The union also criticised the “macho environment” of construction that labels those who complain about the cold weather as “weak”.
UCATT said: “The lack of care for the construction worker is virtually institutionalised in the construction industry.”
There is no current legal minimum or maximum temperature for working outside.
Unions are currently negotiating to have rules or guidance on working in extreme weather included in the Construction Industry Joint Council agreement.
An NHBC spokesperson said: “NHBC’s role is to support the industry in maintaining and improving the build quality of new homes for homebuyers. In fulfilling this role, we require builders offering the NHBC warranty to build accordance with our Technical Requirements in relation to the construction of new homes.
“We are not in a position to impose conditions on builders that do not relate to our technical requirements and we cannot influence the terms under which workers or contractors are employed.
“Legislation is in place that covers working conditions, and guidance is provided by the Health and Safety Executive that encourages employers to meet their obligations in this area. Employers have general duties to ensure health and safety under the Health and Safety at Work etc. Act 1974, which includes duties to assess and control risks from work under the Management of Health and Safety at Work Regulations. These legal requirements cover both working outside in the cold and in the sun and/or heat.”