Where to place the warming device?

[drowsy swift]

I saw that the ranch had heating devices for sale and autumn is nearing. I asume they are for winter but where exactly do we need to place them?
Do we place them in the barns or coops like in Stardew or do we just place one outside, near the barns and the coops?

[prime rain]

Inside a coop or barn. They heat in the winter and cool in summer, I believe