Insulation Dilemma - Need Help

[cabinetman]

We are in the process of re doing the ceilings in the front half of the house. The roof is a flat deck and the rafters are 2x6, 16"OC. The present situation is that inside there is a layer of 5/8" plasterboard and then a 12" square, 1/2" T&G ceiling tile.

Our choices are first: To leave the existing two layers and add a third layer of 12" ceiling tile (new), OR-

Tear down the two layers, install R-19 fiberglass batts and add one layer of ceiling tile (new).

Which would offer the best insulation?

[big tim]

I think the R-factor of a fibreboard type celing tile is probably less than 2. I'm sure you would get better insulation with the fibreglass bats.
One other thing to consider though is fire protection. Not much protection out of a layer if fibreboard style ceiling tiles.
My 2cw

Tim

[Jeffrey Schronce]

Tear down 2 layers, install R-19 minimum rough in drywall and layer of ceilng tile. There is no comparison to modern insulation versus gypsum/lathe/plaster applications.

I have no idea where you are located thus not sure if you should move to a higher R factor which will fit in 6" stud. R-21 will fit and if you can find R-23 it will fit as well.

What type of roof surfacing do you have on the other side?

Remember, that part or all of your remodel may be eligible for Federal Tax Savings under IRS provisions.

[LCHIEN]

Tear down 2 layers, install R-19 minimum rough in drywall and layer of ceilng tile. There is no comparison to modern insulation versus gypsum/lathe/plaster applications.

I have no idea where you are located thus not sure if you should move to a higher R factor which will fit in 6" stud. R-21 will fit and if you can find R-23 it will fit as well.

What type of roof surfacing do you have on the other side?

Remember, that part or all of your remodel may be eligible for Federal Tax Savings under IRS provisions.

I don't really know but Jeff's ideas all sound a lot better than no insulation except for the fiberboard and gypsum...

[Hellrazor]

Will the use of R19 allow any air flow to help cool the flat roof? Improper insulation can cause premature failure of the roofing.

[steve-norrell]

Up here in God's country, adequate air flow above the insulation is critical unless you want to deal with all kinds of condensation and ice problems. We just went through a remodel that changed air flow in the attic and did result in some problems. Air circulation above the insulation really is critical.

There are probably similar issues in Florida and it may be better to have air movement and ventilation above the ceiling than it is to have it stuffed with insulation. Over-insulation may create more problems than it solves. I would consult a reliable heating / cooling contractor or builder on local practice.

Good luck, Steve

[Russianwolf]

Guys, he's in Southern Florida!!!!!

R19 is plenty unless you are having a problem keeping the AC in. But I would go with Fiber as insulation helps keep heat out of your house. you will probably see a drop in your AC electric.

[Hellrazor]

He still needs to ensure proper air flow above the insulation.