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Discussion Starter · #1 · (Edited)
I posted last year about my two-story house in New York State built circa the 1920s that was seemingly getting progressively colder in the winter months, and whether attic insulation--of which there was virtually none--might help resolve the issue. The consensus was that it was a good idea but that cool air might be infiltrating elsewhere in the house.

Well, that was pretty spot on, as I went ahead and had cellulose blown in this week (15 inches to R-49 value, plus air sealing, etc.) and have observed no noticeable difference in the home's comfort level.

The forced-air gas furnace will kick on, raise the temperature to the programmed 71, and the rooms will be comfortable while the vents are blowing. Within a few minutes of them kicking off, my skin feels cold and the house cool.

I have:
- Installed new windows on the first floor (Okna, presumably energy efficient).
-Weather-stripped the front door. (Back door leads out to an unheated back porch, but I don't feel any cool air coming in.)

- Looked for open holes in the basement subfloor and sealed with foam.

Thus far, I still cannot tell where cool air might be coming in. But I do have a theory.

After digging around in the basement yesterday, I noticed a curious foundation element. It's a concrete block foundation. Above the basement windows is another, separate row of concrete block that has the cells of the blocks exposed in the overhang. All of them are stuffed with fiberglass batting. I pulled out the batting to find that someone--I'm guessing decades and decades prior--had stuffed the cells with insulation as well as old newspaper and even some rags. The cells seem to go on for two, possibly three feet, extending either right up to the subfloor or maybe even a little past it. When I removed the batting, I could feel a rush of cold air coming in.

Is it possible these poorly-insulated cells are my problem and that the house has gotten progressively worse over time as this DIY job has deteriorated? If so, I'm not sure whether to stuff them with more batting, rock wool, spray foam, or something else. I'm also not sure if it's just the cells over the windows or all the cells, but most every other portion of the basement has some kind of top coat and only the cells above the windows are accessible.

The contractor has offered to spray the rim joist with foam, but I'm hesitant to keep throwing money at a problem, especially if the foam would do nothing about the cells. (I also don't have what I would consider a typical rim joist--there are no cross-beams, just a wood sub-floor support. In other words, I couldn't shove any rigid foam into the joist because it doesn't have those type of spaces.)


Has anyone encountered anything like this? Do all concrete block foundations leave the cells unfilled? Concrete is, I understand, porous, and it seems like there's only a couple of inches of block and some aluminum siding separating my house and basement from freezing weather.
 

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Just turn up the thermostat.

Installing insulation will result in using less fuel to heat the house, but will do little to making it feel warmer. If standing near a window, you will radiate less heat through a good window -- that might be perceptible.

Don't get hung up about the number on the thermostat --- its not a NASA grade instrument. 74F on your thermostat may not be the same as 74F on your buddy's.
 

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Have you installed gaskets in all of the exterior wall electrical outlets? Mine used to be a source of cold air during winter until I did this. You can also rent a thermal camera from certain orange apron stores.
I'll bet your home used to melt the snow on the roof within a few hours before the additional insulation was added. The next time you get any new snowfall, see if the snow on the roof melts. Probably not. And lastly, keep track of your winter heating costs and compare it to last year once the season is over. You'll probably be pleasantly surprised.

https://www.homedepot.com/tool-truck-rental/Thermal-Camera/FLIR-i7/
 

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A house that old may or may not even have any insulation in the walls.
Have the rim joist been sealed?
Insulation under the floor?
I'd bet when they installled those new windows no one removed the trim on the sides of the window to fill in the old window weigh pockets leaving you with a huge empty space letting in cold air.
Balloon wall framing?
If so those walls are open from the basement to the attic until someone installs blocking.
 
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Surface temperatures can impact comfort - when the heat is on the air from the vents warms up surfaces, when it shuts off they cool down.

There's a reason why registers are put on exterior walls below windows.

Some old houses have the vents on the interior so the exterior surfaces never get warmed up and the perimeter is cold.

