From the Ilford data sheet http://www.ilfordphoto.com/products/product.asp?n=12#
"Hoya R72 and Kodak Wratten 89B. These
filters give an even more dramatic effect than deep red
filters. However, exposure times with these filters can be
very long, so the use of a tripod is recommended."
If you look at the spectral response curve for this film you will see that the infra-red sensitivity peaks at 720 nm and falls off very steeply at longer wave lengths. This causes exposures to be very long with this filter. This filter also requires an exposure increase of 4 stops. It would be wise to bracket your exposures.
If the exposure times become a problem then try a Wratten 29 filter which requires only a 1-2/3 stop increase in exposure and produces similar results.