DIY Attic Insulation: Block Light and Heat on a Budget

A poorly insulated attic causes significant energy losses in heating in winter, and during the warmer months, the temperature inside increases significantly as the sun shines directly into the room, making it more difficult to cool it down.

Considering that almost a third of a home's heat escapes through the roof and another 20% is lost through windows, it is necessary to find practical solutions to optimize insulation in these rooms.

Furthermore, many blinds used on roof windows do not completely block the sun, causing light to disrupt sleep and allowing heat to enter more easily in summer.

In this instructable, we will make our own custom-made, foldable and insulating sunshade for roof windows, inexpensively and with no need of complex installation or window renovations. Although this design is intended for roof windows, it can also be applied to camper vehicles or any other type of window.

To get started, we’ll need the following materials:

1. Corrugated cardboard (it must be corrugated because the inner flutes create small air chambers that act as insulation)
2. 4 suction cups (at least)
3. Reflective plastic (such as a thermal blanket or metallic gift wrap)
4. Black garbage bag (or another lightweight black plastic)

Both coverings should be plastic to prevent damage to the cardboard from moisture caused by condensation on the window.

And the following tools:

1. Measuring tape
2. Ruler and pencil
3. Scissors
4. Box cutter
5. Cutting mat
6. A cylindrical tool (like a chopstick) to help pierce holes
7. Adhesive for paper and cardboard (in this example, hot glue was used, but you can use whatever is most convenient for you)

Measure the width and height of the window using a measuring tape and write down the dimensions.

Draw the measurements on the cardboard and divide the width into equal parts. We divided this one into 6 slats for storage convenience. Draw the vertical lines parallel to the corrugation for better structure.

Using a cutter and cutting mat, carefully cut out each slat of the reflector.

Mark the points where suction cups will be placed. If you think that the cardboard weight, or the size of your windows will require more support, add more suction cups. In this example, two on each end of the first and last slat, at the same level, will be enough.

Use the cutter and a cylindrical tool to create holes where the suction cups will go. Enlarge the holes until the suction pull tab fits.

Cut and stretch a black plastic bag to cover the entire surface. Ensure that two of the slats with the suction cup points are at the ends.

Attach the black plastic to the slats using adhesive. Leave alternating gaps between slats to allow folding. Continue gluing, alternating the gaps: space–no space–space, etc., to finish attaching the black plastic.

The black side of the sunshade should face into the room during the summer months to avoid adding heat indoors, and face outward in winter to absorb heat from outside.

Re-pierce the holes for the suction cups so you don't lose the exact placement on the cardboard. Simply tear the plastic in the same way you did the cardboard.

Turn the cardboard over, fold the black plastic over the edges, and glue the reflective plastic on the other side. Alternate the spacing opposite to the black side (no space where there was space and vice versa). Re-pierce the holes.

The reflective side should face outward during the hot months to reflect sunlight, and face inward in winter to retain heat generated by the heating.

Make sure the sunshade folds properly and that the suction cups can be removed and reattached from either side of the cardboard.

Attach the suction cups to the glass and unfold the cardboard fully across the window. Adjust for desired light.

Detach the suction cups and fold the sunshade accordion-style for storage.