I found that using a powder which was poisonous to ants worked for me - put a line of it along any door sills, and maybe windows as well if you think they could get in there. If you can find their nests, bung a load of the powder down there, and it will kill them. You should be able to find this in a store selling agricultural stuff. There might be sprays as well - I haven't seen any. If the places where the ants get in will get rainfall on them, then these products might not work when you are away from the house (they would get washed off).
The best thing is to make sure that there is nothing to attract the ants, they search for the smallest crumbs of food. Also make sure that any climbing plants on your house are pruned away from the windows - ants often climb these, especially if there is any greenfly on them - and get in that way.
I found that using a powder which was poisonous to ants worked for me - put a line of it along any door sills, and maybe windows as well if you think they could get in there. If you can find their nests, bung a load of the powder down there, and it will kill them. You should be able to find this in a store selling agricultural stuff. There might be sprays as well - I haven't seen any. If the places where the ants get in will get rainfall on them, then these products might not work when you are away from the house (they would get washed off).
The best thing is to make sure that there is nothing to attract the ants, they search for the smallest crumbs of food. Also make sure that any climbing plants on your house are pruned away from the windows - ants often climb these, especially if there is any greenfly on them - and get in that way.