Landlords who haven't yet had their properties insulated to meet new standards may have missed their chance before Monday's deadline exposing them to a $4000 penalty.

Anthony Stone, general manager of Fletcher Building subsidiary Tasman Insulation, said although the company has no shortage of product, its installers have been booked out well in advance of the regulation change.

Stone said the company has seen a significant increase in demand for the well-known Pink Batts product to be retrofitted in rentals.

"We have sold over 50 per cent more glasswool insulation this year compared with the same time last year, and