HELOC used to build another home

unfortunately, that transaction is not tax deductible in any year,

please see publication 936 and half way down the middle column of page 2 it states:

"Note. Interest on home equity loans and lines of credit are deductible only if the borrowed funds are used to buy, build, or substantially improve the taxpayer’s home that secures the loan"

https://www.irs.gov/pub/irs-pdf/p936.pdf 

since you didn't use the money to buy, build or substantially  improve YOUR home, it's not tax deductible. (it still wouldn't be tax deductible if you used the money to build a 2nd home for yourself because it has to be used on the home that "secured the loan")