Insulation Falling Pier And Beam

[Lalo]

Hello! We recently bought a pier and beam house in the country outside Houston. Inspector pointed out that the insulation under the floor was falling; she said it should be a simple matter of nailing it back up. But the house is only 10 years old. There aren't any obvious moisture issues, like standing water, but I wonder why that insulation is falling. It seems like moisture might be a factor, no? They put fiberglass roll insulation between the joists, and then nailed insulated sheathing along the bottom. The sheathing is falling down in places, and the fiberglass spilling out.

What should I do? Should I just try to nail the sheathing back up? Remove the fiberglass on the assumption that is collecting moisture and then nail the sheathing back up? Or should I just rip out all the insulation, figuring mold and critters are bigger problems than drafts? I guess I could throw up my hands and call an insulation professional, but I'd prefer to not spend that money.

This is a weekend home, so energy conservation is not quite so critical, particularly not in winter. But if having a well-insulated floor would save us $50 a month in the summer, it would certainly be worth getting it done right.

Any thoughts?

[Mr. Chenevert]

You actually want to remove that insulation. It traps moisture and causes the hardwood floors to buckle on the first floor.

Builders are required to install the insulation per code, but make it easy for the homeowner to remove once the house passes inspection.

[Lalo]

That's actually my inclination. But would it affect my summer AC bills much? I've read conflicting things.

Thanks for the quick reply.

[musicman]

That's actually my inclination. But would it affect my summer AC bills much? I've read conflicting things.

Thanks for the quick reply.

for a weekend home, it won't make a big difference at all. i personally would remove it. what are you calling insulated sheathing? if moisture is somehow trapped in the cavity that could be making the problem worse.

[Lalo]

what are you calling insulated sheathing?

It's a solid board. I believe it's 4x8. Sort of like this http://insulation.owenscorning.com/homeown...ts/propink.aspx except mine are silver on the outside. You see them at the box stores, big silver sheets about (or exactly) the size of a plywood sheet. Normally used on exterior walls, I guess.

So if you go under the crawl space and look up, that is all you see, these silver panels nailed to the joists. At least that's all you saw before they started falling down. Now you can see the joists above them, along with the fiberglass roll insulation falling down. Now they are perfect bridges for termites and mice, etc.

[musicman]

remove it! you're asking for problems long term.

[BryanS]

Nothing wrong with having an insulated floor.

You may want to remove the foam core, and simply get some chicken wire to hold the insulation up under the floor.

Or.... just chicken wire over the whole thing, as-is.

[cgallagher]

The insulation should be flush against the floor. There are a number of ways to secure it properly, foam board is not one of them. This installation sounds like trouble, you may trap moisture within the subfloor. Remove the foam board, and reinstall the insulation with chicken wire, or they make a plastic type screen, which I think works better.

[musicman]

my neighbor had the wire/insulation setup and had to remove it because of moisture/deterioration issues.

[cgallagher]

People often install paper faced insulation with the paper against the subfloor. This creates a vapor barrier that can trap moisture and create rot. You should not use paper faced batts in a crawl space installation.

[travelguy_73]

What about blown-in Celbar? We have an uninsulated crawl space and were told that this is a good insulation option (it is similar to what we have in the attic).

[musicman]

paper in a high moisture area is just asking for problems. do you have good ventilation or only occasional vents? is there ever any water under there?

[jm1fd]

I'm thinking that "sheathing" is covered with foil. If so, the foil is keeping most of the moisture away from the wood/fiberglass.

Pull a sheet or two of the "sheathing" down and see if there's any evidence of mold or moisture. If not, put it back up....and use some tar paper nails with big plastic heads to nail it back up with. That'll help prevent it from falling down again in the future.

[innerlooper]

Different P&B houses have different outcomes with subfloor insulation, vapor barriers, vapor retarders, crawl space ventilation, etc. Some folks swear by fire-and-ice shield between the finish floor and the subfloor. For others this is the path to high dollar litigation. The question is, where is the dew point in the floor assembly in August after a week of rain and you are running the central air and the ceiling fans and cooling the floor.

Best practice (IMHO) would be to use the thickest batt insulation you can readily get (probably 8" unfaced) make sure it is flush to subfloor (as noted above), and hold up firmly with chicken wire or that plastic mesh. A pneumatic 1/2" crown stapler is great for this. Wear hearing protection. Some of it is still going to sag in places, and the possums et al will find some nook to get into and mess up. Keeping the crawl space dry and ventilated is important here. If there is a brick wall around the base, then install as many vents as you can. Ideally you would "dome" the crawl space grade, install plastic sheeting, and cover with pea gravel.

If the floors start to cup, you may need to change the plan.

BTW you need to look at the foam core material to see if it says "This material must be covered", because of flame spread. Take a piece and light it (away from the house) and if it takes off, it shouldn't be left uncovered under the house.

Without floor insulation there is almost no way to comply with modern energy code, even with triple argon windows. That sixth face will get you every time. You can download a great free energy code program from here:

http://www.energycodes.gov/rescheck/

[musicman]

If the floors start to cup, you may need to change the plan.

started out nicely.

