Can the Halo damage the fabric of the interior or valuable objects and artefacts or cause delicate surfaces to expand?
No, there is no risk of damage from the Halo. The radiant wavelength is similar to that which humans radiate, and the measurable surface temperatures are no greater than they would be through human contact. The feeling of heat is similar to that of the heat of the sun through a window and there is no additional risk of differential expansion than that. (Conversely, this has previously been a risk from using quartz ray/near IR type heaters and is also true of radiators).