Just bought a house, time to make it frugal!

Background: 24y/o, just bought a house, loves traveling and expensive hobbies. Doesn't mind being frugal to be able to afford previously mentioned things.

The house is one floor with a basement, each 63m² (680sqft). There's an insulated double door garage that is 46m² (495sqft). It's a wooden house, built in 1948, in northern Scandinavia. Basement has concrete walls and floor. Windows are all triple-glass windows that are only a couple of years old. New roof a couple of years ago as well. The house is heated by district heating, so hot water running into radiators. There's also floor heating in the hallway and kitchen. The garage has an air heat pump and floor heating although I don't see the need for floor heating there.

Heating

Now it is summer time and even though I live quite far north we do get warm weather here as well. What I have done so far is to turn down all the radiators to cold and I'm trying to figure out how to turn off the floor heating. The air heat pump in the garage is off and the floor heating is off as well. In the winter I will run the air heat pump at its lowest setting just to de-ice my car and give it healthier startups (it's a diesel car).

Lighting

One of the first things I did when I moved in was to go through every single lamp in the house and make sure it was LED. I found a couple of old 40 and 60 watt lamps and also some old energy-saving lamps that I also replaced. Replacing the old energy-saving lamps didn't make much sense money-wise but they are so slow to light up that I didn't mind spending a little extra money on new lamps. Ikea ryet lamps are so cheap anyways. In total I made a saving of around 250 watts.

Appliances

The fridge/freezer in the kitchen is not super new and probably not super efficient. I will get a new one but not for energy efficiency but for size. So I will probably reduce my electricity bill by a little there. I have also gone around the house to try to find things that are plugged in and on stand-by. I got a lot of stuff with the house when I bought it, several stereos (pretty much one in each room) and many other things. I bought an electricity meter for this so I can figure out how much power they draw in stand-by. I did some testing yesterday and found that my TV + living room stereo draws around 60-65 watts in stand-by. I had a spare remote controlled power outlet so I put everything on that. If I can turn that off when I'm not using it (say around 18hrs/day) I can save around 410kWh/year. I don't know exactly how much my electricity costs yet but that's probably enough money saved to pay for a trip to and from the airport once a year. I also have a fridge/freezer in the basement that I don't really need (especially not when I get a new fridge/freezer for the kitchen). It is still plugged in now because the freezer needs de-icing and I haven't gotten to it yet. I plugged it to the electricity meter last night and in 10 hours it has used ~0.8kWh. If that's the average it means it uses around 700kWh/year and that's a lot of money for something that I don't actually need. Next step is to check how much my computer+monitor uses in stand-by. I could turn them off probably 13hrs/day and put the switch right next to the computer to make it convenient (or just use a remote controlled outlet like I did for the stereo and tv).

Insulation The house seems to be pretty well insulated already but I will still make some improvements to it. The attic is not insulated so it keeps the same temperature as the outside. The attic floor has sawdust insulation right now. Not sure how thick it is though. My plan is to add a layer of rockwool insulation all over the attic floor. That should help stop heat from escaping from the house into the attic and stop cold in the attic to creep down into the house. Next year I will tear off all the wooden panel on the outside of the house, add a layer of insulation, and put on new wooden panel. I need to replace the panel anyways so while I'm at it I might as well add a layer of insulation.

Are there any other things I should think of when trying to keep the costs down?