Oversized furnaces can also create comfort problems, quickly warming up the air and satisfying the stat before the surfaces get a chance to warm up.


Air leakage can definitely make a house cool down quick after the heat shuts off.

The house could have more than one problem.
 

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Discussion Starter · #8 · (Edited)
Thanks to everyone who has responded. Here are some photos of the basement:

As you can see, there's no rim joist to speak of--at least, not one where rigid foam could be placed. The concrete blocks sit over the windows with the cells hanging overhead. You can see some of the insulation peeking out. The third photo shows how the foundation was constructed. Some batt insulation is stuffed between the concrete blocks and the beginning of the subfloor. (Or the sill plate?) The block cells aren't accessible in most of the basement.

The last photo shows the same window from the outside. I was able to stick a two-foot metal pole into the holes, so it appears the cells extend well into the living space. They all look to be filled with batt insulation, but if my understanding is correct, stuffed-in fiberglass has no insulation or air barrier properties at all when compressed like this.
 

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Discussion Starter · #9 · (Edited)
A house that old may or may not even have any insulation in the walls.
Have the rim joist been sealed?
Insulation under the floor?
I'd bet when they installled those new windows no one removed the trim on the sides of the window to fill in the old window weigh pockets leaving you with a huge empty space letting in cold air.
Balloon wall framing?
If so those walls are open from the basement to the attic until someone installs blocking.
No insulation on the rim joist. I've been told I can spray foam it, but not sure how much difference it might make with the concrete block cells behind the rim joist letting in cold air.

No insulation under the floor that I know of.

I'm almost certain you're correct about the weight pockets. The windows were original to the house. I had a well-regarded installer perform the work, and I know they stuffed batting around the window opening, but I agree it's very unlikely they did anything with the weight area. I don't know how to access that once the window is in place, though.

I don't know if I have balloon wall framing. If my walls are open basement-to-attic, how would blocking work?
 

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Discussion Starter · #10 · (Edited)
Surface temperatures can impact comfort - when the heat is on the air from the vents warms up surfaces, when it shuts off they cool down.

There's a reason why registers are put on exterior walls below windows.

Some old houses have the vents on the interior so the exterior surfaces never get warmed up and the perimeter is cold.

Oversized furnaces can also create comfort problems, quickly warming up the air and satisfying the stat before the surfaces get a chance to warm up.


Air leakage can definitely make a house cool down quick after the heat shuts off.

The house could have more than one problem.

You're correct. Every single warm-air furnace vent is in an interior wall.

I can't say whether the furnace is oversized. It's been with the house the entire time I've been here, over a decade, and I haven't always had the cold-air problem.

However, I think the furnace is part of the issue. I checked the thermostat the other day and the AA batteries powering it had corroded. It's possible that's led to some miscommunication between the unit and the furnace. During the cold snap Thursday and Friday, the furnace was cycling on for about 10 minutes and then off for 20. I don't know if that's long enough to warm up the perimeter. I don't think that qualifies for short-cycling, either, but something may be going on.

I was also thinking of setting the fan from Auto to On to help keep warm air moving toward the perimeter. Unfortunately, while the thermostat has that option, turning it on doesn't keep the fan running.

Additionally, I closed one vent upstairs while doing some renovating a few months ago. Now I see that closing even one register can cause the blower to work more to counteract the increased air pressure.

I plan to have the furnace and thermostat inspected, though I still suspect these concrete block voids are part of the issue.
 

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No insulation on the rim joist. I've been told I can spray foam it, but not sure how much difference it might make with the concrete block cells behind the rim joist letting in cold air.

No insulation under the floor that I know of.

I'm almost certain you're correct about the weight pockets. The windows were original to the house. I had a well-regarded installer perform the work, and I know they stuffed batting around the window opening, but I agree it's very unlikely they did anything with the weight area. I don't know how to access that once the window is in place, though.

I don't know if I have balloon wall framing. If my walls are open basement-to-attic, how would blocking work?
The window was likely a hopper so it would never had had weights.


