You would be expected to try to remortgage to release a proportion of the equity at some point in the final year of an IVA.
Usually if you cant remortgage then the IVA could be extended for a further 12 months.
It really does depend upon the terms of your own IVA. If your case has been put forward using the IVA Protocol, then an eventual sale of the property is likely to be avoided - but speak to your own IP if you are already in an IVA.
IVAs these days are designed to protect the family home from creditor claims, but you may need to be prepared to re-mortgage or extend the IVA by one further year to make payments in lieu of equity.