I'm now wearing a base layer in the morning but I find that on my back, the base layer is too warm. It's the same warmth as the front but with less heat transfer on the back, it feels too warm. Are there any base layer with a cooler fabric on the back side?

Thanks.

Already use wicking treated polyester or wool??

can you sew or find someone who can so add a mesh layer on the hot side,
add air conductive motion under the base layer..

experiment..

I live in a different climate zone than you. so my needs differ..

you chat up your fellow CDN cyclists?

As a fellow CDN cyclist, I think OP is asking too much...I mean winter riding will never be 100% comfortable and there will always be compromises...My advice is to experiment with different base layers and HTFU and put up with a little bit of discomfort. Personally I don't like the idea of clothing with mesh back, imagine if you have to stop or walk for any reason or if the wind is at your back, you will loose a lot of body heat vey fast.

I had a Zzipper bubble fairing so wind went around rather than through the clothing...

My thought was not mesh as the only layer, but maybe a wind block vest under your base layer ,

wind chill from front a problem?

Until Between 15C and 8C, only a base layer under my jersey is enough. I don't need a wind stopper before it gets below 8C.. The thing is I get no cool down on the back so I overheat a bit there, If a two type materials base layer (fleece on front and mesh on back) would exist, I would be fine but I can't find any. May be my only option is like [MENTION=197614]fietsbob[/MENTION] said, build my own.
[MENTION=112025]wolfchild[/MENTION], I could carry a windbreaker for those occasions and even then, jogging beside the bike would prevent me from cooling down too much and if I'm fortunate enough to have strong tail wind (like last Friday), no problem, I'll just go faster and get to work/home sooner

Some russle base layers have the mesh back just search around for mesh back base laywr

My showers pass waterproof/windproof jacket has a vent on the back.

There's a guy who would sew together custom winter gear who used to be talked about all the time here but I'm blanking on his name...

Check out some running or XC ski stuff.

just wait, next week it will be just right

Foxwear. I've got a jacket like that and it's great. I also have a Garneau windvest with a mesh back that I really like, but neither of those are baselayers.

Often the base layer is not the problem, the other layers are.

May help: jacket with mesh back panel, perforated shirt ... or a d-i-y piece you cut holes into.

It's not cold enough for a jacket yet so I simply wear my base layer over my bib and under my jersey and even then, the backside of my base layer is too warm. Front is OK though so the base layer isn't too thick (on the front).