I've got a couple of reasons:
1. He is doing it for the game. He knows very well that couples are more in threat of evictions (he's seen the past seasons and he took notes well). So if he started to have a relationship with her in the house, he will more likely to be evicted soon. He knows that all too well.
2. He just doesn't find her too attractive perhaps and that she isn't his type? From a gay point of view, I think that she's perfectly stunning. If I were straight and she was digging me, she'd be my wife in a second - totally my type of girl (even Nathan said he'd go straight for her). Maybe Ed really is into brunettes as he says he is - perhaps women resembling Rachel McAdams, Mila Kunis, Natalie Portman...
3. Jade has a weird resemblance to his sister. Seriously, Ed's sister (seen on eviction show) looked more like she could related to Jade than Ed. Maybe he sees Jade as being too similar-looking looking to his sister? From what I hear people wouldn't go for those resembling a family member.
4. He's probably gay? Yeah, yeah, an immature one. But it happens -- Lots of 'hard' men like him go far in life, having wife and kids, and never come out because of the stigma (a masculine rough guy is sleeping with men - ohhh loooorrrddd!). What they'd do is, go out to gay bars, sleep with a man and come back home to their wife. It's sad.