The part that indicates that a garnishee cannot garnish a housing development account is found in the discussion about the nature of the account and the applicable legal principles. Specifically, it states that the retention sum in a construction contract, which is similar in nature to certain security accounts, could not be garnished because it was subject to a "clean bill of health" regarding defects in the construction. This analogy implies that certain types of accounts, such as housing development or retention accounts, may be protected from garnishment under specific circumstances.

While the exact phrase is not explicitly quoted in the provided summary, the reasoning suggests that accounts designated as security or retention accounts related to housing or construction are not subject to garnishment because they are considered protected or not yet due for payment until certain conditions are met.

In summary, the part of the document discussing the non-garnishability of certain accounts states that the retention sum in a construction contract could not be garnished due to its protected status, which can be analogized to housing development accounts in similar contexts.