Usually the rim joist sits on the wall, occasionally we build like you have to raise the dirt level on the outside. But we move that first joist over to give the insulators a chance to get in there.

You have ship lap for sup floor and every crack between the boards will allow air movement.
There is not much you can do about the block wall and the longer you have cold the deeper the frost goes and that wall looses whatever heat it is getting from the ground.
 

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With slab on grade house here, they do a peel and stick over the joint between wood and concrete and then add a foam board from the frost depth up about 6" above the top of the concrete.

For your house you might consider foam on the outside behind the siding for the whole house.



 

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You do have a rim joist, it's the wood in the pics.

They used fiberglass to stop air leakage between foundation and rim joist - it's dirty indicating air is flowing through it.

I would remove the fiberglass and fill with foam.

You can probably glue rigid foam or roxul board to the rim joist. Foam can not be left exposed due to the fire risk.

If your foundation doesn't have major moisture infiltration issues, can put 2" of roxul board directly on it.

Roxul board doesn't have high r-value per inch but the first R5 to R10 saves the most energy - beyond that the money is better spent elsewhere in an old house.

You can look at relocating the registers to the perimeter at least on the main floor - lots of $$ though.

10 minute on/20 minute off furnace cycles in extreme cold indicates an oversized furnace. Most furnaces are oversized though.
 

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Have your thermostat wiring changed so you can keep the fan running. You may need to add a relay in your furnace to do so. And pick up one of those cheap $20 infared thermometers with the laser and snoop around your perimeter with it and look at the temperatures. You may have a big leak you can't find. Is your basement ceiling (upstairs floor) insulated or finished? You may want to have your supply vents moved to where they can do a better job of circulating. And I suspect you have an older furnace.
Insulation helps a great deal in most situations. You problem could lie elsewhere.
 

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Running a regular furnace blower continuously can really increase the electric bill even on lowest speed.

I wouldn't do it without an energy efficient ecm motor - in a new furnace or if the existing furnace isn't that old retrofitting into existing. (mars azure, gentec evergreen, emerson ecotech)
 

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Discussion Starter · #17 ·
You do have a rim joist, it's the wood in the pics.

They used fiberglass to stop air leakage between foundation and rim joist - it's dirty indicating air is flowing through it.

I would remove the fiberglass and fill with foam.

You can probably glue rigid foam or roxul board to the rim joist. Foam can not be left exposed due to the fire risk.

If your foundation doesn't have major moisture infiltration issues, can put 2" of roxul board directly on it.

Roxul board doesn't have high r-value per inch but the first R5 to R10 saves the most energy - beyond that the money is better spent elsewhere in an old house.

You can look at relocating the registers to the perimeter at least on the main floor - lots of $$ though.

10 minute on/20 minute off furnace cycles in extreme cold indicates an oversized furnace. Most furnaces are oversized though.

I can definitely remove the fiberglass between the foundation and rim joist, but I'm not sure if I can just fill it with cans of spray foam or if the expansion could cause problems with either one.



If I glue rigid foam board to the joist, how could I cover it so it's not exposed?


Is it worthwhile to try an fill the concrete block voids in some way? I guess I could only even try and fill the voids that are accessible. If I have others--I'm sure I do--I can't reach them. But isn't trying to insulate the rim joist a waste of time with the voids being a factor?
 

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Although attic insulation helps, the statistics show that attics are responsible for about 25% of heat loss in the winter. The other 75% is through leaky windows and doors and of course poor wall insulation. Do you know what's in the walls?
 

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Do you have a fireplace(s)? The more insulation, new windows, vent closures, etc. that is done to a house, will make the opening of the fireplace seem like an open window in the home. There is a trend, to "seal the envelope" of the house for better energy savings. This is good, until the last opening is closed up...the fireplace.
I suggest an insulate cover for the fireplace. You can use a foam board, a chimney balloon, insulated magnetic cover, plastic window film. Whatever you can make or buy, just cover the fireplace and you will be amazed at the difference.
 
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