Ventilating roof spaces in winter or in cold climates is still important, and will not affect the warmth of an insulated home.
In colder climates the moisture can build up quickly in your roof space.
This moisture can come from household exhaust fans from bathrooms and kitchens and combustion products from burning of natural gas.
The average family of 4 expels up to 12 litres per day of moisture laden air into their roof space.
Moisture in your house can be a destructive force, causing wood rot, mould and mildew, and so contributing to household allergies.
Ventilating your roof space will allow your house to breathe & expel the moisture laden air.
Assuming your house has ceiling insulation and the living space is not vented into the roof space, this will not adversely affect your heating bills, and you will be comfortable in the warmth of your home, knowing that moisture is not building up in the roof above your head.
For more information on the combination of Ventilation and Insulation click here