Insulation, Radiant and Vapor Barriers - Rim Joist Insulation - Ceiling Already Finished!

Hello! Great forum here, this is my first post. My question involves insulation on the rim joist area of my 1927 home...

Last winter the floor on the first level of thios house were brutally cold. They are hardwood floors. The basement, which is directly below this level, has a plaster-and-lath ceiling installed. There are a couple penetrations in the ceiling below around water pipes and such, and I can feel the cold air rushing into the basement from this joist space.

Is there an easy way to insulate this space without major ceiling damage? I was hoping to perhaps drill a hole near the outside wall in each joist bay, and perhaps spray a slow-rise foam towards the rim joist. My goal would be to get the foam to rise and fill the end of each joist bay. I'm thinking that with proper insulation at the rim joist I may have a chance of a reasonably warm floor this winter.

My concerns are that most of the slow-rise foam instructions I have seen are clearly meant for vertical cavities - in other words cavities that are much taller than they are wide. Here I am trying to do just the opposite - I wonder if the foam will just expand away from the rim joist area before it ever has a chance to rise to the height of the joist cavity?

A little background:

I have addressed other issues with the home that I hope help with the cold floor this winter. This includes:

1. Installing as many new windows in the house as possible. All remaining windows will be covered in shrink film this fall.

2. Insulated the attic and especially the large attic hatch in the upper hallway, and weatherstripped the hatch to make it air tight.

3. Installed a fresh air intake in the basement to allow for make-up air for combustion in my 80% efficient boiler.

I'm hoping that the above will decrease demand for air to rush past the rim joist area and into the floor of the first level or through other points of inlet. This house is very tall and has a significant stack effect. It is a two story house but the roof is bult like a giant "A" frame. The distance from the attic floor to the peak of the roof is 16 feet. If any air gets into the attic I'm thinking it'll want to rise very quickly!

Thanks in advance to anyone that can help. I'm not thinking the rim joist area is a "must do" but I'm thinking it would certainly help with the "cold floor syndrome" that this house has.

Hi ferrstein, and welcome to the forum. Actually I usually put the rim joist in the must do category, but usually it is open and easy to get to. If you are willing to do some patching, the rim joist is one of the best paybacks and you have already felt the air flow so I'm sure yours will make a big difference. What you might consider is standard spray foam rather than slow rise. I think your concerns are correct that the slow rise could move out before going up where you want it. The standard spray however would start where you apply it and that might simply require a bigger hole. If you cut a 4"x4" hole with a skill saw, it would be simple to lay a board over the top, secure it, and attach a patch inside the hole. Then a nice mud job to blend all of the patches around the perimeter. Since I haven't done any foam work as yet, I can't say how small the hole can be, but as long as you can target the rim joist and sweep the space you should be all set. You can pick up the DIY foam at a lot of places.

Now, you said you felt the cold air rushing in, then you should locate the destination as well as the source you are addressing. That destination can be up the stairs and out a bath vent, through dozens of electrical outlets and ultimately into the attic and out, but it is the stack effect you mentioned that pulls the cold air in.

Check the plumbing under kitchen and bath sinks. Make sure vent dampers are clean and working. There are ball type vents that seal better. If your new windows were replacement units, you could still have some leakage around the original frames. Floor to wall cracks are often hidden with carpet. Here is a link with some tips, but you can Google "how to air seal my home" for many more.
http://oee.nrcan.gc.ca/residential/personal/documents/air-leakage-eng.pdf

Bud

Hi Bud,

Thanks for the ideas and the excellent link!

Yes, I'm thinking some bigger holes will be in order. Maybe big enough to place a mirror through the hole to see if I can see the rim joist area. I think with the right technique I can get the rim joist sprayed without major damage to the ceiling.

Even though the ceiling in this basement is finished, I do not treat the basement as a finished basement. Patches in the ceiling wouldn't bother me at all...

As for the destination... last winter air was rushing upstairs fast. Much of that had to do with a dozen leaky windows and a large attic hatch that was actually jamming and leaving a 1/4" gap all around. I didn't realize that until this spring.

Fingers crossed that I'll have a warmer winter this year!

I've been doing the energy auditing long enough now to have seen some of the results and it sure makes for happy home owners:). Not all that long ago, the recommended insulation was based strictly upon the cost of today's energy. Now, they say they are projecting 10 years or so into the future, but I don't think they are suggesting enough. Besides the cost savings, the comfort, and the peace of mind knowing whatever happens you are ready, there is what I call the "Wow" factor. You get that when you go to an extreme level of insulation and I believe it will pay big dividends one way or another. Nobody laughs at 2' of insulation in the attic or heating a home for $300 per year.

Bud