How to know if a property is eligible

You won't get any of that sort of information as it's private to the current home owner.

The eligibility will depend on age of house, your age, exiting heating systems and such like.

In any event, starting off with what grants are available is the wrong approach

I agree with CH here. Just because there is a grant for a particular upgrade measure and your house qualifies for said grant, this does not necessarily mean that the particular upgrade measure is appropriate or will make a difference to either your comfort or heating bills.

Or in other words: Don't allow the grant tail wag the heat loss dog!

I've been through this.

Stuff that could cause you more problems is:

• Is the roof okay, or need replacing
• Any asbestos anywhere
• What is the waste water system. Is it mains sewerage or do you need to replace a treatment system
• Subsidence/damp/rot/woodworm/structural issues.

I too thought that SEAI grant stuff was important, until I looked at the prices for it. For example, with EWI it might be much less expensive to go the non-grant route. Remember that these grants are for the installers, not the customers. The EWI prices are inflated to cover the costs of the grants. You may be lumbered with the form filling etc, to get the installer's money for them.