There was a brief run of episodes of This Old House that was hosted by Richard Karn from Home Improvement. I remember seeing it!
I believe this was not long after Home Improvement was canceled, Viewers complained that although Karn was still the likable guy he portrayed on Home Improvement, it wasnt very wise to have a celebrity host the show unless he was an expert in home Improvement. Karn was ill at ease at times..

Does anyone have an episode of This Old House hosted by Richard Karn? I can trade for something from my tape library. Just name a show and episode, and if I have that episode, we can trade tapes.

On Thursday, June 10, 2021 at 1:28:59 AM UTC-4, The Great Radio Surfing Channel wrote:
There was a brief run of episodes of This Old House that was hosted by Richard Karn from Home Improvement. I remember seeing it!
I believe this was not long after Home Improvement was canceled, Viewers complained that although Karn was still the likable guy he portrayed on Home Improvement, it wasnt very wise to have a celebrity host the show unless he was an expert in home Improvement. Karn was ill at ease at times.

Does anyone have an episode of This Old House hosted by Richard Karn? I can trade for something from my tape library. Just name a show and episode, and if I have that episode, we can trade tapes.

If Karn ever hosted TOH, that fact has apparently been scrubbed from the internet.
I am unable to find a single page that mentions any other hosts than the three that
the rest of us are familiar with.

The first host of This Old House was Bob Vila from 1979 to 1989.
He was followed by Steve Thomas, who hosted from 1989 to 2003.
In 2003, Thomas left the show and was replaced by current host Kevin O'Connor.

In addition, Karn's IMBd page has no mention of This Old House or even Ask This Old House.

https://www.imdb.com/name/nm0439781/