The limit on a remortgage is usually 85% LTV. So, if the house was valued at 100,000 the most you can remortgage to would be 85,000 --- so, say the outstanding mortgage was 81,000, available equity would be 4,000 ( less than the 5,000 de minimis) so the house would be excluded and the IVA end without extension. If your outstanding mortgage was, say, 79,000, available equity would then be 6,000 --- so you would need to attempt to remortgage to release this equity --- this will, in all likelihood, fail, and you will be required to extend the IVA by 12 months. All the foregoing on the assumption that you have the usual, standard, equity release clauses.
My opinions are merely that .. opinions based on experience. Always seek professional advice.
IVA Completed 23rd July 2013 .... C.C. 10th January 2014