My front door is steel with a 2’x3’ double pane window. The door feels so cold on frigid days that I’ve always assumed it’s uninsulated. Occasionally I consider taking the door off its hinges, drilling several holes in the top and bottom and trying to fill it with some sort of insulation.
Is there any chance this would work? Is there so much baffling in a “hollow” metal door that the idea is impractical?
The methods I’ve considered are:
Fiberglass pushed with a long stick through some 5" long openings (harder to make than just round holes, and any internal baffling would be a serious problem.)
“Great Stuff” foam insulation. This would require drilling holes on all four sides, and the insulation might gum up the door knob/lock (they could come out) and not reach the center of the door. And it might take $25 worth of foam.
Some sort of small insulating pellets that could be poured through the holes. I’m not familiar with this kind of product, or where I could buy it. This approach could sift through some baffling.
I can’t say about steel doors, but wood “slab” doors have cross bracing inside to keep the panels from flexing. It’s often corrugated cardboard, but it’s there.
Is there a manufacturer’s nae and perhaps model number on the door? It might be a plate attached on the hinge side, or bottom edge.
Do the panels flex if you press them hard? If they do there may be no bracing, if they don’t, it’s a good indication that there is.
I would not use expanding foam in any case. Even the low expansion stuff could cause the door to get a bulge in it.
Many insulating materials like fiberglass, foam, etc. work by trapping air and holding it in place, since air is a poor conductor of heat. Fiberglass and foam keep the air from moving around, reducing heat transfer by convection. If fiberglass gets compressed, it does not insulate as well because it isn’t holding as much air, and you might have trouble getting it in between the door panels without ‘mushing’ it too much.
Your double-panel door should be working on the same principle as the double-paned window–trapping a layer of air between the two panes reduces heat transfer. The best thing may be just to make sure the seams of the door (where the panels come together) are sealed well so that air cannot move in or out of the seams, as well as–of course–making sure you have weatherstripping that closes the gaps between the door and the frame when it is closed.
If your real real bottom line is saving on heating bills, I’d start by calling up your electric (and/or natural gas, if applicable) utility, and finding out if they have a program for free home energy audits (most do). That program sends a professional to your house who can not only look at your door, but every other part of your house, and tell you what can be insulated and where the best pay-off is. In many cases, the utility will subsidize insulation projects for your house.
OP here; thanks for the various comments. After reading the responses and pondering a bit more, it seems clear that fiberglass and foam are bad ideas.
Before I posted the question I watched a Russian (?) video of a pre-teen girl using a can opener (bayonet-style model) to mutilate a steel door and cut out the deadbolt. The inside of the door seemed filled with a warren of metal-strip braces. (Similar to the wood and cardboard in a hollow core wood door.)
I can’t find the video again, but I’ve got to assume my door is similarly constructed. The panels don’t push in readily.
What I’m going to try:
–Drill two holes in the top of the door, maybe 3/4" diameter.
–See if I can buy about eight quarts of perlite granules at a local gardening store.
–Pour the perlite in through a funnel.
–Top it off every few days for a couple of weeks as it settles into the door’s innards.
Perlite is puffed rocks. Garden stores sell it in small quantities (I hope) to loosen soil, but it also is used to insulate the hollows in concrete blocks.
I have operated heat sensing equipment and steel door are terrible about passing heat and cold form one side to another. Worse than you would ever imagine. The amount of cracks around a door are also amazing for the most part on most homes and business.
If you can stand the expense, get a quality insulated steel door if you feel you really need a steel one.
You can also drill your holes, one on each side then use tape and an air hose to see how much or how quickly the air will pass through. that will give you a good idea of what you will be able to do as far as adding insulation. Foam, itty bitty Styrofoam beads, puffer rocks, puffed oats, cheerios, what ever. Get a small whatever and see if you can shake it all the way through.
YMMV
IME, exterior steel doors are already insulated. If they weren’t, they would sound like two pieces of sheet metal banging together when you knocked on them. One way to verify this without drilling holes in the door would be to remove the lockset and have a look inside. Any insulation still may not be visible due to bracing around the doorknob, but you can drill a hole through the bracing to check for insulation if necessary.
If energy savings is your main goal, insuring that the door is properly weatherstripped to block drafts will have the greatest effect. Also, using a draft stopper, like those stuffed “snakes”, or just a rolled up towel will help considerably.
Whether your door is insulated or not, that 6sq.ft. of glass is the thermal weak spot.
Like Duckster said, install a storm door.
You can use spray foam to insulate, but you have to know what’s inside first; you need to drill a vent hole for every injection hole; using expansive foam can cause huge problems (heh) without experience, and the urethane can stain whatever it comes in contact with.
Many steel doors use foam board in their construction to keep the thin skins from flexing- the steel being a good conductor invariably feels cold.
We have a custom-made cast-iron door from Mexico. Weighs about 200 lbs. It faces the west sun and we have discovered it IS NOT INSULATED. So not all exterior metal doors are insulated. Most commercially available pre-made external doors are most likely insulated. So any updates on insulating? Thinking of expandable foam, even if it doesn’t provide full coverage, it should help some.
A cast iron door? Are you sure? That would be a lot more than 200lbs I would think.
Insulating an existing door is not ideal. Foam injection just isnt going to work. You could bond rigid foam to it and then cover that with a finish material. Its going to be thick and look weird no matter what.
Hi bohai. Original Poster from, hmm …16 years ago, checking in. I didn’t do anything to my door until November of 2024, and that was unsatisfying, but educational.
Air started leaking in around the door’s double-pane window (23 x 36”). I unscrewed the retaining frame, sliced through some caulk and removed the window. That let me see inside of my cold steel door. Pretty disappointing.
There was about 1/8” of spray insulation on both sides of the interior. The interior was braced with cardboard baffling similar to what’s used in cheapie interior doors. The baffling would have stopped spray foam insulation from spreading.
What I tried then was cutting away the baffling around the window opening with a 12” serrated bread knife. I had some 1” foam panel that seemed like it would fit well if the cardboard was removed. Unfortunately the baffling did not cut out easily or smoothly. The knife left a knobby uneven surface. I forced in a few inches of foam panel, but it bulged the door a bit. I replaced the window using new caulk and things are back where they started. I’m keeping an eye open for an attractive “Energy Star”-rated fiberglass door or similar.
Looking over the ideas offered 16 years ago, I’m still curious about pouring insulating pellets through the top (and knob opening) of the door and letting them settle over a few weeks. It would also be worthwhile to remove the door knob and check out the innards.
It was just an estimate. The invoice says “Luxury Custom Wrought Iron Single Door With Sidelight Design: Custom” It also has six windows approximately 12” h x 30” wide. Double paned. The invoice says it is supposed to have foam insulation, but my guess is that it does not due to the temp the door gets on the inside in summer./
Same reason you want windows in a wall, so you can see through it. See what’s happening on your porch, see who’s knocking on your door, see the front yard and driveway, etc.
You could use expanded foam pellets for bean bag chairs. Or Perlite, a mica product made just for this use. I filled the hollow cinder block walls in my utility room with Perlite.