# Cutting groove in Polystrene or styofoam sheets



## dalec (Oct 3, 2007)

I started a forum topic on homerefurb on this topic, but did not get a good answer. It may have been how I articulated my question.

I am interested in insulating my garage door. It is a typical uninsulated garage door. I have considered various garage door insulation kits, including bubble wrap sandwiched between foil, poly foam sandwiched between foil and polystrene/sytrofoam sheets. I don't want to spend a lot of $'s on the job, so am looking at using 1" polystyrene sheets cut and inserted into the sections of my overhead garage door. In order to insert the 21" x 48" panels, I will have to bend the sheets to slip them into the door section framing. I have seen one such kit include sheets grooved to the sheet to allow the sheet to be bent to slip into the frame.

I initially thought about routing out the grooves, but it could be pretty messy. Does anyone have any ideas on how I might cut the 1/8" to 1/4" wide grooves with some control over the mess? Not sure if using a router is best or would even work without melting the foam?

Dalec


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## pommy (Apr 17, 2008)

Hi Dalec

Have you thought about using rockwool fibre roll with foil backing

andy


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## Julian (Sep 30, 2008)

You could always just score the foam with a utility knife. It would be clean, and mess free.


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## dalec (Oct 3, 2007)

Andy, haven't thought about rockwool with foil backing. How would you suggest securing it to the door?

Julian, I suppose scoring in a "v" pattern will remove enough material to allow the sheets to bend without necessarily breaking and also not create a snow-like scene in the garage in the process.

I am leaning toward the scoring idea.

One day I will be able to work in the garage with reasonable comfort and perhaps even be able to do some finishing without having to set up in the living room.

Thank you both.

Dalec


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## Zuki (Mar 28, 2007)

Score with a SHARP utility knife and then crack out the bits.

I found that styro tends to dull the blades rather quickly for some reason. Unless you want to clean up an awful mess stay away from a router or saw. I insulated my entire garage with 1' styro by laying the 4×8 sheets flat on the floor, using a piece of 1×3x8 strapping for a straight edge. I went through several blades. You can tell when they get dull as the styro starts to chip out. It would normally take about 2 passes with a sharp knife to get a clean cut.

hope this helps.


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## dalec (Oct 3, 2007)

Thanks Zuki.

How effective was the 1" styrofoam for insulation?

Dalec


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## Zuki (Mar 28, 2007)

Its 1/2 as good as 2" and twice a good as nothing. 

Seriously though it did make a difference in keeping the heat in. My shop is 16×18 and I can use two plug in 1500w electric quartz heaters (the ones that glow orange) and its warm enough to work rather comfortably.

For the amount of time I spend in the shop in the winter and considering the minimal cost involved, it was worth it.


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## Zuki (Mar 28, 2007)

Oh . . . it was not itchy installing . . . like fibreglass would be. However it did tend to dry out my hands a little.


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## dalec (Oct 3, 2007)

Zuki,

Thanks for the additional info.

Dalec


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## douglas2cats (Mar 31, 2008)

I cut 2" styro on my TS with extremely good results when I was insulating a dog house project
http://lumberjocks.com/projects/9476
No ragged edges, melting, or any other problems and I was able to get snug friction fits on all the pieces. You could do 1/8" gooves with a standard saw blade. I was using a Forrest WWII. I'm not sure if you were trying to get 1/4" kerfs if you'd have the same luck trying to use a dado set with fewer teeth or not.


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## dalec (Oct 3, 2007)

Thing I am trying to avoid is that messy white stuff that clings to everything and scatters with the hint of a breeze. How bad was the residue from the cutting on the TS?

Dalec


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## ajosephg (Aug 25, 2008)

How flammable is today's styrofoam? Remember the night club fire of several years ago when exposed styrofoam caught fire and many people died.

If the mfg have not made it fire resistant then you should cover it with some material to protect it against ignition. I remember seeing demonstrations where a tiny flame would cause it to ignite and spread like lightning.


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## shimmy (Nov 8, 2008)

Here's how we use to do it out on the jobsite.

http://www.warehousebay.com/catalog/hot-knives-groove-tools-hot-knives-hot-groovers-blade-c-412_454_455.html?osCsid=c69b63f0010ac1f63a4c...
or
http://www.demandproducts.com/hotknife.php

Probably out of your price range but I thought maybe it would give you some ideas.


