No heat on for 2 weeks

If the temperature stays above freezing, the pipes should be OK, but since you're expecting colder temperatures, I would call someone to stop by and check it.

Can you wrap the pipes with insulation foam, that might help? Found these on Amazon:

https://www.amazon.com/s?k=water+pipe+insulation&ascsubtag=1ba00-01000-a0049-win10-dsk00-smile-us000-pcomp-feature-scomp-wm-5&pldnSite=1&tag=amz-mkt-fox-us-20&ref=aa_scomp

if you are expecting low temperatures your heat should be set on a low temperature to keep your apt pipes from freezing- we were in a condo rental and our next door neighbor left for 2 wks and turned off her heat and hot water and pipes froze and busted and flooded our condo as well because of all the water..you could call your landlord and ask them to check on your apt and the temperature inside

We had an empty home sit for about a year. I just set the thermostat at 50 degrees. It was empty but I didn't want to invite any problems caused by cold and damp weather. The heat will naturally rise.

If you aren't going to be home consider putting timers on your lights.

Also have your mail stopped and same with a news paper so it isn't so obvious nobody is there.

The heat will rise to the apartment above you, but I would be concerned about the water pipes freezing and if that happens the water will obviously affect your apartment. I would contact the landlord and have them go in and check the apartments in your absence.

Not sure if you can winterize part of your home. Here are some tips that might help - https://www.grangeinsurance.com/tips/10-tips-to-winterize-your-home

Hello Henrik. Your apartment upstairs should be ok. Heat rises so that unit should benefit from the 2 heaters you left on and the unit below you. The building being well insulated will also help. But since you expect temps to go below freezing, I'm concerned about freezing pipes. I think you should have someone check on it in your absence. Good luck Henrik.

If this is very concerning to you, perhaps you could alert your landlord and ask them to check your apartment to be sure. In that way you are being a responsible tenant and won't risk damage to the owner's property. They likely have more experience and will appreciate your concern and can hjandle the issue appropriately.

Hi Henrik, I think that you should be okay, heat rises, so the heaters you left on should keep the floor of the apartment warm enough to prevent any freezing in the upstairs apartment.

Here are tipsI for mountain homes. This is what people do to prevent damage when they leave their mountain home.https://www.breckenridgeassociates.com/blog/did-you-know-10-tips-for-winterizing-your-mountain-home.html

I lived in Northern Canada for 20 years, I would have erred on the side of caution and left the heat on in the unused space on 50 degrees F due to the water pipes and possible snow dams on roof. I think you could ask your landlord to at least put in a water alarm in the unheated space to alert someone if the pipe bursts during sub-zero weather. We always used foam liners for pipes in unheated spaces, and also heated pipe covers for problem areas if you have electricity. I don't know about Norway, but if your pipe freezes out to the street, they will turn your water off til Spring thaw so it doesn't affect everyone else's.

Heat does rise I think it will be fine are the heaters safe they won’t start a fire