insulation advice

[minnesota_native2000]

Would R-30 be the correct insulation for belly repair since it gets so cold in minnesota? Thought I read in mark's book to use like 3 1/2 in. insulation and R-30 is more then 3 1/2 in. thick


thanks for your help

[JD]

R-30 would be great, but the 2x6 floor joists would limit standard batt insulation to R-19.

JD

[minnesota_native2000]

Thanks JD

In your opinion does fiber glass insulation's r value degrade over time?

The reason I ask is on my belly the center is really bad, but the left and right side sections some are ok some not. Do you think I should just replace it all. Since the place is 35 years old?


thanks

[JD]

Fiberglass batt insulation does not lose a significant amount of R value if left alone. If it is compressed or water damaged, old or fresh, it loses insulation value. It is also very possible that the factory insulation is not R-19. I have seen it as small as 1.5" thick. When adding a large amount of insulation, it is best to keep the insulation thickness consistent. Air flows just like water, to the area of least resistance. A home with half R-19 and half R-13 will force the majority of air transfer to the R-13 side, channeling not only the air, but water vapors as well. In the worst cases, where the home is mostly R-19, but one area has insulation pulled out due to a regular house plumber being under your home, you could end up with a condensation problem, depending on your local climate and hvac. This is a much worse problem when insulation is missing in a ceiling or in walls with aluminum siding.

JD

[minnesota_native2000]

Thanks for all the information never knew there was so much to insulation and air.

[flcruising]

I'm in Florida, and recently added R-19 (could have gone to R-30, but not necessary here) between my 2X8 joists on half my home so far.

Basically it was a matter of slitting the belly fabric down the middle. Cutting the existing R-11 blanket insulation into strips at the joists to double it out over the outrigger areas. Then stappled paper backed R-19 to the middle. Took the time while I had it open to spray foam any electric/plumbing holes in the floor.

Doesn't get really cold here (teens at night), but the floor doesn't sound nearly as hollow. I do hope there's a difference in floor temperature once winter hits again.

[minnesota_native2000]

What's the best way for installing new underbelly material? I know the insulation must hang below the floor joists and water lines. Would stapling it up be a good way?


I've never tried anything like this. I would appreciate hearing anyone's opinion on how they did it

thank you

[flcruising]

Forgot to add...

Since all the plumbing hangs below the joist, and I now have insulation between the joists, I simply wrapped them all in the foam pipe insulation for protection. And my belly plastic was just taped and restappled to the bottom of the joists.

I think your best bet would be to insulate the floor and pipes like I mentioned, then apply new belly wrap, or a tyvek type house wrap for breathability.

The center section between the I-beams is much easier to work under than where the outriggers are. If you can just tape and staple back in those areas, it would be much less work than replacing the whole thing.

[minnesota_native2000]

Have your pipes ever froze putting the insulation between the joists? In Minnesota it can get down to -25 below zero

Half my insulation is missing and it has the buffalo board material... what's left anyway. Tyvek house wrap...Will that resist bugs?


thanks for your help

[flcruising]

I doesn't get cold here for long enough to freeze the house pipes, and it's only been since spring that I've done this, so there's been no below freezing temps. The foam insulation will privide enough protection, but your case may be different.
I do forget though that the underfloor ducts that most of you have (mine are in the attic) help for freeze protection too.

Yes, tyvek is not a food source for bugs either.

[Robert]

Tyvek will not resist bugs and it has nothing to do with being a food source.


Do NOT place the insulation between the floor joists.


The heat from the duct trunkline will do no good IF the insulation is above that.


Thanks,
Robert

[minnesota_native2000]

Thanks Robert I'll stick with the belly material and I didn't think insulation should be stuck between the joists aleast in my area.


So is stapling the material around the edge of the floor joist the best method or is there a better way?


Thank you

[Robert]

Hi,

It will depend on the water lines and any electrical cables and where they're run.


You want the insulation below the duct trunkline, water lines and electrical cables.


You also want it to hang down to allow airflow across the underbelly area.


Two best ways is to glue insulation facing (paper) to bellywrap, then install wrap with a slight to moderate sag.



Or, you can use wire attached to joists to hang down and lay insulation in across wire.


Now, if all wire and water lines are through the joists, you may can attach to bottom if it can hang enough to allow airflow evenly.


IF you do this, be sure to NOT nail or staple into a cable or water line.




Thanks,
Robert

[flcruising]

You can always add blown cellulose insulation to the belly area also. This would be much less work and may actually be cheaper than trying to replace the fiberglass. The belly may need some additional support from below which could be accomplished with some wood framing.

[Robert]

Using blown insulation in the belly area would be way more work, would give uneven airflow and in the end, would be a nightmare IF you ever had to enter belly for a repair.


Going to lock this thread now, if further info needed, please post new thread, email or pm one of us.


Thanks.


Take care and best wishes,
Robert