Big windows in a boat are wonderful for providing views but can really heat up the inside. Regular shades work most of the year, but better window shades can lower interior temps by 10°. Just 5 minutes and less than $20!

Better Window Covers

If you’re in the tropics or near-tropics for the summer, you know that sunlight streaming through every window — hatch, port, or whatever you call it — just adds to the heat inside the boat.

Catamarans, trawlers and some newer monohulls are the worst, with large non-opening windows. They offer gorgeous views from inside the boat, but can raise inside temperatures considerably.

Big windows in a boat are wonderful for providing views but can really heat up the inside. Regular shades work most of the year, but better window shades can lower interior temps by 10°. Just 5 minutes and less than $20!

And so, the first thing most boat owners do is to make (or have made) snap-on exterior shade panels with a fabric such as Phifertex or Phifertex Plus. Both of these block a fair amount of the light (70-90%) but still let you see out a bit. Our boat came with one for the saloon windshield, and I made another for the large window in our cabin.

Big windows in a boat are wonderful for providing views but can really heat up the inside. Regular shades work most of the year, but better window shades can lower interior temps by 10°. Just 5 minutes and less than $20!

They snap on, which is helpful for the one that the helm looks through (we take it off before getting underway — it’s part of our “Before Moving Boat” checklist), and they do a great job nine months of the year.

But, we’ve learned, they are woefully inadequate during the summer. Enough sunlight comes through that the window gets uncomfortably hot to touch!

We looked at all sorts of possible solutions and ended up going for the 5-minute, less than $20 solution. We bought a roll of Reflectix (bubble wrap with foil on both faces) and cut it to the size of the windows and slid it under the snap-on shades. I simply cut out little places where the snaps are so that the Reflectix can be the full size of the window.

Big windows in a boat are wonderful for providing views but can really heat up the inside. Regular shades work most of the year, but better window shades can lower interior temps by 10°. Just 5 minutes and less than $20!

My technique was simple — I cut the pieces roughly to size, put them in place (on our boat, it was easiest to set them against the bottom snaps), made the cutouts for the snaps on that side (on ours, the bottom), slid the Reflectix into its “final” spot, trimmed up the other sides and cut the holes for the rest of the snaps, then snapped the fabric covers back into place. Two done in about 5 minutes.

It has made a big difference in the temperature inside the boat. Temps inside the boat used to be about 10 degrees (Fahrenheit) hotter than outside “in the shade” temperatures; now they are about the same. 90° in the boat is a lot more tolerable than 100º!

We got the idea from another boat that was going on the hard for hurricane season, but it works just as well if you’re living on the boat.

NOTE: Putting the Reflectix on the inside of the boat is a bad idea we’ve learned — the heat will build up between the window and the Reflectix and can damage the window. Putting it on the outside, on the other hand, helps to protect the window.

When we get ready to get underway, we always remove the snap-on shade over the windshield anyway and put it back in place once we’re anchored or at a dock. With the Reflectix in place, we simply roll the Reflectix up with the shade to get underway and put them on together at the end of the trip. It takes no more time.

We had seen various ways to make pockets in the shade cloths for the Reflectix or to otherwise attach the Reflectix either to the boat or the shade. We have found it totally unnecessary.

Big windows in a boat are wonderful for providing views but can really heat up the inside. Regular shades work most of the year, but better window shades can lower interior temps by 10°. Just 5 minutes and less than $20!

Yes, with the Reflectix in place we lose the view and so don’t use it during the cooler months. The pieces are easy to store under a mattress during the winter and we’ve found that even in tropical sun and rain, they last two to three years. They didn’t disintegrate; the foil just slowly wore away so that light started coming through. Exact longevity will depend on how much of the year you use them and how intense the sun and rain are.

A couple weeks ago I had to replace one and walked over to the Home Depot in Marathon, Florida (it’s a couple blocks from Boot Key Harbor, making it very convenient for cruisers). I figured with all the part-year residents leaving homes and boats here, Reflectix would be a popular item. Discovered that they don’t carry it or anything similar in stock at this store (only their larger stores do). Turns out that no local store carries it. Okay, off to Amazon (seems to me that there’s a business opportunity here for a local entrepreneur):

Reflectix comes in a bunch of different sizes, so you’ll have to do some rough measuring to figure out what width and length roll will work best for you. It also comes in “tabbed” for stapling in home construction; this generally isn’t needed for making sun shades but can easily be cut off if that’s all you can get.

P.S. If you have large “glass” hatches, look at Outland Hatch Covers to insulate (and also protect) them. Read my post here.

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12 Comments
  • Claire Ford
    Posted at 12 June 2017 Reply

    Great article. Since we’ll be moving the boat to Texas from Kentucky in a few months, I’ll be looking into doing this. In Texas, anything that keeps it cooler is welcomed.

  • Jim Taylor
    Posted at 13 June 2017 Reply

    I have a 3′ x 4′ plexiglass roof on our pilot house and have used this material with a layer inside and outside. Know of an coating or film I could use on the outside to reflect sun, rays, heat but still see through?

    • Carolyn Shearlock
      Posted at 13 June 2017 Reply

      Use automotive/limo window tint film — the darker the better. You can get it at almost any auto parts store and also on Amazon: http://amzn.to/2thV0K9

      • Eve
        Posted at 15 June 2017 Reply

        Be very careful about which window film you buy. Most labeled UV are not tested or lose their UV abilities in a very short time. The Skin Cancer Foundation recommends only 2 brands (3M & Llumar). I have had both on my vehicles, as I tend to get benign skin cancers easily. 3M Crystalline and 3M Color Safe are the most durable in my opinion (I had a bad experience with scratching on Llumar Air 80).

        The 3M tints even come in clear and block 99.9% of UV-A and UV-B rays, PLUS…. it rejects up to 62% of solar energy and up to 97% of heat-producing infrared rays. It makes a HUGE difference in my car (I live in a hot part of California). I have the lightest tint on my windshield and medium on my side windows. Even on 100 degree days, you can get in the car and it’s not very warm at all.

  • Bob Menches
    Posted at 14 June 2017 Reply

    If you can’t find reflectix and have an autoparts or Walmart near, get a windshield shade made the same material. That’s what we did before we knew reflectix existed.

  • Thomas Conover s/v Double Life
    Posted at 14 June 2017 Reply

    I believe I had Home Depot in Marathon ship a roll into their store free shipping and then just picked it up at the store in a few days. Seems like they would stock it but ordering was simple.

    • Carolyn Shearlock
      Posted at 14 June 2017 Reply

      At the time we needed it, they said 10 days for delivery. Amazon was two. And it was HOT.

    • Carolyn Shearlock
      Posted at 14 June 2017 Reply

      At the time we needed it, they said it would be 10 days for delivery. Amazon was two. And it was HOT. Guess who won?

  • Cheryl Geeting
    Posted at 20 June 2017 Reply

    Sounds great, but does the Reflectix damage the plastic ports with its heat? I thought I read somewhere on your site about That? We definitely need something here in Louisiana!

    • Carolyn Shearlock
      Posted at 20 June 2017 Reply

      If you put it on the OUTSIDE it does not. It protects the plastic from the heat.

  • Carey Mitchell
    Posted at 21 June 2017 Reply

    I covered every inch of the interior of our refrigerator and freezer (like wallpaper) with Reflectix and boy did it make a difference. I used the accompanying foil tape to hold it in place. Not only does our top-loading fridge lid not sweat on the outside in high humidity, but we also save a lot of compressor use and thus battery power. We keep our boat on a mooring in Maryland in the summer and never have to turn off the fridge while we are away.

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