[innerlooper]

started out nicely.

Back in the day the flooring contractor would bring the strip flooring to the location and leave it lying around (inside) for a few weeks to let it achieve equilibrium moisture content. Today pilferidge and the need for quick in and out subcontracting does not permit this. In a remodel I would recommend doing this if possible.

Some Heights builders in the past 15 years were having to go back to their two story "Victorians" to resand the cupped downstairs floors. It was not predictable which houses would cup and which wouldn't. This added to the general confusion and there is still no absolute way to predict downstairs floor behavior, and no generally accepted standard regarding vapor barriers, vapor retarders, etc. In the old days they would put rosin paper or felt in, but they didn't have AC back then and less of a condensation problem.

[Marksmu]

So - there is no consensus on what will prevent cupping downstairs? My house has the fiberglass batt being held up under the piers by small hangers that are bowed in a U - just pushed up between the floor joists...My downstairs floors have cupped and are being resanded this week - I was told to put a 6 mil polyurethane layer under the entire house and that will solve the problem. That came from an Engineer who inspected it, and he was quoting the wood floor manufacturers association. The house has a brick veneer, but it has a large vent every 8 feet or so on all sides. Also there is never any standing water under the house, and even when we got all that rain a year ago the ground beneath stayed dry.

Anyone tried this? Heard of anyone doing it?

[musicman]

So - there is no consensus on what will prevent cupping downstairs? My house has the fiberglass batt being held up under the piers by small hangers that are bowed in a U - just pushed up between the floor joists...My downstairs floors have cupped and are being resanded this week - I was told to put a 6 mil polyurethane layer under the entire house and that will solve the problem. That came from an Engineer who inspected it, and he was quoting the wood floor manufacturers association. The house has a brick veneer, but it has a large vent every 8 feet or so on all sides. Also there is never any standing water under the house, and even when we got all that rain a year ago the ground beneath stayed dry.

Anyone tried this? Heard of anyone doing it?

i've heard of this only for cases where the house has a veneer all the way to the ground such as yours where airflow isn't as great. one thing that may help is putting a fan activated by moisture level to force airflow under/out the crawlspace.

a homeowner in houston country club told me a few weeks ago that they're having so much moisture right now that water is running down their walls in certain portions of the house...and only one vent.

[cgallagher]

Someone early said "Fire and Ice" underlayment should be put down between the wood and the subfloor. I believe that is currently the best practice.

I cannot believe an engineer told you to install 6 mil visqueen under the house. That guy should have his license revoked.

There is nothing wrong with having the wires to support the insulation, there are better methods that allow the insulation to sit flat, but it is very labor intensive. They probably used the wires becuase the insulation has less depth than the floor joists, and the insulation needs to sit flush against the plywood subfloor.

Did they install paper faced batts with the paper against the subfloor? This can cause a moisture trap that will swell the plywood subfloor and effect the wood above.

[Marksmu]

Someone early said "Fire and Ice" underlayment should be put down between the wood and the subfloor. I believe that is currently the best practice.

I cannot believe an engineer told you to install 6 mil visqueen under the house. That guy should have his license revoked.

There is nothing wrong with having the wires to support the insulation, there are better methods that allow the insulation to sit flat, but it is very labor intensive. They probably used the wires becuase the insulation has less depth than the floor joists, and the insulation needs to sit flush against the plywood subfloor.

Did they install paper faced batts with the paper against the subfloor? This can cause a moisture trap that will swell the plywood subfloor and effect the wood above.

The insulation on my house is just batt type fiberglass insulation there is no paper backing on it. You are correct about the wires to hold it up there - it is only about 6" thick and the floor joists are all 2x12. What problem would putting poly on the ground cause? As I mentioned earlier the ventilation is sufficient it has a 2 ft x 3 ft opening every 8 feet or so and the height from the ground to the bottom of the 2x12 foundation is about 4 feet, and there has never been any standing water - even in the worst rains. The house has gutters all leading to french drains which take the water to the ditch.

What is the downside to the poly on the ground?

[cgallagher]

On the ground is no problem. I thought you meant stapled to the underside of the floor joists. I guess he's trying to limit the moisture that escapes from the dirt directly under the slab. I'm not sure that will solve the problem. As long as the AC runs the pressure inside the home is lower than outside. The pressure wants to equallize and the humid air will travel into the home through the path of least resistance, which may be under the floor. The "Fire and Ice" or "Ice and Water Shield" creates a highly impermeable vapor barrier that does not allow moisture from under the house to migrate through the floor system. It's also used on second floors above garages.

If you have a situation where they have installed R19 under the floor with wire rods, there are probably several areas where the insulation is thin and this allows the air to move more easily into the home. Thicker insulation can create an air barrier without creating a vapor barrier - this is what you want. You could add one more layer of unpapered R19 (6") insulation. Secure with chicken wire or similar and do not compress.