They received numerous design awards and commendations from the Royal Australian Institute of Architects and won the competition for the Reserve Bank of Australia Building in Canberra in 1962.
Later, Howlett came to Melbourne to continue his career as a Senior Design architect with Bates Smart and Mc Cutcheon.
In Melbourne, together with Donald Bailey, who soon to be his co-operator, they won the new Perth City Council administration buildings competition.
After suffering from a major stroke in 1993, his life was rely on the wheelchair and he mainly using oil pastel and paper to keep expressing his creativity through forms and colours.
An exhibition at Perth Galleries in 2002 displayed his art works and told the story of his memories, past and present.
The façade is constructed with windows curtain system and T shape sun hoods which provide effective use of artificial and natural lighting.