I am using S05 to make a porter/stout (let's not have that discussion), one of the things is that the ambiant temperature in my house is quite high (28 degrees celcius), I can cool it down for a few days while fermenting to 20-25 using (expensive) airconditioning. I was just wondering when is it safe to increase the temperature back to 28 degrees without creating too many esters?
Given that Fermentis lists the maximum fermentation temperature for US-05 as 18-28°C, you should be fine as long as the fermenting beer doesn't go too far outside of that range. During the first ca. 2-3 days, the yeast metabolism is quite exothermic but how much this affects the temperature of the fermenting wort depends on many factors, not the least of which is fermenter size. From my personal experince with US-05 in 12l and in 32l fermenters, I would estimate about +5°C in the first 2-3 days. A neat trick that I have seen with a few homebrewers in warmer climates is to wrap the fermenters in light blankets (or old tshirts) and use evaporative cooling by periodically wetting the fabric. Alternatively, the entire fermenter can be put in a water bath with the blanket being in constant contact with the water so that capillary force keeps the blanket moist at all times. With the aid of a fan blowing on the wet fabric, the heat of fermentation should easily be cancelled out.
There's many ways to keep cool I think all of them have been discussed here.
As far as your question. Once you're past the growth phase especially and high krausen to be safe a little more heat generally isn't to bad.
One trick is to do a very large yeast pitch to basically skip most of the growth phase where most esters are generated. This can be done with a multi-step starter or pitching the entire trub from a compatible batch. When doing this the yeast go right to feeding and warmer temps is less of a concern.