Stock index futures briefly trimmed gains on Tuesday after construction starts on homes fell unexpectedly in March, but a drop in borrowing costs for Spain helped eased concerns about the European debt crisis.

S&P 500 futures rose 7.9 points and were above fair value, a formula that evaluates pricing by taking into account interest rates, dividends and time to expiration of the contract. Dow Jones industrial average futures added 62 points and Nasdaq 100 futures rose 10.5 points.

(Reporting By Edward Krudy; Editing by Padraic Cassidy)