Pulling new heater duct

Missionstreet wrote:
Looking into replacing my old smelly heater 4" duct pipe.

Is semi rigid metal pipe acceptable substitute? The only other selection I found at the "box" store was some spiral wound "foil" pipe that feels weaker that the original existing.

Also, the sections running to the bedroom and bathroom I was thinking of pulling the new in with the old. Is this a good idea?

My concern is what looks like the existence of nails under the floor that might puncture the pipe as it is being pulled.

I believe it was all open when originally assembled on the "jig."

The ducting used in most RV's is usually flimsy and inefficient. I had to replace all mine from furnace to registers which wasn't as monumental in my TT as it could be in others.

I used a better grade of ducting that doesn't kink as easy as the factory type which seems to be just aluminum foil over a slinky.

If I were to do it again I'd use some insulated ducting like this:



With my new ducting I get more flow from the registers but a lot of heat is dissipated in areas I don't necessarily want more heat (like around the power distribution center/converter and under refrigerator) so insulation will direct more heat out into the living space.

This insulated 4" ducting is available at Lowes with a 25' piece selling for ~$40. Where the duct has to make sharp bends I'd add a metal fitting to make the bend and then just wrap it with fiberglass strip insulation and cover with Duct Tape. A little more effort and modest expense but far more efficient and easier on furnace.

As for heat in cabinet/storage areas to prevent water line freezing in cold weather, just add some ventilation louvers to the closed off areas that will both allow living area heat to travel into these spaces and also provide year-round ventilation that mitigates moisture damage.

Semi-rigid metal ducting will work but will radiate far more heat in spaces you don't necessarily want and less in areas where you do.