ᐅ Is it necessary to heat the attic during winter?

Hello everyone! 🙂

I usually just read along quietly and have learned a lot from this forum, especially in the financing section. Thank you very much for that!

At the beginning of this year, I bought my parents’ house (a mid-terrace house, built in 1999).

The attic has been converted into living space (there are 2 radiators installed; it used to be my childhood bedroom). Unfortunately, we don’t know what kind of insulation was used since we no longer have any documents about it, and my mother doesn’t remember either.

The attic has two Velux roof windows, which are also from 1999.

You reach the attic via a folding staircase and a regular interior door. So, I don’t think there is much insulation between the attic and the rest of the living space (everything is quite open anyway).

The attic is currently completely unused and is not (yet) used for storage, since we have a basement.

Now I’m wondering: do I have to heat the attic during winter? And if yes, to what temperature? I’m a bit worried about mold...

There is no mechanical ventilation system, so I have to ventilate manually (is once a week enough?).

Thanks in advance for your answers! 🙂

Best regards!

You don’t have to. Just make sure to ventilate regularly.
However, the door to the floor might warp due to a large temperature difference, and too much cold air could come down from above, keeping the room at around 12–15°C (54–59°F).

It depends on where the insulation is located. Is the roof open with the ceiling insulated, or is the roof itself insulated?

Hello everyone,

thank you very much for your replies!

Regarding the insulation: I can’t say for sure right now... I would have to ask my mother if she still remembers.

What would be the difference? Does one require heating and the other not?

Thanks in advance and best regards!

If the attic is within the insulated building envelope (which I assume if it is used as living space and radiators are installed), it should not be left unheated.
When warm, moist indoor air passes through open doors or door gaps into the attic, the air cools down. As a result, it can no longer hold as much moisture, causing condensation to form.
This is exactly when mold develops.
The warped door mentioned by Nordlys is likely a consequence of water condensing on or inside the cold door.

It is certainly possible to calculate the temperature required to avoid condensation using the dew point. However, I am not the right person to do that.