Over the summer it started going brown at the bottom but now it's climbed further up the tree. I'm not sure if this is what it does because it did something similar last year but not as much as this time
Cut away the brown areas right back to areas you see starting it from. I'm afraid I have seen quite a few die in my local park over the years. These plants are temperamental as far as I see it. They seldom thrive in dense planting schemes and surrounded by other tall shrubs and trees. They prefer very sunny areas with no trapped moisture around.
The roots prefer to be in very free draining soil. If it has been planted into heavy soil, then I suspect, the roots may be suffering and possibly rotting. Care is needed in preparing the planting space to ensure there is no chance of it sitting in water in the wetter months.
It should be and remain a healthy blue-green all the way to the bottom.
Sounds like it may be a problem with the water supply in summer - if branches of most conifers die they will not grow back, but it does not always show up straight away as you can't see them wilting. Did you water it at all in dry weather?
It is also possible that it might have got too wet - root rot would have the same effect.
When you think you have the answer and if you can improve the situation and if the rest of the tree is still green, it is up to you to decide if it is worth keeping, maybe plant a small shrub in front to disguise the damage. Otherwise you have a new planting opprtunity