I'm contemplating doing a mantelpiece to replace a really ugly thing that I've presently got. The problem is that the one I'm thinking of as a replacement (an arts and crafts type done by Mario Rodriguez in FWW a couple of years ago) would require me to cover the outlet vents from the Heatilator unit. It doesn't really put out that much heat, The unit is at least 30 years old and is not very efficient but the cumulative effect of blocking it off might put the temperature to a not desirable (dangerous) point.
Any thoughts on this, and I realize this might not be the place to be asking? TIA for any input.