<h1>Coincidentally, I just got an email from Sailrite on this subject. I hope it'll get posted by our moderators even tho it might be construed as advertising.* I have no interest in Sailrite except as an info source - their mini-videos are often helpful.</h1><h1>*</h1><h1>Boat Window Insulation</h1><h3>Written by Dan Smith, Sailrite employee</h3>
A common problem for anyone living aboard a boat is keeping the heat out during the summer and keeping the heat in during the winter. The problem grows exponentially with larger windows, like those found on trawlers and houseboats that seem to have a built-in convection draft that sucks air right out of the boat.
As a live aboard myself, I've observed several different methods for insulating a window over the years, but none seemed to offer an optimal solution. Standard curtains or drapes provide some relief but are not sufficient on really cold or windy days. Thin cushions, made from ½" Ensolite foam and sized to fit into the windows, cut down the draft but kill any light coming into the boat and require drilling holes in the interior of the boat for the mechanical fasteners needed to hold cushions in place.
While helping a fellow live aboard and Sailrite customer, I came up with an effective (and creative!) solution using sheets of random fiber expanded foam packing material (found at any post office). This translucent foam material is a great insulator and is only about 1/16"1/8" thick allowing for more light and less bulk.
Make Your Own Snap-On Window Curtain Panel Video
Use the foam material as a liner between (or behind) panels of Sunbrella Shadow
(preferably light colors like Snow or Sand). Covering the panels with Sunbrella on just one side will let more light through, but the window will not have as finished a look when viewed from the outside. Fold the outer edges over twice and sew to create a rubbed seam or bind with a 1" premade binding to finish the edges.
Hang the window panels with the new adhesive-backed YKK SNADs
. A SNAD is a low profile nylon molded male or female snap held in place by a high tech 3M adhesive. Install a button snap in all four corners of each panel. Then attach a male stud SNAD to each button. Pull the paper backing off the SNADs and adhere directly to the glass, smooth fiberglass, or varnished wood surface.
The result is an attractive window cover that provides both insulation and privacy while still letting in quite a bit of light. Your neighbors will be impressed and probably want to know where you got them!
A summer alternative to the foam material is Sailrite's Thermozite
material. Thermozite is a very good insulator and when installed with the shiny side facing the window also reflects sunlight to keep the heat out. The obvious drawback is that Thermozite is opaque and will block all light. Use SNADs and female snaps as described above to hold the panels in place.
Thermozite Alternative Window Panel Video
If I were refurbishing my boat, I would create window covers using Sunbrella Shadow and create ceiling panels with Thermozite insulation. (Boater lingo is a bit funny as "ceiling" panels refer to the vertical sides on the inside of the hull and "overhead" to the horizontal surface above your head.) Adding Thermozite Insulation to the inside of the hull will help keep the heat in or out when oftentimes the only thing between you and the elements is less than ½" of fiberglass.