We made a down payment to a home builder less than a month ago. Due to unforeseen
Circumstances, we decided not to have the house built. Nothing has been started
Yet. Can we still get a full or partial refund from the builder?

That depends on your contract with the builder. You need to read the contract and see if there is any cancellation clause.

If not, you can try negotiating with the builder.

Possibly. Was your contract conditioned on anything, such as you obtaining financing? Will the unforeseen circumstances prevent you from obtaining financing? If so then you should be able to get a full refund of your deposit.

The best thing to do is contact the builder immediately and explain the situation. If the builder is not willing to work with you then you need to sit down, carefully read your contract and possibly speak to an attorney about your options.

Speak to an attorney ASAP! The money you spend on an atty could save your EMD(earnest money deposit) or down payment. Good luck to you.