There are few rats in the kitchen and they destroy kitchen equipment and food items. They are coming form window louvers at night. Can you please propose a solution except closing the louvers??
Rats are a different problem than mice. Because they are large they present more smell and health issues if they crawl off and die. If exterminating rats it is best to use a rat trap or other device so they die in the open, to be seen and disposed of. Glue traps are inhumane and should be avoided. Poison can be inhumane, but the animal will also crawl away. A rat trap is the most humane method. Methods exist to trap them alive, but few people do that.
You will not successfully keep rats out of the house. When present they must be exterminated. If a nearby building or dwelling takes measures, they will go somewhere else and are a common problem in neighborhoods.
Having a cat works, but a cat is a pet along with all the responsibilities. If you are already considering having a cat as a pet, it would be an option. The best option however is the rat trap.
I've had rats in the house via the kitchen, in the shed and in the garden. In the house they were getting in via a hole in the cavity wall and emerging from under the cooker. Using a tip from a professional exterminator you lay down very fine silica sand (or talcum powder) to see the footprints... then lay your traps accordingly. I tried flour once when I'd run out of talcum powder and they just ate it !!! The pro recommended his bait boxes but I found them to be useless. "Victor" snap traps (baited with anything or nothing) along their routes did the trick in the loft and kitchen and I scored about 7 or 8. Snap traps outside will catch other creatures like hedgehogs. We live in a UK terraced house and they were getting in across the open roof spaces and descending thru the cavity walls into my kitchen. I traced their routes with talcum powder in the loft.
They tend to run along walls/boundaries.
Outside I have lain in wait with an airgun after scattering bait, but they are very hard to kill even with a direct hit. Unless you get them in the head or break a leg, they will just run off (and hopefully die.. maybe). Their skins must be very tough and leathery - I have a pump-action airgun that goes up to maximum permitted energy.
Then I got the "humane" wire-grid rat trap, which catches them alive. Baited with mouldy cheese, bread, stale chocolate cake etc... Place the trap along an edge (of the chicken run, garden etc), and just wait. When you catch one, don't drive into the country and release it. Execute it with the airgun, or drown it. I am up to rat 19 in the garden since late September.
Rat poison in outside bait boxes does work too. I use the "blue grain" type bait. I could use several kilos a year around my chicken coop. The pro's chewy fruit bar bait was ignored inside the bait-boxes in the house.
You feel a lot better fighting back when you can see the results in dead bodies. Burn em bury em or bung em on the compost heap.
You need louvers because you want fresh air. Fortunatelly, air comes through even small holes, and rats don't.
You need to make sure, there are no open holes in your building big enough for rat to come. You could put extra grating behind the louver, or change the louvers to more dense one, so that the rat can't come through (however, you may have problems finding one, so I'd stick to grating).
Another solution is to find out how the rats are getting to the window. If the window start at the ground level, there's nothing that can be done, but if it's higher, maybe they use the branch of the tree or some other item nearby?
They may use holes in the walls, ceiling windows etc., sealing everything may be a big challenge in an old house, especially wooden one, but unless you do that, you can expect much more 'visitors' than rats only.
Treat them with SLS (Sodium Lauryl Sulfate) - controversial toxin available in most commercial liquid soaps, gels and shampoo. It is toxic to bacteria, animals as well as to humans.
First of all clean your louver and its close areas. Then spill a lot of some SLS liquid (the cheapest - the better) where you can (e.g. on outside part of your window), leave it to dry and check the results. They'll hate it.