Do radiator covers harm heating efficiency?
Radiators heat by convection and radiation. The radiation output will be affected by the amount of radiated surface you cover and the convection process will be affected by how much you reduce the air flow around and thru the radiators. If the covers reduce the heat output too much you may have to increase the size of the radiators or add more heating surface. (another radiator or a larger radiator) The amount of heating reduction will be determined by the construction of the covers. Covers that have a closed top will reduce the output by as much as 30%. Design is everything.