Frozen pipes...help

[Mac McQuinn]

Why not replace the tile with a piece of egg crate to let the heat go up

Good idea, I'll check around and determine if it's available in my tile size, thanks.
Mac

[Lee Schierer]

Insulation just slows the passage of heat , doesn't stop it so your perfectly insulated space will eventually equilibrate to below freezing. In a worst case scenario I'd cut a floor register into the space from above to provide some conditioned air circulation into the bay with the pipes.

This is not accurate. If the space above is heated continuously, the heat flow will continue as long as there is a temperature differential. As far as cutting in a floor register, unless your provide an air return, zero air flow will occur.

The normal approach is to move the pipes as close to the heated area as possible and then insulate below and around them with adequate insulation. Insulate the entire floor (ceiling) area, nit just the bay with the pipes. The higher the R value the better. You also need to insure that you seal off any air flow from the cold space so that air flow does not negate the insulation.

[Jim Huelskoetter]

I would consider pulling the ceiling and getting closed cell foam sprayed, giving better insulation and an air barrier from exhaust gasses. But that might be tough to get done quickly during a cold spell

The existing structure has some insulation value, even if there is only the garage ceiling and floor with no insulation. The temperature at any point between the ceiling and floor will be proportional to the thermal resistance up to that point, vs the total resistance of the structure. So, if half the thermal resistance is below the pipe, then the pipe will be at half the temp difference between the ceiling and floor. That calculation shows that insulation added between the ceiling and pipe will be most effective at preventing freezing of the pipe, as others have said. Completely filling the cavity with insulation would save energy cost but insulation above the pipe would increase freezing risk.

[Jim Andrew]

I built a house once with a bath over the garage. The plumbers put the water lines really close to the lower edge of the joists. I put the pipe insulation on the pipes, and put as much insulation under the pipes as possible, but looking back should probably have put furring strips on the joists before finishing the insulation. The plumbing froze up, and the plumber fixed it, and told the homeowner it was my fault. Nobody called me. Plumber told me about it later.

[Peter Christensen]

If you can plumb in a second set of pipes back to the Utiliy room and put in a couple little recirculating pumps the lines will never freeze and the hot water will be instantaneous. Only need to turn it on for winters.

[roger wiegand]

I didn't make my point clearly. I think you want to bring the pipes inside the conditioned envelope of the house, which means putting the insulation on the cold side and allowing heat transfer by whatever means into the space where the pipes are. Conduction and radiation may be sufficient, an opening will allow convection, albeit limited, as well. Burying the pipes in insulation doesn't accomplish this in an effective way. It can work, especially for copper pipes which are good conductors, if the conditions aren't very extreme, but I don't think it's the best or safest long term solution.

[Prashun Patel]

The easiest would be to just blow insulation into the cavity without having to re-plumb. I am going to do that, and am already installing a thermostatic space heater mounted on the ceiling.

I think this is the best compromise.

[Wade Lippman]

The easiest would be to just blow insulation into the cavity without having to re-plumb. I am going to do that, and am already installing a thermostatic space heater mounted on the ceiling.

I think this is the best compromise.

Obviously you have made your decision, but I have some questions...

This seems like a disaster waiting to happen... How long has it been like this? Has it frozen in the past.
Is your garage insulated? If not, I can't see insulating the ceiling helping much. It is more likely to prevent heat from moving down from the bathroom as preventing cold from moving up from the garage.

A friend put a pipe for a pot filler in the insulated wall between their kitchen and garage. It froze the first year and they had to put heat tape around it. Your situation is much worse.

[Prashun Patel]

I take your point and am not being cavalier about this. The pipe has burst once in 17 years. The theory that the batt insulation under the pipe settled and allowed air flow through the cavity seems sound. If we fill the cavity with insulation that does not settle then the airflow will cease.

The suspenders to the above belt is the electric heater that I am putting in the space. So I am blocking the entry of any cold air from the side and making sure the above and below are always above freezing.

I am going into this with eyes wider open becaus of this thoughtful advice here.

Thanks.

[Myk Rian]

Some say to insulate the ceiling below the pipes so that the pipes retain the heat from the interior of the house.
Others say this is hogwash, and that heat rises, and that the best (for a finished ceiling) is to blow in cellulose and block all air movemement, thereby insulating the pipes from everything.

Not only is it hogwash, it doesn't make any kind of sense. Leave the pipes exposed?

I'm also planning to install a 220v electric heater as extra insurance (excuse to run 220 to my garage for some tools).

I have a Dayton heater in my garage. Something like 14k-17k BTU. I keep it at 45-50º.