ᐅ Snow melts faster from the roof compared to neighboring houses.

I noticed that the snow on my roof melts much faster than on my neighbors’ roofs. This surprises me because I have a low-energy house with an insulated ceiling and a double-ventilated cold roof. The neighbors have “standard” houses with knee walls and insulated roofs. Does anyone have an idea why my roof seems to lose more heat? I’m worried there might be insufficient insulation.

Your insulation quality will be worse in that case, which is unusual for a low-energy house. Has a blower door test been conducted? Have you already discussed this with the construction company?

Hello Krambambulli,

The reason the snow melts off the roof is due to the roof warming up, which is clear, but especially with a ventilated roof, I wonder how that can happen.
The insulation can be good and thick, but the airtightness of roofs is always a critical factor. With a leaky vapor barrier, warm air can penetrate into the insulated cavity—and possibly into the ventilation layer of your roof as well.
However, without seeing the situation on site and, above all, without knowing the design details, it is impossible to say more.
As my predecessor mentioned: Was there an airtightness test done on the roof, and what were the results?

Finally, a few words about “low-energy houses”: A building does not become a low-energy house solely through thermal insulation calculations, as many adjustments and factors can be used to improve the numbers. You also have to consider and optimize all building components. Therefore, it is possible that the roof insulation in your house is thinner than that of your neighbors.

So, if the snow melts faster on your roof than on the neighboring one, the thermal insulation is likely inadequate. Of course, it also depends on the roof pitch; are they the same? And how the houses are positioned relative to the sun—these conditions should be roughly similar as well.

If these factors are about the same, then check the thermal insulation: were the required insulation layers actually installed? I have seen cases where only 40 insulation mats were installed, but 150 were billed. The customer often cannot verify this afterwards, since everything is sealed.

This is how I see it, and too much heat is lost here. I suspect the wrong insulation was used. This construction mistake is quite significant. 🙁

In this situation, I would also be surprised that the snow on my roof is melting faster than at the neighbor’s. Simply check the insulation here, which is not so easy either. But find out the cause.