How To Insulate Old Windows Without Replacing Them

You may have recently bought an old home or you've been thinking about how to make your home more efficient and sustainable. Insulating the windows is crucial to achieving this goal. But if you're wondering how you can do this without replacing the windows, you're in the right place. We've consulted the experts, and here's what they recommend.

To insulate old windows without replacing them, any of these methods will work:

  • Apply caulk
  • Install thermal curtains
  • Weatherstrip the windows
  • Install window inserts

Understanding heat flow is critical to understanding how insulation works and choosing the best insulation method for your old windows. Read further to find ways through which old windows contribute to heat loss and how you can address this. We will also tackle winterizing windows and when to replace the windows.

Old wooden house in the forest, How To Insulate Old Windows Without Replacing Them

How does heat loss occur?

wet window with water drops

It is prudent to understand how heat loss occurs through windows to determine the most efficient ways to combat this through insulation.

The old windows in your home can allow heat loss through different methods.

Air leakage allows indoor air to escape from the home and lets in outdoor air. Thus, the leakage creates a leeway for outdoor air to affect the temperature and comfort inside your home.

Heat loss also occurs through conduction. Hot air collides with the surface of the old window components, raising their temperature. This energy is then conducted via the solid material, where it meets the cold outdoor air and escapes. As the warm air comes into contact with the window components, it discharges heat, thus lowering the temperature.

While air gaps serve as thermal breaks to minimize conduction, they enable heat loss through convection if they are too large. In this case, heat energy emanates off one surface and cycles to another surface through the air. The heat is then lost through conduction.

Insulating old windows without replacing them

Condensation on an old window of a home

Addressing draft is one of the most cost-effective ways to improve comfort and efficiency in your home. For this reason, most of these low-tech fixes below to insulate your old windows focus on minimizing or eliminating air leakage.

Apply caulk

Latin American building contractor installing a window and applying silicone sealant - housing development

Caulk is suitable for sealing gaps, cracks, and joints that let in cold air. Use caulk to seal gaps that are not more than a quarter of an inch. Caulking between the interior window trim and the wall keeps draft out.

While you can also apply caulk on the outer perimeter of the window, take care to ensure that you do not clog weep holes or caulk the moveable components of the window. Weep holes are situated at the bottom of the window sill and function as drains for the window. Where weep holes are clogged, moisture may seep into the wooden window sill, causing it to rot.

Ensure that you buy caulk that is clearly labeled for windows. Additionally, remove any old caulk before applying a fresh layer to create a proper seal that will last long. Getting rid of old caulk is crucial since fresh caulk does not stick on old caulk.

This silicone sealant is 100% waterproof. Additionally, it won't yellow, shrink or crack. Click here to see the product on Amazon.

Install thermal curtains

Thermal curtains raise the insulation level of your windows by keeping cold air from entering the room. Instead, the cold air is trapped between the curtain and the window. These curtains help you save energy by minimizing air leakage.

Thermal curtains are made of double or triple layers of fabric, especially suited to resist moisture and bar cold air from infiltrating the room. To ensure maximum efficiency, choose thermal curtains wide enough to cover the windows sufficiently and long enough to extend to the floor.

Good quality thermal curtains also dampen the noise. Moreover, dark-colored curtains block all the sunlight, creating a suitable environment to sleep in.

This set of blackout curtains is thermal-insulated, enabling you to regulate the temperature in your house. Click here to see the product on Amazon.


Hands Applying Weather Seal Caulk to Window Frame

Weatherstripping minimizes draft, reducing energy loss through windows. It is easy to apply and remove. The material used for weatherstripping will depend on the type of window installed. Note that choosing low-grade materials for weatherstripping or installing them poorly will result in dismal insulation.

Remove any worn-out weatherstripping before installing a fresh layer. Additionally, cut the weatherstripping material to fit the length of the window frame. However, do not layer the stripping too thick to ensure that you can easily open or close the window while the weatherstripping is still in place.

This weatherproofing tape is moisture resistant. See it on Amazon.

Install window inserts

Window inserts are fitted on the inner side of existing windows. They provide insulation by creating an air pocket between themselves and the window, decreasing energy loss through radiation. Some inserts are secured in place using compression tubings. These tubings create a tight seal around the window frame without damaging the window or the frame.

Most window inserts are unnoticeable, hence ideal for historic homes. But since they are custom-measured, they allow you to preserve the beauty of your windows. Your home will also benefit from UV protection and light blocking when you use window inserts.

How to winterize windows

man caulking window during the day

Winter brings new challenges to your home. Thus, prepare accordingly to ensure comfort and efficiency throughout the cold season.

Winterizing your windows keeps your home warm and improves energy efficiency. It entails putting in place measures to ensure that the cold outdoor winter air does not permeate your home. You can do so by eliminating the gaps between the window and your walls. You can achieve this by caulking, weatherstripping, or adding a window covering.

You can also use an interior window insulation kit to winterize your windows. The kit contains a heat-shrink plastic. It eliminates any air infiltration when installed over the window, boosting your window's R-value. Insulation improves as a result.

A major drawback when winterizing your windows using the insulation kit is that removing the sticky tape at the end of the season can ruin the paint or varnish on the trim. Additionally, the quick fix is not environmentally friendly since it is a temporary solution.

How do you know when it is time to replace old windows?

Renovation work in an old house and replacing windows, building energy efficiency

Windows provide a home with ventilation, enhance aesthetics, provide lighting, keep your home safe, and reduce noise. Considering all the benefits of great windows, replacing them is a big decision. You should carefully consider whether it is the right move before making the decision.

These signs will help you determine whether it is time to change your windows:

Drafty room

Although winterizing your windows is meant to keep the cold outdoor air outside your home, it can be a good indicator of the condition of your windows. If your home is still drafty even after winterizing it, it may be time to install replacement windows.

High energy bills

Insulating your windows should result in lower energy bills. Nonetheless, if you notice that your heating and cooling costs do not reduce, installing new windows may be your best bet towards achieving energy efficiency and subsequently lowering your energy bills.

Difficult to operate

Typically, operating windows should be quick and easy. However, these windows are subject to wear and tear. Tiny grooves and divots form, causing your window to get stuck. When this happens, it may be time to replace the windows.

Foggy windows

If you notice that your double-paned or triple-paned windows have a fog-like appearance, this may indicate that the air trap is leaking. Fog may also be an indication that condensation is trapped inside the windows. As such, your windows are not as efficient as required, which should mean they need replacement.

Damaged window frame

A damaged window frame compromises the insulation's efficiency and the efficiency of the HVAC system. The cracks can also create a passageway for insects into your home.

Furthermore, moisture damages wooden windowsills, causing the sills to rot. If you notice that the sill is soft to touch or has cracks, it would be wise to replace the window rather than repair the damaged frame.

Final Thoughts

old wooden window with winter frost

Old windows are an essential feature of the character of a building. Thus, although lowering your energy costs and creating a comfortable space to live in would be quite welcome, you might not be overly enthusiastic about replacing these windows.

Conducting an energy audit will enable you to determine where the heat loss occurs. You can then develop an effective way of addressing the issue.

You can easily do low-tech fixes yourself to insulate old windows, eliminating the need to replace them. However, considering that the average lifespan of residential windows is 15-30 years, you will eventually need to replace those old windows. Choose windows that blend with your old house's architecture and character when the time comes.

Check out these other posts to learn more about insulating windows:

How To Insulate Very Large Windows [For Summer And Winter]

How To Insulate Glass Windows [Including Leaded Glass]

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