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## dalec (Oct 3, 2007)

Joe, good point. I don't plan on setting off fireworks in the garage, but I also don't want to make the garage any more flamable than it needs to be. Looks like more research!

Dalec


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## thom (Feb 16, 2008)

I cut mine on the table saw. Hook up your shop vac which should catch most of it.


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## dalec (Oct 3, 2007)

Shimmy, Hot knives? Pretty cool. I can't justify the cost for such limited use.

Dalec


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## northwoodsman (Feb 22, 2008)

I insulated my garage doors about 4 years ago using styrofoam and now almost everyone on my street has asked me to assist them. It is very easy! I purchased the blue 1/2" sheets that are 4' x 8'. I cut them on my table saw. I cut them a little larger than the opening so they fit under the flanges to hold them in place. I double these up so they are 1" thick. When installing them bow them a bit and they snap right into place. If you have a typical metal door, there will be areas that you will have to fill in with smaller scraps (you will see what I am talking about) on the right or left side of the door, and also in the middle if you have a 16' door. These smaller pieces have to go in first. I have had these in place for 4 years now using no adhesive and they have never moved at all. The key is a tight fit and "snapping" them in place. Use the dense foam panels, not the type where you can see each individual cell. The white stuff will break when snapping it into place. Granted I live in TX, but when it is 20º - 25º outside, it's still around 55º in my unheated garage. When I fire up the heater in the garage I can keep it at 70º by running the heater for a few minutes every hour. Also if you use adhesive, make sure you get the type made for this material otherwise it will melt it. You can easily insulate a 16' door in under an hour from start to finish.


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## dalec (Oct 3, 2007)

Thanks NorthWoodsMan.

Thanks for the information about your installation. I was looking at 1" thick sheets, but the 1/2" would be more flexible. Hmmm.

Dalec


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## Brad_Nailor (Jul 26, 2007)

The cleanest and easiest way to cut Styrofoam insulation is with a hot wire cutter. There are several inexpensive "craft" hot wire cutters some even use a heavier gage of wire that you can bend into any shape you want. Just make sure you are well ventilated and you have a fan blowing any fumes away from you. Do a Google search on "hot wire cutters" and you will find a ton of sites and blogs where people show you how to build homemade ones.

Joe the nightclub fire you are speaking of was the Station niteclub in RI, and the band ignited open cell foam the type that is used for sound dampening with their pyrotechnics.


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## pommy (Apr 17, 2008)

delac if your garage door is standard metal door then carpet tape would suffice as the adhesive propertys are very good i have used this method with a friend to great success

andy


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## 8iowa (Feb 7, 2008)

I have insulated my 16' wide metal garage door here in Gainesville. I purchased 4'x8' sheets of 1' thick foam insulation at Lowes. It is covered with a thin plastic sheet on both sides which helps a lot to limit the mumber of little shards of foam typical of uncovered stryofoam. I cut it with a sharp knife. Lowes also has an adhesive designed for foam insulation.

The whole job took about six sheets. On some of the door panels I had to cut two pieces and insert them separately. If there were any small gaps I filled them with white cauking. On the outside of the door I nailed up "seal stop" with the vinyl lip pressing against the closed door. This seals off the gaps on the doors sides and top. This has made a big difference. We've had several nights with temperatures at or a little below freezing, and a small 5100 BTU ceramic electric heater has been able to keep the shop above 60 degrees.


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## dalec (Oct 3, 2007)

Thanks everyone.

I am feeling better about using the 1" styrofoam sheet, now that I have gotten the info about the experience several of you have had using it. Hotwire cutters? Something else to consider. Don't expect to exposing the foam sheets to open flame, so it should be reasonably save to use.

