Sun Covers for Windows

By Carolyn Shearlock © 2014 • all rights reserved

Easy DIY project to keep your boat cool

Every time we’ve been aboard a catamaran, Dave and I have remarked about how light and bright it is inside. But last January, aboard Beagle Knot (they’ve just started officially offering charters — check them out) we discovered the downside to this, as well as a simple and ingenious solution.

You see, all the panoramic (and mostly non-opening) windows aboard Beagle Knot are fine while the sun is high in the sky. But by mid-afternoon the sun is pouring through those windows on one side of the boat and it’s getting HOT inside!

Windows windows windows

LaDonna got some auto windshield reflectors and cut them to size for the windows and simply puts the ones in that are needed on a given day. She uses just a bit of masking tape on each one — since they’re only up for a few hours, it comes off easily. You can see in the top photo how she labelled each one for where it goes — it literally takes her about a minute to put them up!

If they’re leaving the boat for any amount of time — say snorkeling, walking the beach or a shore excursion — they put all the window covers in so that even if the boat swings at anchor, the inside will be shaded.

They also have pieces on the inside of the hatches in the cabins — these are usually open when at anchor and only closed underway or if it’s raining, so it doesn’t interfere with light in the cabin but significantly cuts the heat build-up when they’re underway. Should there be an extended rainy period when they want the hatches closed but also want the light, it only takes a second to remove them.


Reflectix-thumbWhen we bought Barefoot Gal and immediately prepped her for summer storage in the blazing Florida sun, we did a slight variation on LaDonna’s idea. We bought rolls of Reflectix, which are basically the material that the auto windshield shades are made from and cheaper than the shades (it can be hard to find outside the US, hence using windshield shades). I’ve written before about using Reflectix to add insulation to your refrigerator or cooler — see that article here.

Reflectix is easy to cut and shape as necessary — it’s bubble wrap with foil on both sides. I simply taped a piece roughly in place, then used a felt pen to draw the shape of the window. I took the piece down and just cut along my lines and got quite a good fit.

I didn’t want to use masking tape as I worried that it’d be hard to get off after six months. Instead, I used Command Strips for posters. The poster strips are much cheaper than the heavier-duty picture hanging strips, and provide plenty of hold as the Reflectix is extremely light weight. So far, our boat-watcher says they’re holding just fine (we were worried with the heat) and none of our pieces have fallen down.

UPDATE: Don’t use Command Strips. They leave a nasty residue on the windows in the sun.

NOTE though, that the command strips aren’t suitable if you’re using the windows covers on an as-needed basis.

Reflectix covers for all windows

Both Reflectix and Command Strips are sold at many home improvement stores. In Fort Myers, where we were, Home Depot didn’t carry it in the store, but Lowe’s did. If you can’t find it near you — or just prefer the convenience of having it delivered to your door or the marina office — both are available on Amazon:

Wondering how much to get? To do our entire boat (Gemini 34′ catamaran) I used one roll of Reflectix that was 18″ wide and 25′ long and one that was 24″ wide and 25′ long and had a little left over.

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  1. Yes! We do this, too. I’ve found if you cut them a1/2 inch bigger than the window opening, they’ll stay put without tape. (On our boat, at least.) To take function into fashion, I sewed a cool fabric to the inside of the panels using a zig zag stitch.

  2. Be careful. This works great in the side windows, but on our Gemini, after a couple of years, two of the horizontal hatches had bowed lenses, which then leaked. We suspect it may have been heat build up between the aluminum and the lens due to reflection. We’ve since made outside covers (phifertex plus in a light color) which work beautifully.

    • Eww, we’ve had them in our hatches all summer. Hope that didn’t happen on our Gem — at least our boat watcher hasn’t said anything about a leak. I’m hoping. Thanks for the warning!

  3. We’ve done this too. Helpful to keep out heat and cold! Just made them a bit larger than the port opening and tuck them in. They stay nicely.

  4. Jennifer Spires says:

    I have a Gemini, too. I’m worried about the sun shining through the glass, reflecting off the reflectix and back through the glass. Is that going to cause twice the damage to the plexiglass? Right now I have a piece of outdoor fabric that I put buttonholes in and hang it on the glass with suction cup hooks from a fabric store. I can easily take it down while we’re underway and later put it back up. The thickness of the reflectix would do a better job of keeping the cabin cooler, though.

    • I hadn’t thought of it being a problem and have seen lots of stored boats with the Reflectix in the hatches. But another commenter did mention they’d had a problem with it, so I’m just not sure.

  5. Mili Cook great idea! May I add your pic to Pinterest? We don’t have a boat yet, but I’m pinning an archive of info for later use.

  6. This is also a good addition over the top of the icebox (below the lid). Our reefer/freezer power consumption dropped by 15%

  7. We have done this also. I did put the little round Velcro on it to hold in place. We have ours up all day if in the south. Helps greatly on the heat

  8. I have made window covers like that for all three of my boats. The edges can even be sewn with an overlock or zigzag edge on a regular sewing machine!

  9. Toni Borrett says:

    Great article! How do you keep the boat ventilated when locked up for months? Any advice? Thanks

  10. If you are worrried about the sun heating up the inside,i have found if you put the auto sunshades on the outside of the window it keeps the heat out better and my car stays cooler.

  11. I have a 380 Catalina and I have a product on my hatches made by Outland Rigid Hatch Covers and it sits on top of your hatch and reflects, protects the lenses and does a tremendous job on insulating the heat from entering the boat. They can also make them for non-opening cabin windows. Actually they can make them for most any window or hatch area. Check them out on their website at They have videos on there for you to see the process and how they work. I have found that this is an inexpensive way of protecting your investment.

  12. Cathy Waldron says:

    Our boat came with a set of window covers made from car sunshades and to hold them in place they cut a small hole in each end and inserted suction cups and on place of the hook they have small cable ties to stop them slipping through the holes. We live on our yacht, a 14.8m Radford in tropical Australia, and I have remade them whenever they get a bit saggy or crumpled. As they are easy to remove and replace we can allow light in and keep the hot sun out on different sides of the boat depending on the time of day, or angle of the boat when we are anchored. They also allow the windows to be opened, although during the hottest part of the year (now) we have an air conditioner in one of the hatches, so keep the boat shut up as much as possible. As we have 16 windows it is a cheap option and works well for us.

    • Cathy, You might want to look at the covers from Outland Rigid Hatch Covers, they go on the outside of the hatches and keep the glass from crazing from the sun. They a very good installation factor when you are trying to keep it as cool as possible in the hot summer months. They have worked wonders for us.

  13. If you are having trouble getting sticky residue off glass or plastic surface, use eucalyptus oil. Put the oil onto the offending material, leave it to do its work for 5-10 mins and than wipe off.

  14. StarWish246 says:

    Perhaps, since warm air rises, this might help. Get a paper hole puncher (or use a drill) and make holes along the bottom of the covering. This might pull cooler air (cool air goes down) between the plexiglass and the covering. Sort of like leaving a window open slightly to balance the heat / cool.
    I do know that the color White reflects heat, too. You could spray paint the foil on the side that faces outward of the window covering with white paint. Flat white may be less problematic that the shiny foil.

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