UPDATE 1-Spain's ACS H1 EBITDA up 6.6 pct on energy

* H1 EBITDA 790 mln euros, up 6.6 pct

* Net 501 mln euros, down 67 pct on lower one-off gains

* Energy and industrial services fuel core earnings growth

* Shares up 0.7 pct, outperforming sector and Madrid index

(Adds detail, shares)

MADRID, July 29 (Reuters) - Spanish builder ACS (ACS.MC) said core earnings rose 6.6 percent in the first half thanks to growth at its energy and industrial services division.

Growth in international industrial services and domestic renewable energy offset a decline in business at ACS's construction division, which depends on a weak Spanish real estate market.

Earnings before interest, tax, depreciation and amortisation (EBITDA) rose to 790 million euros ($1.03 billion) from 741 million a year earlier.

Net profit fell 67 percent to 501 million euros, though the year-earlier period was inflated by one-off gains from the sale of ACS's 35 percent stake in power group Union Fenosa to Gas Natural (GAS.MC).

ACS said it had extended its equity swap derivative contract with Natixis bank on 4.88 percent of Iberdrola (IBE.MC) by one year to 2012.

ACS shares were up 0.7 percent at 33.295 euros at 0750 GMT, outperforming the STOXX Europe 600 construction and materials index .SXOP. (Reporting by Jonathan Gleave; editing by Will Waterman) ($1=.7684 Euro)