Dalec


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## douglas2cats (Mar 31, 2008)

Dalec
I didn't catch your earlier question on the dust. I dont know about the white foam but the blue that I used wasn't very bad as far as dust mess on the TS. I wasn't very DC conscious when I was cutting it and probably only fired up the cyclone for about 50% of the cutting. Whatever mess I had left swept up pretty easily. There wasn't a problem with styro dust all over everything in the whole shop or floating in the air. It was pretty confined to within a few feet of the saw. The only other issue worth noting is that there's no weight to the stuff. so if you're at all lax about keeping it up against the fence it can kick it back pretty dramatically. But like I said, there's no weight to it, so it's not like kicking back a piece of wood. It's sort of like lofting a Nerf Frisbee. I had the shop door open and had one small piece lofted about 30 ft out the door.


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## TNWoodwright (Jan 19, 2009)

I used 1" foam laminated to 1/4 plywood. I laminated so the plywood stuck out on one side and was short on the other. Making a tounge and groove. I made them so the T&G was in the middle of the panel. Then put the top and bottom in and "snap" the tounge and groove in at the middle. Hope this make sense. Gives some protection to the door. you could use 1/4 OSB for one or both sides. ABout 5.00 a sheet.


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## cpt_hammer (Dec 18, 2007)

I just did this on mine garage door last month and I'm doing a friend's garage tonight. I wish I had actual pictures, but I haven't gotten around to it. The best thing I have found is that I didn't need an adhesive and my garage doors are helping, but I still have an attic and a wall to insulate.

Here's how I did it.

I used 2" thick styrofoam with a reflective siding from Lowes (click here )It has one side that is covered in the clear plastic and the other side is covered in a silver/reflective material. You want the silver side to be facing towards the inside of the garage. As it bounces heat back into the house.

Here is a drawing of a door similar to mine with 4 sections high with a center divider that created 8 sub-sections that I needed to fill with insulation. (I have no windows in my doors)










Notice the two Lips between the two sections. I measured my panels so that they would fit just barely inside those lips and I wouldn't have to use glue or worry about the panels moving. However my sub-sections were 50"x21". So I decided to cut 48"x21" and then a small 3"x21" piece that will fill the remaining 2" and I jointed them using a rabbit type joint (see diagram below).










The graphic below illustrates how I cut my panels out of the 4'x8' sheet of foam.

Each Sheet covers approximately ½ of a door.

Now the individual panels must be cut some more to make them fit into your garage door. Measure each door separately as mine were ¼" difference between widths of the sections. Luckily it was ¼" smaller so I just had to trim 1/4 " off of the panels. It would have left ¼" gap if they were larger. Each Section of the door was 50"x21" approximately.

Once I cut my sheet down into 48"x21" sections and 3" x21" end caps (to fill in the rest of the 50"). I cut a 1"x 1" grove (called rabbit joints) out of the back side of the 48"x21" panels (that is the white side). I then did the same to the 3"x21" panels on the front side (reflective side). (see diagram below) Together they should form a nice seal between the two pieces when joined. I then took the 48"x21" panels and cut 5 - 1" deep relief grooves in the white side (back side) of the foam in order to allow it bend so I can install into the garage door by bending the panels. This worked great as the panels fit tightly into the garage sections. I didn't have to cut the relief grooves into the small 3"x21" pieces because I put them in first and had room to angle them in.










This is how I did my doors. No glue was necessary and I only used a tape measure and a table saw and was able to complete 2 doors in about 2 hours.


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## cpt_hammer (Dec 18, 2007)

For some reason, I can't seem to view the pictures in my last posting? Can any of you see them?


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## dalec (Oct 3, 2007)

Thanks cpt_hammer for the very detailed explanation of your garage door insulation project. It was well thought out and it gave me several ideas, including the overlapping (rabbitting) the two pieces of insulation material for a tighter fit.

Nice illustrations. My door must be very similar in size and design to the illustration. I bought a 2' x 4' x 1" sheet of polystrene from Lowes yesterday to see if I could cut it clean enough and fit it tight enough to fit into one of the sections in the gararge door. I used a utility knife, so did not cut all the way through the 1" material. Scored it on the back side and popped it. I cut the sheet 20 3/8" and cut one relief cut in the center of the panel (need to improve on the relief cut and add a couple more) and used a wide putty knife to work the polystrene sheet inside the door panel section frame. It worked pretty well. Doesn't seem to need adhesive to hold it in place. And best of all, it would be a relatively inexpensive way to insulate my door.

I think I may give my table saw a try when I do the entire door. It will be much quicker, square and more even cuts.

Dalec


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