Sublease space rose again in June, though it is still a smaller percentage of total office availability than it was at the beginning of the year.

Greenway Plaza was the main driver of the leap: Occidental Petroleum put about 814K SF on the sublease market between 5 Greenway Plaza and 3 Greenway Plaza, and Sheridan Production Co. listed 71K SF at 9 Greenway Plaza, bringing the Houston sublease office market to 9.3M SF of availabilities.

That pushed the NAI Partners Sublease Index, which measures the amount of sublease space as a percentage of total available space, up 100 basis points to 15.3% in June.

Dynegy's merger with Vistra also beefed up sublease availability, putting about 102K SF on the market at 601 Travis Downtown. All three companies — Occidental, Sheridan and Dynegy — are tied to energy, continuing the trend of most of Houston's sublease woes coming from that sector.

Class-A office still has the lion's share of sublease space, with 7.8M SF listed for sublease, almost 21% of total Class-A availability.