6.    Property and Equipment, Net

Property and equipment, net, consisted of:

 

		December 31, 2013												December 31, 2012
(in $ millions)		Cost				Accumulated depreciation				Net				Cost				Accumulated depreciation				Net
Capitalized software			650				(449	)			201				629				(386	)			243
Computer equipment			281				(139	)			142				274				(138	)			136
Building and leasehold improvements			17				(8	)			9				12				(7	)			5
Construction in progress			76				—				76				32				—				32
			1,024				(596	)			428				947				(531	)			416

As of December 31, 2013 and 2012, the Company had net capital lease assets of $104 million and $94 million, respectively, included within computer equipment. During the years ended December 31, 2013 and 2012, the Company invested $139 million and $155 million, respectively, in property and equipment, including capital lease additions. Additions in the year ended December 31, 2013 include upgrades to equipment as part of investment in the Company’s GDS information technology infrastructure.

The Company recorded depreciation expense of $126 million, $145 million and $139 million during the years ended December 31, 2013, 2012 and 2011, respectively.

The amount of interest on capital projects capitalized was $6 million and $3 million for the years ended December 31, 2013 and 2012, respectively.