Are you secured only by the home owned free and clear? In that case, it would be a home equity loan for TRID.
Are you additionally secured by the investment home being purchased? In that case, it would be a home purchase loan for TRID.
TRID purpose is always tied to your collateral. If you have multiple pieces of collateral, then it is tied to any of the pieces. In other words, you start down the waterfall: purchase--if loan is to purchase any of the properties securing your loan, then it's a purchase for TRID. Refinance, construction, home equity...same thing.
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I'm fixin' to fix that.