The additional cost of manufacture and materials mean that timber window frames are more expensive to install than uPVC windows. Timber window frames also require ongoing maintenance to keep them rot free and looking their best which is an additional cost that should be considered as part of your decision-making process.
When compared to wood frames, UPVC windows have a number of advantages for your home. Aside from the lower cost and lower maintenance, UPVC offers benefits in terms of thermal efficiency. While both wood and UPVC are thermal insulators, the construction of a UPVC frame means that there are narrower tolerances which means fewer gaps that could allow draughts and heat loss.
UPVC window frames offer benefits in terms of the level of security that they offer too - the multi-point locking systems are built directly into the frame, which means that they are harder to tamper with from outside, while the presence of hard to break double glazing panels means that there is less opportunity for windows to be broken.