Hello, we recently became homeowners of a two-family house built in 1966, with 17.5 cm (7 inches) calcium silicate brickwork and 150 sqm (1,615 sq ft) of living space.
Currently, the heating is provided by a central oil heating system with small stoves.
The plan is to install a new heating system with radiators (oil condensing boiler) and then insulate the house, including the roof and basement. The windows are already new.
Initially, 14 cm (5.5 inches) insulation with a thermal conductivity of 0.35 W/mK was planned, but due to difficulties related to the roof overhang and other structural conditions, I was advised to use 12 cm (4.7 inches) insulation with 0.32 W/mK instead.
The interior rooms are all covered with drywall panels and behind that, 8 cm (3 inches) of polystyrene insulation (on walls and ceilings). I am not sure if there is a vapor barrier or an air gap behind, but the walls will have to be opened anyway during the heating system work. According to the seller, this was already done during the construction phase.
Now my questions:
Does external insulation still make sense in this case?
If yes, is the proposed insulation adequate?
How much energy savings can be expected from external insulation?
Currently, the heating is provided by a central oil heating system with small stoves.
The plan is to install a new heating system with radiators (oil condensing boiler) and then insulate the house, including the roof and basement. The windows are already new.
Initially, 14 cm (5.5 inches) insulation with a thermal conductivity of 0.35 W/mK was planned, but due to difficulties related to the roof overhang and other structural conditions, I was advised to use 12 cm (4.7 inches) insulation with 0.32 W/mK instead.
The interior rooms are all covered with drywall panels and behind that, 8 cm (3 inches) of polystyrene insulation (on walls and ceilings). I am not sure if there is a vapor barrier or an air gap behind, but the walls will have to be opened anyway during the heating system work. According to the seller, this was already done during the construction phase.
Now my questions:
Does external insulation still make sense in this case?
If yes, is the proposed insulation adequate?
How much energy savings can be expected from external insulation?
Hello,
Whether it still makes sense today to choose oil as an energy source is highly questionable.
Additionally, insulation measures reduce the heating demand. Only once this is known can a heat generator be selected appropriately. Otherwise, frequent cycling is to be expected, which can significantly reduce energy efficiency. It also leads to excessive wear on certain components.
This can be calculated (or arranged to be calculated). Since KFW currently supports individual measures again, professional supervision of the project is advisable anyway.
Best regards
Klweber schrieb:
...The plan is to install a heating system with radiators (oil condensing boiler) and then insulate the house (including the roof and basement, windows are new).
Whether it still makes sense today to choose oil as an energy source is highly questionable.
Additionally, insulation measures reduce the heating demand. Only once this is known can a heat generator be selected appropriately. Otherwise, frequent cycling is to be expected, which can significantly reduce energy efficiency. It also leads to excessive wear on certain components.
Klweber schrieb:
...How much savings can be expected from external insulation?
This can be calculated (or arranged to be calculated). Since KFW currently supports individual measures again, professional supervision of the project is advisable anyway.
Best regards
Klweber schrieb:
The interior spaces are all covered with drywall panels and behind them expanded polystyrene insulation, totaling 8 cm (walls and ceilings) The exterior walls as well?
If so, that is a very unusual method of structural insulation.
Calcium silicate brick has almost no insulating value, and no 17.5 cm (7 inches) brick is really that thin; external insulation is definitely necessary, but only with professional planning!
I’ll refrain from commenting on the oil heating system!
Addendum:
I overlooked that in my haste. Adding exterior insulation will likely cause condensation issues, if they don’t already exist. Check first! Open 1 to 2 m² (11 to 22 sq ft) at a particularly vulnerable spot, for example, the north-facing wall, and determine the current condition.
Best regards.
Klweber schrieb:
...all covered with gypsum board and behind it, Styrofoam insulation totaling 8 cm (walls and ceilings)
I overlooked that in my haste. Adding exterior insulation will likely cause condensation issues, if they don’t already exist. Check first! Open 1 to 2 m² (11 to 22 sq ft) at a particularly vulnerable spot, for example, the north-facing wall, and determine the current condition.
Best regards.
Hello Euro,
unfortunately, the financial aspect has to be considered for a project like this, and switching to an oil condensing boiler was the most cost-effective solution here, especially since new oil tanks have been installed in the basement. Even though the long-term outlook for oil prices is not very positive.
However, I have access to firewood at a reasonable price, which I plan to use as an additional option.
Hello blurboy,
at the moment, the insulation is only on the inside.
The heating system will only be installed once we know if and how the insulation will be done; it will be adjusted accordingly.
The issue with KfW (German development bank) funding is complicated. The initial consultation is at least partly covered, but if the advisory process goes into more detail, it costs us money—and finances are tight.
I am concerned about mold behind the interior insulation; I am even considering using a mold detection dog.
Regards, Klaus
unfortunately, the financial aspect has to be considered for a project like this, and switching to an oil condensing boiler was the most cost-effective solution here, especially since new oil tanks have been installed in the basement. Even though the long-term outlook for oil prices is not very positive.
However, I have access to firewood at a reasonable price, which I plan to use as an additional option.
Hello blurboy,
at the moment, the insulation is only on the inside.
The heating system will only be installed once we know if and how the insulation will be done; it will be adjusted accordingly.
The issue with KfW (German development bank) funding is complicated. The initial consultation is at least partly covered, but if the advisory process goes into more detail, it costs us money—and finances are tight.
I am concerned about mold behind the interior insulation; I am even considering using a mold detection dog.
Regards, Klaus
Oh dear, a building from 1996 and interior insulation—almost every layperson knows this is a no-go.
From my point of view, I recommend removing all the interior insulation on the exterior walls and consulting a professional who can either insulate the house properly from the outside or provide you with expert advice for a DIY approach. Anything else is just madness.
From my point of view, I recommend removing all the interior insulation on the exterior walls and consulting a professional who can either insulate the house properly from the outside or provide you with expert advice for a DIY approach. Anything else is just madness.
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