GOV.WALES uses cookies which are essential for the site to work. Non-essential cookies are also used to tailor and improve services. By continuing to use this site, you agree to our use of cookies.
Definition: Blaenoriaethu effeithlonrwydd ynni adeilad o ddechrau'r broses ddylunio a datblygu, ee wrth bennu'r cynllun a'r deunyddiau ar gyfer yr adeilad, yn hytrach nag ychwanegu nodweddion arbed ynni ar y diwedd.