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Floor insulation. Ideas please

We live in a dutch colonial house constructed in the 30's. At some point, a small (10X15) office was added off the living room. The room is very cold during the winter and I believe a tremendous amount of cold is from the uninsulated floor. Unfortunately, they backfilled the crawl space so it only 10-12 inches deep. Therefore, I can't insulate the crawl space in a traditional fashion. The only access I have to the crawl space is where I knocked out a cinderblock in see what was under the floor. Does anyone have any suggestions on insulating this room? I have considered blowing in a product like attic cat loose fiberglass insulation into the space. I don't see a way of using any type of vapor barrier so I not sure is I would run into moisture issues, etc. Any suggestions would be great.

Thanks Dan

Re: Floor insulation. Ideas please

I would recommend contacting an insulation installing company & see if they can blow in something like closed cell foam that would include a vapor barrier (Yellow Pages: "Insulation").

Given your very limited access hole, they may have to cut another access hole or access floor panel somewhere inside the office, perhaps in an out of the way space like a closet, etc. so they could get full coverage; if they decide that a vapor barrier is not needed, they can use something like cellulose blow-in.

Depending on your general location are you experiencing zero or sub-zero winter weather???


Re: Floor insulation. Ideas please

I would agree with Dobbs that insulation and a vapor barrier seem to be a good idea----but how much heat do you have in this room???

The room will remain cold if you don't have adequate heating elements.

Do you have forced hot water heat, forced hot air, electric---how many convectors???

Do you have a lot of glass (windows); exterior door; ceilings over 8'; exterior wall with or w/o insulation???

An initial step is to do a HEAT LOSS CALCULATION to determine if you have adequate heat in the room.

Timothy Miller
Re: Floor insulation. Ideas please

Howdy, first work on stopping air infiltration into the crawl space. Seal up any cracks with caulk an or foam in a can insulation. The hole you made in the block you need to make sure it is air tight.
It is almost impossible to insulate such a small space- no room for the installer much less the tools to install and the insulation.
Second how is the room heated is there a cold air return or any space under the door to rest of house to allow the air to move in an out of the room / assuming it is forced air heat. How much attic insulation over this rooms ceiling? Whole bunch easier to add attic insulation and seal off the crawl space....

Re: Floor insulation. Ideas please

Thanks for the replies. Answer to some of your questions.

We live in NJ so rarely gets below 20.

The room is 9x13. The room is heated with hot water baseboard radiators. There are 4 3X1 foot radiators in series. My guess it is a little underheated.

I suspect the walls and ceiling are underinsulated. I am fixing to replace the large single pane window any day now with a Pella casement window. It will allow me to see what I dealing with in regards to insulation. During the past 2 winters I have blanketed the window with packing blankets and it makes a significant difference. The reason I feel the floor is one of the problems is how cold it feels to the touch. I understand taking care of the ceiling will greatly help.

Just wanted to see what people thought about blowing in insulation. I think closed cell would be more than I want to pay right now. I got an estimate of 3-4 dollars/sf for another crawl space.

Re: Floor insulation. Ideas please

A new double-pane window is an excellent idea; also check for insulation in the exterior wall by temporarily shutting off elec. to the room & removing 1 or 2 elec. outlets in the exterior wall & using an opened coat hanger smeared with glue to probe the wall---you will hear it rattling around if there is no insulation; some insulation will stick to the hanger if present.

Good idea to have them blow in some exterior wall insulation at same time they do the crawl space.

The radiation you have there sounds adequate for a room that size---assuming the hot water going into them is 180 degrees---you can check for this by quickly touching the rads while they are in a heating cycle.

You won't be able to keep your hand on the rad for more than a second if they are at the right temp---if they are only lukewarm, you will have to address the inadequate heat issue.

Timothy Miller
Re: Floor insulation. Ideas please

Howdy again, first check the attic an determine how many inches of insulation then add more to get an R60. R 60 a little overkill but at little additional cost verses r-45 its always worth it in my mind. Blowing in cellulose would be my choice. It's the attic insulation that will help warm up the room far more the adding to the crawl space. But if you are dead set on the crawl space the get a bid to spray the walls of the crawl space little surface so the cost is way cheaper then insulating the joist cavities. If no plastic on the dirt install plastic. or if want to do if cheaper get no bat roll r-19 fiberglass and install it again along the walls of the crawl space be sure you seal any air infiltration opens too.

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