Building Codes and Inspections/Crawl Space Situation



I have a vacation home in New Jersey, several blocks from the Atlantic Ocean.  Last year the crawl space was flooded because of Hurricane Sandy.  I had a company remove the wet insulation, apply anti-mold chemicals and dry the space.

I still need to replace the outside air conditioning unit and ductwork in the crawl space as well as have the electrical wiring running through and from the crawl space replaced, but I am waiting for possible financial assistance.

Since I'm only there occasionally, I usually turn on the heater (low, around 55 degrees) when the temperature is forecast to get below 32 degrees, to keep the pipes from freezing.  Is there any danger from the heater running with the ducts uninsulated?  


ANSWER: Ed, sorry to hear of your situation there. There's a lot of people in that area with Their hands full right now with rebuilding.

The problem with running your HVAC system without insulated ductwork is primarily efficiency, as the heat loss will allow heat to be robbed before it gets to the intended living space. It will be more expensive to heat, although heat loss will help keep that space from the gathering moisture again. In the humid summer weather, the danger would be that your air conditioner would run and the ductwork will sweat due to condensation on it which could have long term deterioration problems, and again with efficiency in terms of high operating costs.

One solution you might explore is to insulate the perimeter walls of the crawl space and the space between the floor joists at the ribbon board, which then brings the crawlspace area within the thermal envelope of the home, So you don't need to insulate your ductwork, which will also keep the crawlspace drier.

Best of luck..

---------- FOLLOW-UP ----------

QUESTION: Thanks for your response.  I do realize that the HVAC system will be less efficient uninsulated; my main concern is that the additional heat would be too warm for the surrounding wood or wiring and possibly cause a fire.  I'm not there overnight that often, so right now it's more important that the pipes don't freeze rather than the living space be warm enough.  Hopefully I can get everything repaired/replaced before next summer.

The house was built around 1950 and I don't believe the crawl space was originally insulated, only around the ductwork.  The attic has a minimal layer of "cottony" insulation.  I thought there should be insulation under the main floor, which is cool in summer and ice cold in winter (which I can feel if barefoot.)  I asked an inspector who checked the damage if it should be insulated -- he said to leave it the way it is; if it floods again and the insulation gets wet, that could cause more problems with removal and keeping moistiure in and around the wood, creating mold issues.  Someone else said it should be insulated, for better efficiency and "they can encapsulate it so it's more resistant to any moisture or flooding in the future."  (Another option would be to raise the house, which I would not consider.)

What is your opinion?

If it were my home, I would insulate the perimeter walls in the crawlspace so the ductwork is within the thermal envelope of the building, then leave the ducts uninsulated, which will dissipate moisture. The encapsulation refers to closed cell spray foam insulation which could also be installed on the perimeter walls, which must be treated or covered with another material for fire resistance.

I apologize for the late response, I just saw your message. I have no idea why the system didn't notify me it was there.

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Keith Fuller


I'm an ICC Certified Master Code Professional fielding general building code questions. My experience has been heavy in fire related issues.


I've been employed since 1985 as an inspector and plan reviewer, and am a municipal Assistant Building Official and Deputy fire Marshal. I've had fire service experience since 1972, having served as a three time Fire Chief and Fire Marshal in years past. The increasing workload, mandatory certifications, and continuing education requirements in recent years have caused me to concentrate my efforts on code related issues. I hold national fire service certifications as well.

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