Hello everyone,
I have built an extension using 40mm (1.6 inch) sandwich panels. These were screwed onto a wooden framework made of 10×10cm (4×4 inch) timber and 12×6cm (5×2.4 inch) rafters. Since this room should not freeze in winter and will occasionally be heated properly, I am now considering whether it makes sense to add insulation between the rafters. The choice of insulation material is still unclear. I would make the thickness correspond to the size of the beams (10 or 12cm / 4 or 4.7 inches). On the inside, I would like to cover it with 15mm (0.6 inch) OSB panels since I already have these available.
Now I am not sure if this will work without causing condensation problems or similar issues. What other construction layers would be good and safe? Or is it a bad idea to add more insulation to the sandwich panels?
I entered the construction details into Ubakus, but I can’t really interpret the results properly.
Attached is also a picture of the construction from the inside.
I appreciate any advice.
Have a nice evening
I have built an extension using 40mm (1.6 inch) sandwich panels. These were screwed onto a wooden framework made of 10×10cm (4×4 inch) timber and 12×6cm (5×2.4 inch) rafters. Since this room should not freeze in winter and will occasionally be heated properly, I am now considering whether it makes sense to add insulation between the rafters. The choice of insulation material is still unclear. I would make the thickness correspond to the size of the beams (10 or 12cm / 4 or 4.7 inches). On the inside, I would like to cover it with 15mm (0.6 inch) OSB panels since I already have these available.
Now I am not sure if this will work without causing condensation problems or similar issues. What other construction layers would be good and safe? Or is it a bad idea to add more insulation to the sandwich panels?
I entered the construction details into Ubakus, but I can’t really interpret the results properly.
Attached is also a picture of the construction from the inside.
I appreciate any advice.
Have a nice evening
Hi,
A 40mm sandwich panel usually means the exterior is quite airtight, whether by design or construction; either way, moisture can no longer escape. If you then add another 10–12cm (4–5 inches) of insulation on the inside and close it off with 15mm (0.6 inches) OSB, you are potentially creating a second vapor barrier that may not function properly with occasional heating. Maintaining a consistently warm or consistently cold environment is simpler; this “heating from time to time” is a classic cause of condensation from a building physics perspective. OSB can work, but only if airtightness is taken very seriously—every single screw counts. The choice of insulation material also matters; using vapor-permeable insulation helps somewhat but won’t magically solve the problem. Your hygrothermal simulation software probably shows some critical values that people tend to dismiss, but ignoring them here would not be a good idea.
A 40mm sandwich panel usually means the exterior is quite airtight, whether by design or construction; either way, moisture can no longer escape. If you then add another 10–12cm (4–5 inches) of insulation on the inside and close it off with 15mm (0.6 inches) OSB, you are potentially creating a second vapor barrier that may not function properly with occasional heating. Maintaining a consistently warm or consistently cold environment is simpler; this “heating from time to time” is a classic cause of condensation from a building physics perspective. OSB can work, but only if airtightness is taken very seriously—every single screw counts. The choice of insulation material also matters; using vapor-permeable insulation helps somewhat but won’t magically solve the problem. Your hygrothermal simulation software probably shows some critical values that people tend to dismiss, but ignoring them here would not be a good idea.
Thank you for your response, nauer.
What would be your suggestion to improve the insulation?
With ubakus, I only see a red bar at the bottom and just a few “drops”… but since I’m not familiar with it, I don’t really know how to interpret this correctly…
Would it help to drill holes in the OSB or leave “openings” so the moisture can escape?
The temperature always needs to stay above 0 degrees Celsius (32°F) and might sometimes be heated up to 15 degrees Celsius (59°F)…
Best regards, fabi
What would be your suggestion to improve the insulation?
With ubakus, I only see a red bar at the bottom and just a few “drops”… but since I’m not familiar with it, I don’t really know how to interpret this correctly…
Would it help to drill holes in the OSB or leave “openings” so the moisture can escape?
The temperature always needs to stay above 0 degrees Celsius (32°F) and might sometimes be heated up to 15 degrees Celsius (59°F)…
Best regards, fabi
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