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
D
Doc.Schnaggls10 Oct 2014 15:21Hello Olli,
my favorite for solid masonry construction would be a monolithic build—meaning a 36.5 cm (14.4 inches) Poroton brick WITHOUT external thermal insulation (ETICS / EIFS)...
Is that not an option for you?
Best regards,
Dirk
my favorite for solid masonry construction would be a monolithic build—meaning a 36.5 cm (14.4 inches) Poroton brick WITHOUT external thermal insulation (ETICS / EIFS)...
Is that not an option for you?
Best regards,
Dirk
And we are building KfW 70 WITHOUT insulation. Specifically, with 36cm (14 inches) T9 Poroton bricks. The only technology we have is a ground-source heat pump – no ventilation system, no solar thermal, no photovoltaic panels. This way, the thicker masonry also protects against heat in the summer. ;-)
How the heat is retained within the building envelope is not my main concern, so a monolithic construction could also be an option. What matters to us is a minimal energy demand without the additional costs for insulation—whether that means thicker masonry or more external thermal insulation—becoming uneconomical. Another absolute no-go is heating with electricity. Geothermal energy on the property is difficult: for surface or trench collectors, space is quite limited, and I would prefer to avoid borehole systems due to former mining activities (not even considering the permitting). What is the current standard for roof insulation, and what is considered better than standard? I don’t really care what the KfW says; what’s important is a genuinely low energy demand, not just figures made to look better through formulas because wood happens to be in vogue or because certain technologies are currently promoted.
B
Bauexperte13 Oct 2014 11:10Hello Olli,
These days, there is a lot of talk about insulation and less about how specific KfW requirements can be met; this is not only achievable by extra insulation. Much of it happens “only on paper,” in my view, for example the heat recovery in ventilation systems. For me, this means you first need to decide what you want. Do you want to build a single-family house with ETICS or maybe a monolithic house, as "Doc" or "Manu" described? 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 more affordable… although that is not always clear to me; actually, it should be the other way around.
You also write that you don’t want to heat with electricity—what exactly do you mean by that? Do you want classic heating with a gas condensing boiler and solar heating support? Because "regardless of what KfW says," that can only apply if you forgo KfW funding; then only the currently valid energy saving regulations have to be met.
Regards, Bauexperte
zerogt schrieb:That’s normal. Even if you go to a kitchen showroom, each salesperson will offer you something different 😉
We have quite fixed ideas about how the house should look, yet every builder comes with different proposals.
zerogt schrieb:Hardly. Many builders use aerated concrete, expanded clay, sand-lime brick, pumice, or concrete as well.
Only Poroton is wanted by all.
zerogt schrieb:For a classic 3-gable house, the third gable is rather small… our comparable houses all show a depth of 3.00 m (10 feet) in the third gable. What you describe I would rather call a cross gable.
3 gable house
12x9.5 beam on one third of the garden side, protruding 1 m (3 feet 3 inches), so then 10.5
zerogt schrieb:In my opinion, the thickness of the roof insulation does not meet the requirement with any of the three providers...
Minimum KfW 70 through insulation, not technology.
zerogt schrieb:Currently, 16 cm (6 inches) of external thermal insulation composite system (ETICS) would be considered standard. If you decide on a house with ETICS, depending on location and site conditions, this can work well both with 17.5 cm (7 inches) external masonry or 24 cm (9.5 inches) block.
We currently favor provider 1 even though they are significantly more expensive (+-15,000 euros). I would just like to know if the insulation is really good or rather below standard; if so, it would need to be improved.
These days, there is a lot of talk about insulation and less about how specific KfW requirements can be met; this is not only achievable by extra insulation. Much of it happens “only on paper,” in my view, for example the heat recovery in ventilation systems. For me, this means you first need to decide what you want. Do you want to build a single-family house with ETICS or maybe a monolithic house, as "Doc" or "Manu" described? 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 more affordable… although that is not always clear to me; actually, it should be the other way around.
You also write that you don’t want to heat with electricity—what exactly do you mean by that? Do you want classic heating with a gas condensing boiler and solar heating support? Because "regardless of what KfW says," that can only apply if you forgo KfW funding; then only the currently valid energy saving regulations have to be met.
Regards, Bauexperte
D
DerBjoern13 Oct 2014 12:10zerogt schrieb:
Minimum KfW 70 based on insulation, not on technical equipment
Provider 1 offers 24cm (9.4 inches) walls + 16cm (6.3 inches) external thermal insulation composite system (ETICS) with a U-value of 0.40, roof 20cm (7.9 inches) with 0.35
Provider 2 offers 17.5cm (6.9 inches) walls + 16cm (6.3 inches) ETICS and 20cm (7.9 inches) roof with 0.35
Provider 3 suddenly wants to achieve this with 17.5cm (6.9 inches) walls and only 10cm (3.9 inches) ETICS.Providers 1 and 2 don’t sound too bad so far. Regarding the roof insulation, I agree with the building expert. It’s not bad, but also not very generous. What kind of ETICS does Provider 1 plan to use with a U-value of 0.4? Common EPS foam has 0.35 and is actually quite affordable.
Manu1976 schrieb:
And we are building KFW 70 WITHOUT insulation. Using 36cm (14.2 inches) T9 Poroton bricks. The only technical equipment we have is an air-to-water heat pump—no ventilation, no solar thermal, no photovoltaics. This way the thicker masonry also protects against heat in summer. ;-)Walls with 36cm (14.2 inches) T9 bricks aren’t exactly great either. That results in a U-value of about 2.35. That’s rather at the lower end nowadays.
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