I would like to set up a small system with the following components:

• moisture sensor(s)
• temperature sensor(s)
• relay switching of mains power up to 110V / 1200W

The power relay is what gives me the problem.
Any suggestions ?

The applications at my house are multiple:

1. Control of attic fans. The off-the shelf controller on the attic fans just turn them on when the attic temperature is over 80 degrees F, but I want to not turn them on unless the attic is hotter than the outside. So I want a 10-foot cable to a sensor that can be under the eaves.
2. My wife's palm propagation greenhouse.

• thermostat control of heating mats under the germination flats
• thermostat control of fans, again need to ensure that the outside is cooler than the greenhouse before turning it on
• warning when plants are getting dry

But a 60W power limit is too little. Is there a good, safe mains power relay that I can drive with a contact closure in the Onion's relay module?

I doubt that I am the only one with these needs.