I think 240 mm (9.5 inches) will probably be required. However, you will only know for sure once the online form 153 is completed or, if KfW funds are not relevant, when the energy certificate is calculated.
zerogt schrieb:
Location is southeastern Lower Saxony in the triangle between Hannover, Braunschweig, and Hildesheim.
The wind blows across the land there without any obstacles 😀
zerogt schrieb:
I have my doubts whether it’s wise to suddenly have the construction companies (all three build the shell with their own employees) work with different materials. What good is the best insulated brick if it’s installed incorrectly afterward?
I would definitely advise against that. By the way, it is quite normal these days that most general contractors build the shell with their own teams. External trades usually only come in starting from the carpenter’s work.
zerogt schrieb:
If there are reasons against using ETICS (external thermal insulation composite system), I’m happy to hear them.
Me—get into trouble again? No thanks…
zerogt schrieb:
I just want to find out up to which point it makes sense to add more insulation and when the effort becomes disproportionately high compared to the benefit. Unfortunately, I don’t know how to explain it better.
Today, from an economic perspective, a KfW 70 efficiency house is reasonable; anything beyond that is more a question of conviction or hobby, as I see it.
zerogt schrieb:
Our preferred specifications are, for example, as follows in the build performance description:
Triple-glazed windows with a Ug value of 0.6 mentioned
110 mm (4.3 inches) floor slab insulation WLG 035
Walls: 24 cm (9.4 inches) Poroton + 16 cm (6.3 inches) ETICS
Roof: 20 cm (7.9 inches) mineral wool WLG 035
Like most suppliers, your contractor has succumbed to competitive games. They state the Ug value of the glazing, not the much more important overall U-value of the entire window unit. As a client, I would also want to know which profiles are used (5-chamber or more) and safety features like mushroom-head locks.
By the way, the floor slab specification only reflects the required values from the reference building. Our floor slabs show a U-value of 0.26 W/(m²K) but are also significantly thicker. It would be interesting to know the construction of the ceiling above the ground floor in this context. If you opt for a walk-in shower, do you have a visible “experience” from the room below?
zerogt schrieb:
So the question is where it still makes sense to improve without, for example, investing 15,000 euros and then only saving 50 euros in gas.
Reading your data above, I think you’ll only know exactly after the house is calculated. As I said before—and this is just my subjective impression—the values for the floor slab and installed insulation don’t look very impressive to me...
Best regards, Bauexperte
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