[Greenbuilding] R20 window insulation?

[Lawrence Lile]

I've been using Rmax interior insulating shutters for quite a while.  Mine are pretty simple - some of them just force fit into the window frame, I paint the inside (gotta prime them first - or the Rmax logo shines through) and paint the edges after duct taping them with white duct tape.  Some of them have magnetic seals, some not.  About as red-neck hillbilly a solution as you can come up with. 

Have a lot of trouble with magnetic strip seals.  They can pull off of the Rmax.  They don't adhere to a painted wall worth a darn, and I end up nailing them on every 8".  Strip Magnets are also ugly. I probably won't use them again if I build another shutter.  I took some of them off and converted those shutters to force-fit. 

The slickest insulating shutters I have use button magnets.  I carefully core out a hole in the back of the shutter, and set a powerful button magnet just below the surface of the foil.  Then I stick it onto some metal to hold it, and squirt some caulk behind it to hold it in place, patching the hole finally with some wallboard paste.  Paint the back the same color as the wall.  Magnets are invisible. These stick to the wall because there is a metal bead in the sheetrock return around my windows.  Won't work with wooden trim or plastic sheetrock edges.  But they stay up by themselves invisibly and don't warp as bad as some of the other methods. You could also make these by drilling a hole all the way through and sticking duct tape on the window side, with a magnet inside the foam against the tape.

Some of them have two layers of Rmax, one that fits outside the window frame, and one that force fits inside the window frame.  These warp less than a single sheet, and seal up better.  They are bulkier and a little heavy on a large window.

None of these seal very well on the edges.  The force fit and two-layer ones have the best seal.  I know that insulating shutters are less effective if they don't seal on the edges.  I do get quite a bit of condensation, even window frost, on the worst-fitting ones.  The condensation isn't good for the wood on my windows. Oh well. I have never found a good edge sealing material that holds up.  Duct tape, folded into a flap, actually works pretty well with a tight-fitting foam insert. 

All of my shutters are either 3/4" or 1.5" thick, making them about R4 to R8.  There are diminishing returns for every extra layer of insulation you add, and I figure this is a helluva lot better than R2 windows.  Fixing the leaks around the edges would do much more good than adding more layers. Thicker ones are bulky and awkward if the windows are large. Assembly with a 6" air gap (R2.7?) is probably R12.  

Some of them have a little plastic window, made of that shrink-to-fit plastic and double sided tape.  I have one window that the cat looks through when he wants in the sliding glass door, I have another one that I can watch the back yard bird feeder through.  I highly recommend using some little windows, so you can see who is knocking on the door or watch the bird feeder.  I leave all these shutters up on cloudy days, and little windows make the place less cave-like. 

It takes 30 seconds to take down all the shutters in the living room.  All the shutters on the North and West walls stay up all winter. Every time I get grumpy about the chore of taking them down I think "Just thirty seconds".  


--Lawrence Lile, PE, LEED AP, CEM


> -----Original Message-----
> From: greenbuilding-bounces at lists.bioenergylists.org [mailto:greenbuilding-
> bounces at lists.bioenergylists.org] On Behalf Of Bob Waldrop
> Sent: Thursday, January 06, 2011 10:47 PM
> To: Environmentally-preferable design, construction, building elements
> Subject: Re: [Greenbuilding] R20 window insulation?
> 
> Yes, I apologize if this wasn't clear to start with.  I usually refer to
> them as insulated interior window shutters.
> 
> Bob Waldrop
> 
> ----- Original Message -----
> From: "Gennaro Brooks-Church" Wait a minute, those are not R20 windows.
> Those are R20 window covers!
> 
> Gennaro Brooks-Church
> 
> Cell: 1 347 244 3016 USA
> www.EcoBrooklyn.com
> 22 2nd St; Brooklyn, NY 11231
> 
> 
> 
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