External insulation — 10 cm vs 8 cm. Will it make a big difference in energy use?
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Hi,
We are renovating an old house in NW Italy. It is partially built by stone/brick mix and partially only brick. We will be putting an external insulation. We have recently got quotes on 10 cm and 8 cm cork insulation. For the whole house the difference in price to put 8 cm will be 1300 Euros less. We are wondering if the price difference is worth our efforts? Is there a huge difference in energy capabilities of the two? we will have underfloor radiant heating, hooked up to a system power by gas and also solar water heating. any toughts for us? would you need more information then what is provided already?
The specks are as follows:
10 cm cork Technical Characteristics :
-Nominal Density : 108/120 kg/mc
– Heat conductivity: 0.0375 W/m K
– Heat resistance: 2,6667 m²K/W
– Sollecitazione alla compressione: ≥ 134 kPa ± 8 kPa
– Water absorbance: Wit < 0,36% ± 0,12% – Fire resistance: Euroclasse E – Dimensions: cm 100×50 – Thickness: mm 100 8 Cm technical characteristics: Nominal Density : 108/120 kg/mc Heat conductivity: 0.0375 W/m K Heat resistance: 2,1333 m²K/W – Sollecitazione alla compressione: ≥ 127 kPa ± 8 kPa Water absorbance: Wit < 0,38% ± 0,12% Fire resistance class: Euroclasse E Dimension: cm 100×50 Thickness: mm 80
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Replies
Canan,
Cork insulation has an R-value of about R-3.1 per inch. So 8 cm (or 3.15 inches) of cork insulation has an R-value of R-9.8, while 10 cm (3.94 inches) of cork insulation has an R-value of R-12.2. It should come as no surprise that the insulating value of the 10-cm. product is 25% higher than the insulating value of the 8-cm. product.
Neither R-value is very high. But what are heating costs like in Italy? I have no idea. If you're paying only $100 a year for heat, maybe it doesn't matter. If you're paying $2,000 a year for heat, it clearly matters.
Certainly these insulation levels — R-10 or R-12 — would be considered laughably low anywhere in the U.S. Here in Vermont, I would suggest using at least three times as much insulation. But if you live in sunny Italy, and you're having breakfast on the patio in February, it may not matter.
Hi Martin,
thanks for this. We are neither in Vermont nor in Florida :-) somewhere in between with coldish winters (some snow included) for about 3 months and hotter summers. 10 cm is the legal limit needed for certification if we want to get a tax benefit for the retrofitting process, fingers crossed they may have some science behind that number but you never know, as they keep changing the legal limits (we think to avoid paying for the renovation jobs).
we will have 16 cm (8 cm cork and 8 cm wood fiber) in the roof, and good windows as well. hopefully these will all help with our heating costs.
thanks again for your comments