My outside walls felt cold this past winter and I wanted to check if they were insulated. Outside of knocking a hole in the wall is there any better way of managing the destruction to see inside the walls? If I put the hole low to the floor will I be able to see insulation or does it generally start further up and how big of a how is necessary?
I don't know of any magic solution, and what you observe in one wall cavity may not be representative of any other wall cavity. That said, I think the least intrusive method is to remove the cover plate from an outlet or switch box and try to peer past the edge of the box. You can carefully widen the gap with a utility knife to get a better view if you want and can always get an oversized cover plate to cover the widened opening if necessary.
If the homes nearby are of similar construction, ask your neighbors.
In my totally uninsulated house, the wall temp ran about 20 degree cooler than the air temp during the winter.
How hot are the inside walls when the sun is on the outside of the same area?
How old is the house?
Remove outlet plates on outside walls, and look for insulation outside the box.
Bob
Call your local electric company and ask for an energy audit. One step of that is that they'll use an infraread camera, and if the walls are uninsulated, the studs will stand right out as very dark against a bright background. The tech will have the experience to know if the walls are uninsulated or not.
It's a good idea for many other reasons, if your house is older construction.
Banty
relatively cool, but I checked the walls on the inside of the uninsulated garage and the inside wall was barely warm. so maybe the heat wouldn't transfer all the way to the inside wall.
54 years old
only one oulet gives me enough room to see outside the box. I see an empty area but I also saw something shiny like tin foil.
Turn off the electric to the cover plate you are about to remove. Bend a straight piece of wire to form a small hook on the end. Insert the wire beside the electric box and angle to the side. Twist and pull. Insulation will be caught in the hook if you have any. Repeat as many times as desired.
Note: that in most cases there is a stud on one side of the box and not the other.
Colbyt
The foil suggests the possibility of insulation. The age suggests no insulation
The wire probe and the energy audit suggested by others would both be good ideas.
Bob
You can buy oversize outlet covers, and enlarge the crack around the outlet box. Seeing foil is actually a bad sign, since the only shiny insulation in that era would be Z-fold foil. Kinda sorta a combination vapor barrier and IR reflective layer. It helped a little, but not much. I'd budget to have the walls blown. If outside is sided, they can pull 2 strips of siding, one high and one low, and do it that way. (Don't let them do it through the siding and use those damn snap-caps- even if the paint holds, they stick out like sore thumbs.) If house needs resided anyway, they can blow, plus add a layer of foam under the siding. If outside is brick, you are looking at doing it from interior, and doing a lot of drywall patching, unless you like the crown mold and tall baseboard look.
If there is a company with a thermal camera in your town, have them come out first cool day, and they can tell you in five minutes what walls and roof areas are insualated enough to notice. I wanted it done here, but no local company offers it.
aem sends...
If there's adequate insulation, an exterior wall shouldn't feel much colder than an interior wall. So unless your house was also cold, I'm guessing you don't have much insulation. But as someone else suggested, get somebody with an infrared camera and you'll know better.
Also, in some houses the wall cavities extend into the basement and aren't covered. A look down there may tell you what you want to know.
who do I call to get the house blown? Do you mean the guys who blow wet newspaper into the walls? Do all insulation experts do this or is there a separate name for this procedure? Is this process better than fiberglass?
Would it work to just buy infrared film for a standard 35 mm camera? A good camera has a separate red dot on the lens to show where to set the focus for infrared.
Would a non-contact thermometer be of any value?
Sure. With 70 F house air and Tw and Ta wall and outdoor temps and a slow-moving R0.67 indoor wall airfilm resistance and an Rv wall R-value, we have this, viewed in a fixed font:
Tw R0.67 | Rv
70 F ---www-------www--- Ta ------------>I = (70-Ta)/(Rv+0.67)
Tw = Ta+IRv, makes Rv = 0.67(Tw-Ta)/(70-Tw).
For instance, if you measure a Tw = 67.5 F wall temp with your $50 Raytek MiniTemp when it's Ta = 30 F outdoors, Rv = 0.67(67.5-30)/(70-67.5) = R10. This works for windows too. It's best done before dawn, when the outdoor temp is changing slowly.
Nick
You would also have to buy a filter for the camera so only infrared gets in. Infrared film also responds to visible light, so the filter is necessary.
The other problem may be finding someplace that can properly process infrared film, my guess is that Walmart and the local drug store would have no idea what to do with the stuff.
That kind of film won't show warm vs hot spots, and if it did, the heat in the camera would expose it, unless the camera were cooled.
With 70 F house air and Tw and Ta wall and outdoor temps and a slow-moving R0.67 indoor wall airfilm resistance and an Rv wall R-value, we have this, viewed in a fixed font:
Tw R0.67 | Rv
70 F ---www-------www--- Ta ------------>I = (70-Ta)/(Rv+0.67)
Tw = Ta+IRv, makes Rv = 0.67(Tw-Ta)/(70-Tw).
For instance, if you measure a Tw = 67.5 F wall temp with your $50 Raytek MiniTemp when it's Ta = 30 F outdoors, Rv = 0.67(67.5-30)/(70-67.5) = R10.
It's hard to measure an R30 wall this way, because the indoor wall temp is very close to the indoor air temp (69.1 F). Aiming the IR thermometer into a 1" hole in 1 ft^2 of 2" R10 Styrofoam pressed against the wall for a few minutes could increase accuracy, making something like this:
Tw R10.67 | Rv
70 F ---www-------www--- Ta ------------>I = (70-Ta)/(Rv+10.67)
with Rv = 10.67(Tw-Ta)/(70-Tw).
Rv = R30 and Ta = 30 makes Tw = 59.5.
Nick
I think I bought that, but I can't remember.
I'm sure. In NYC, I knew of a real photolab 2 blocks from City Hall. You could drop film off at 2AM and pick it up at 4AM. Probably quicker if you paid extra.
Baltimore sort of goes to sleep at night, but I'm sure in the phone book or by asking at a camera store, I can find a real lab.
On 28 Jul 2007 14:18:17 -0400, snipped-for-privacy@ece.villanova.edu wrote Re Re: how to find out if walls of house are insulated?:
Would this be valid for cooling? For example Ta=90F, Inside temp =
70F, Tw=72.5F
Sure, with no sun shining on the wall, eg at night.
That makes Rv = 4.7 (not much.)
Nick
Darn. Oh, well. (Reply postponed because I was hoping to write a more elegant reply.)
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