Windows have lower resistance to heat flow than walls. While double-pane glass windows offer significant improvement over its single-pane alternative, the window remains the weakest point of your home’s insulation. Although windows are necessary to allow natural light to enter the dwelling during the short winter days, they contribute significantly to the loss of heat during the frosty winter nights. This instructable will share our experience in building removable window insulation that increased the comfort and reduced the energy usage of our household during the winter nights.

Note:

Conversions between metric and imperial units in this instructable are approximate and within the acceptable variances for the project.

Supplies

Materials

Reflective bubble insulation

It basically consists of thin bubble wrap with silver reflective layers on both sides. It is also known under the names "Double Reflective Insulation Radiant Barrier" and " Radiator Reflector Insulation". It can be sourced from Amazon or a local hardware store.

PVC tablecloth (optional)

Just a basic PVC tablecloth. It is function is purely aesthetic. It can be sourced from Amazon or a local home goods store.

Sticky back velcro strips

Strips of velcro having double sided adhesive. Can be found in long rolls or pre-cut. Some of the variations are known as "Picture Hanging Strips". It can be sourced from Amazon or the hardware section in one of the large supermarket chains.

Clear tape

Just a roll of clear tape. 25mm (1") wide is sufficient, although wider can be used as well. It needs to be of good quality in order to work well. I used Sellotape brand. Use one of the leading brands available where you live.

Tools

Tape measure

Scissors

Ruler

I used T-square which makes it easier to determine 90-degree angles, but anything straight and sufficiently long should be fine.

Marker

Just a basic marker. Using pencil or a pen is not advisable as it may pierce the insulation.

Step 1: Measure the Window

Measure the window width and height. Take the measurements as close to the window as possible as this is where the insulation panel will be installed.

Step 2: Join Multiple Pieces of Reflective Bubble Insulation

Reflective bubble insulation typically comes in sizes that are too small to cover most windows and joining multiple pieces will likely be required. If the sheet of reflective bubble insulation is larger than the window size, you can skip this step.

Use the clear tape to join multiple pieces together so that they are larger than the window size. Tape both sides of the seam between the pieces. Try not to leave any gap between in the seams.

Step 3: Cut the Reflective Bubble Insulation Sheet to Size.

Use the ruler, tape measure and marker to draw the cutting line for the scissors.

Aim to cut it about 5mm (¼”) smaller than the window size in both, width and height.

Use the scissors to cut the reflective bubble insulation.

Take the cut sheet to the window and check the fit, cut additionally if necessary. The insulation needs to fit freely within the window but gaps should be kept as small as possible to reduce the exposed surface.

Step 4: Add the PVC Tablecloth to the Reflective Bubble Insulation (Optional)

The purpose of the PVC tablecloth is to prevent drawing unnecessary attention to the property as the shiny surface of the reflective bubble insulation looks unusual through the window. If this is not a concern for you, feel free to skip this step.

Lay the PVC table cloth on a flat surface with the back side facing up.

Place the reflective bubble insulation on top of it.

Mark and cut with the scissors the PVC tablecloth leaving 25mm (1”) on each side around the reflective radiator foil.

Fold the extra PVC tablecloth around and tape it to the reflective bubble insulation. You can over lay the corners.

Step 5: Stick the Insulation Panel to the Window

In case you use long strips of velcro, cut them in short pieces, about 35mm (1 1/2") long.

Peel the film from one side of the velcro strips and stick them evenly to the window frame.

Peel the film from the other side of the velcro strips to expose the adhesive.

Align the insulation sheet and press it against the velcro strips.

Step 6: Usage

To remove the insulation, carefully split the velcro strips.

To install the insulation, align the velcro strip halves located on the insulation panel with the ones located on the window and apply gentle pressure.

It might be beneficial to mark one of the corners to make sure the insulation is installed in the correct orientation to ensure alignment between the two parts of the velcro strip. Also, further numbering the insulation panels will assist you in identifying which panel is for which window, reducing the probability of attempting to fit the wrong panel.