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Post Hurricane Sandy repairs: advice needed

Insulate new ducts? Bubble wrap or what kind? Water in crawl space solutions?

Hi, I have a small cape cod house on a lake, 2 blocks from the ocean in NJ, that was recently flooded by Hurricane Sandy. The seawater came 4' above ground level, 14" into the house.

There is a low dirt bottom crawlspace, which has water or is wet most of the time because the water table is so high.

The forced hot air furnace also handles the A/C air flow. I have been advised that the furnace and all the ductwork needs to be replaced. I've gotten mixed information on whether to insulate the new ducts or not, and if so what type of insulation (old ductwork is not insulated). There wasn't any insulation anywhere in the crawlspace.

I also had contractors recommend addressing the dirt floor and sump pump system.

I am financially strapped and need to spend very wisely. I'd like to get opinions/advice on what I should do. Any help would be greatly appreciated.


Asked by Sandy Sole
Posted Nov 30, 2012 2:48 PM ET
Edited Nov 30, 2012 3:07 PM ET


5 Answers

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Here is one opinion I found:

Re: Insulating ducts in crawl space
Don't insulate the ducts. Insulate the perimeter of the crawl space. You need the radiant heat off the ducts to keep your plumbing from freezing.

Answered by Sandy Sole
Posted Nov 30, 2012 2:59 PM ET


I have friends with a house located near a river that floods every few years. They finally got tired of replacing their furnace after every flood. They decided to move all equipment out of their basement and relocate the furnace and water heater upstairs. I advise you to do the same. Don't put any equipment in your crawl space.

Ideally, your furnace (or air handler) and all ductwork will be located within your home's conditioned space (in other words, not in the attic, and not in a ventilated crawl space). If you do that, and if you are short of funds, it's possible to skip the duct insulation.

Most reputable HVAC contractors now insulate all ducts, however, even when the ducts are installed inside your home's conditioned space. Talk to your contractor. If your contractor has never heard of duct insulation, find another contractor.

Answered by Martin Holladay
Posted Nov 30, 2012 3:02 PM ET


Thank you for your reply Martin.
The furnace and hot water heater are in conditioned space, 1st floor closet, but it is not possible to put duct work anywhere but in the crawl space. I'm wondering if duct insulation is necessary (it hasn't been insulated for the 15 years I've owned the house) then which type? One contractor recommended Big 8 bubble wrap due to the high moisture situation.

Answered by Sandy Sole
Posted Nov 30, 2012 4:18 PM ET


Ordinarily, I'd advise you that bubble wrap insulation is almost worthless, and that you should choose fiberglass duct insulation rated at R-6 or R-8. But your situation is unusual.

In effect, you are installing a sacrificial duct system, because your crawl space is likely to be flooded again. It probably doesn't matter too much what you install.

The better solution would be to install the ducts in chases near your ceiling, or perhaps in your attic (once the attic had been converted into an unvented conditioned attic). But if you can't afford to do it the way it should be done, you have to make compromises.

One other possibility: skip the ducts entirely, and install a few ductless minsplit units for space heating and cooling. Of course, you may not be able to afford that option either.

Answered by Martin Holladay
Posted Nov 30, 2012 4:28 PM ET


Even if you insulate & seal the walls of the crawlspace making it a conditioned mini-basement (recommended) you'll want to insulate the supply ducts to at least R6. Returns can be left uninsulated, but all ducts should be mastic-sealed at every joint & seam.

If the crawl is uninsulated (or even worse, vented to the outdoors) you need to insulate both supplies & return ducts, as well as between the joists (a lower performance approach which can even cost more money than sealing & insulating the walls to do it right.)

A perimeter drain to a sump, and a 10-mil poly or EPDM vapor barrier for the floor, (possibly with a 1.5-2" rat-slab to protect it) is worthwhile, as is 2" of rigid EPS on the walls, foundation sill and band joist (all joints & seams foam-sealed with 1-part foam.) To meet code, as long as it's not a storage space you can get away with an intumescent fire retarder paint on the foam rather than a full thermal ignition barrier.

The damp crawlspace is a major source of latent cooling load, and an uninsulated un-sealed crawlspace can account for as much as 25% or more of your space heating load in winter. (In most 1-story homes it would be on the order of 15-20%.)

Answered by Dana Dorsett
Posted Nov 30, 2012 4:29 PM ET

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