Can I use both de minimus safe harbor for HO improvement and the square foot safe harbor in the same year?

You can only elect one, and the election for any tax year is irrevocable. No depreciation is allowed for the years in which the safe harbor is elected.

Selecting a Method

• You may choose to use either the simplified method or the regular method for any taxable year.
• You choose a method by using that method on your timely filed, original federal income tax return for the taxable year.
• Once you have chosen a method for a taxable year, you cannot later change to the other method for that same year.
• If you use the simplified method for one year and use the regular method for any subsequent year, you must calculate the depreciation deduction for the subsequent year using the appropriate optional depreciation table. This is true regardless of whether you used an optional depreciation table for the first year the property was used in business.

Full details on the new option can be found in Revenue Procedure 2013-13 

Thanks.  I'll use the sq ft method. 

I wasn't thinking about the de minimus only being for improvements, and that would still require the 39.5yrs of depreciation and resulting recapture of same when/if I sell my house in the future, which would lower it's benefit.  The amount of eventual recapture is definitely something to take into account.