  We present new thermal IR photometry and spectral energy distributions (SEDs)
of eight classical Cepheids (type I) and three type II Cepheids, using VISIR
thermal IR photometric measurements, supplemented with literature data. We used
the BURST mode of the instrument to get diffraction-limited images at 8.59,
11.25 and 11.85 {\mu}m. The SEDs show a IR excess at wavelengths longer than
10{\mu}m in ten of the eleven stars. We tentatively attribute these excesses to
circumstellar emission created by mass loss from the Cepheids. With some
hypotheses for the dust composition, we estimated a total mass of the envelope
ranging from 10-10 to 10-8 M\odot. We also detect a spatially extended emission
around AX Cir, X Sgr, W Sgr, Y Oph and U Car while we do not resolve the
circumstellar envelope (CSE) for the other stars. The averaged circumstellar
envelope brightnesses relative to the stellar photosphere are {\alpha}(AX Cir)
= 13.8\pm2.5%, {\alpha}(X Sgr) = 7.9\pm1.4%, {\alpha}(W Sgr) = 3.8\pm0.6%,
{\alpha}(Y Oph) = 15.1\pm1.4% and {\alpha}(U Car) = 16.3\pm1.4% at 8.59 {\mu}m.
With this study, we extend the number of classical Cepheids with detected CSEs
from 9 to 14, confirming that at least a large fraction of all Cepheids are
experiencing significant mass loss. The presence of these CSEs may also impact
the future use of Cepheids as standard candles at near and thermal infrared
wavelengths.
