# Why is the Outdoor Low Temperature (ODL) not changing after I've amended it?

[Changing the Outdoor Design Temperature (ODT)](https://help.heatpunk.co.uk/books/faqs/page/how-do-i-change-the-outdoor-design-temperature-odt-for-my-project) does not affect the Outdoor Low Temperature (ODL) used in the performance task. This task is based on MCS 031, which states the the ODL from Appendix A must be used. MCS 031 Appendix A is equivalent to the 99.6th percentile from MIS 3005 D.

**The ODL is not the same as the ODT used for the design**, which you may adjust within MCS rules stated in MIS 3005 D. [Read here](https://help.heatpunk.co.uk/books/faqs/page/how-is-the-outdoor-design-temperature-odt-set "How is the Outdoor Design Temperature (ODT) set?") for info on how Heatpunk sets the ODT.