Scrum-half John Cooney guided Ulster to a 18-13 victory over Clermont in Pool 3 of the European Champions Cup in testing conditions in Belfast on Friday.
Ireland back-rower Jordi Murphy and Cooney scored either side of the half as the French side found it difficult to settle into the fixture due to the weather and a hostile home following.
"This one is for the purists today with those conditions," uncapped Cooney told BT Sport.
"One of our mantras is fight for every inch, it's something we've worked on for the last few years and you can see it by the way we played for 80 minutes," he added.
Ulster coach Dan McFarland made four changes to the side who beat Bath in England last weekend in their opening match in the competition this season including starting South African winger Louis Ludik.
The visitor's Frank Azema switched half-backs as Scotland's Greig Laidlaw and Australian Jake McIntyre came in for experienced Morgan Parra and Camille Lopez after hammering Harlequins last Saturday.
McFarland's side claimed an early 3-0 advantage as scrum-half Cooney kicked the first of his two penalties.
The hosts dominated the opening half an hour controlling possession in the driving rain and unpredictable wind.
Ireland back-rower Jordi Murphy crossed at the back of a driving maul and Cooney slotted the conversion for a 10-0 lead in front of a raucous Ravenhill crowd.
Azema's men were on the scoreboard after 32 minutes as Laidlaw kicked his first penalty goal of the season but his side trailed 10-3.
Cooney and Laidlaw traded penalties either side of the half and the Irish province led 13-6 with 20 minutes to go.
Conney crossed as he chipped over Raka, took two football-like touches, and slid on the wet surface to score his second try in as many European games after 62 minutes.
Despite his missed conversion the home side led 18-6 and Laidlaw was subbed off for Parra.
The impact of ex-France international Parra was seen immediately as his control behind a dominant Clermont rolling maul led to referee JP Doyle signalling for a penalty try to cut the advantage to 18-13 with 12 minutes to play.
Despite a tense final 10 minutes with Cooney involved in a scuffle with half a dozen Clermont players Ulster held on for their third straight home win over the French outfit.
Azema's men return to the Auvergne region with a losing bonus point but are second in the table two points behind the Irish province.
On Saturday, title holder Saracens welcome the Ospreys in their first home fixture since they were handed a £5 million ($6.5 million) fine and docked 35 points for breaching Premiership Rugby's salary cap rules.