Thanks for your answer,

The css change you suggested just removed the icon but a small header was still visible...
I thought it would be possible to disable in the xhtml source that it doesn't have to be rendered. But i think a temporary solution is to use the display: none; css attribute, thanks for that!

How i remove the header:

xhtml:

<rich:dataTable value="#{bean.list}" var="entry" styleClass="no-table-header">
 <rich:column selfSorted="false" sortBy="#{entry.year}" sortOrder="DESCENDING">
 <h:outputText value="#{entry.year}" />
 </rich:column>
 <rich:column>
 <h:outputText value="#{entry.description}" />
 </rich:column>
</rich:dataTable>

.no-table-header .rich-table-thead {
 display: none;
}