Few comments, it has always seemed to me that given the time it takes and the effort using low quality materials makes little sense. Particle boards in every flavour are the worst material on the market. I would avoid them and spend the small amount extra to buy anything else. The issues of out gassing (formaldehyde and/or phenols) low moisture resistance, and very poor weigh to strength is enough to avoid it.

The other thing gets glossed over here a lot. You do know that generally speaking racks get ambient air temps most from the room temp. If the room temp is too far off of your preferred ambient air temps often the room needs to be heated some. There are other ways but they can be difficult.