For the record (and thanks for the PM). The question above was about takeoff lengths at ISA+15 degC?
The answer from EMB airport planning manual is:
1,860m for ISA+15 at sea level SL at MTOW (20,000kgs; no t/r);
1,390m for ISA+15, SL, and TOW for a 400nm sector (16800kgs TOW, no t/r).
So the +15 degC adds 60-100m, for this aircraft and these assumptions.
Of interest - the ICAO method for estimating runway length for non-standard conditions (aerodrome design manual; part 1 runways; 1984; 2nd ed) proved to be (of necessity) conservative, and would have given 2024m for ISA+15 at sea level SL at MTOW (20,000kgs; no t/r).