You have a couple options. The easy route is to do what was already suggested and just bump up your strike temp a little. But, if you're not scared of a little math, you can do the following.
Follow the link and determine what your heat loss is and convert it to an equivalent volume of water. The website will explain this in more detail. http://www.haandbryg.dk/mashcalc.html
At this point, you can use the infusion equation instead of the strike equation to determine your strike temp. To do this, solve for Aw (the actual temperature of the infusion water).
Say you go the website and determine your heat loss to be equivalent to 0.46 quarts of water. Lets say your grain temp is 70F and you have 12 lbs of it. You want to mash in with 12 quarts of water and hit 154F. The math goes as follows.
Aw = [(T2-T1)(.2G + Wm) / Vi] + T2 Where T1 = Grain temp F, T2 = Target mash temp F, G = Total amount of grain in pounds, Wm = The equivalent volume of water that you determine, and Vi = Infusion volume (or in this case strike water volume)
Aw = [(154-70)(.2*12 + 0.46) / 12] +154
Aw = 174 So, your stike temp is 174F with heat loss accounted for.