Young handyman applying sealant to door with sealing gun in close-up view.

The Ultimate Guide to Caulking Interior Windows

If you’re like most people, you probably think of window caulking as something only necessary for exterior windows. However, did you know that window caulking can also be used on interior windows?

In this blog post, we will discuss the different types of window caulking that are available and explain how to use them properly. We’ll also provide some step-by-step instructions for those of you who want to try this project yourself!

Why do I need to caulk my interior windows?

Young handyman applying sealant to door with sealing gun in close-up view.
Image by tonodiaz on Freepik

Caulking interior windows is a simple but effective way to improve the energy efficiency of a home. Caulk prevents warm air from escaping in the winter, and cool air from leaking out in the summer, thus reducing energy consumption and saving money on utility bills.

By providing insulation around the frame, caulking also helps keep out drafts and reduces exterior noise when applied properly. Additionally, it can prevent moisture from entering and damaging the window frames or other areas of the home.

As such, caulking is an important step in creating an efficient “weather barrier” within a home that keeps out allergens too, leading to better indoor air quality and improved comfort for residents.

Indeed, regular use of caulk around all exposed seams of doors and windows should be a crucial part of any household’s maintenance schedule. Consider having our professional painters assist you with caulking your windows!

Types of Caulk

Acrylic latex caulk

Acrylic latex caulk is a popular product used in the construction, remodeling, and repair of various building elements. It is a relatively inexpensive and long-lasting solution with the ability to fill in small and large cracks, insulate against air and moisture, waterproof surfaces, and act as an adhesive.

Acrylic latex caulk is usually composed of a type of alkyd resin mixed with acrylic monomers as well as a pigment, stiffening agents, solvents, surfactants, rust inhibitors, and fungicides.

This flexible sealant provides elasticity which allows for some movement of parts without breaking the seal once cured. Acrylic latex caulk is ideal for indoor uses such as kitchen countertops or sinks if it is reinforced with silicone filler but should not be used on baths due to its potential mold growth problems.

It can also be used on more complicated projects outside the home like setting up window frames or corner joints in siding due to its easy application and protection against wearing out.

Siliconized Latex

Siliconized latex caulking is a type of caulk traditionally used to weatherproof and seal windows. Unlike other caulk varieties, siliconized latex typically comprises a water-based formula that is not only easy to tool but also extremely flexible, meaning it is well suited for use in highly expansive or contractive areas of the home like windows.

In addition, it’s made with silicone resins that help create an even stronger bond and allow for a more efficient waterproofing solution such as protecting window frames from moisture buildup or potential leaks.

Siliconized latex caulks can stand up to harsh outdoor elements including rain, sun exposure, and snow, making it ideal for those looking to install quality caulking in their homes.

Silicone Caulk

Silicone caulk is a type of sealant specifically designed for use around windows and other areas of a building requiring waterproofing.

It is made from a combination of silicone, plasticizer, and filler components that fill gaps and make sure there are no air drafts or moisture infiltration.

In addition to its waterproofing properties, silicone caulk also has an advantage over regular caulks in that it withholds its flexibility, making it suitable for both interior and exterior applications.

Furthermore, it holds up well over time in outdoor weather conditions due to being so flexible; its flexibility makes it resilient against extreme temperature fluctuations and UV rays.

Silicone caulk offers the added benefit of being paintable once it cures to the surface which makes it an ideal solution for preventing water damage while still achieving an aesthetically pleasing finish.

Polyurethane Caulk

Polyurethane caulk is a material commonly used for caulking windows and other surfaces. It is highly flexible and paintable, making it ideal for window trim as well as preventing air or water leaks.

Polyurethane caulk also adheres to many substrates such as brick, stucco, concrete, metals, and more. This type of caulk provides superior flexibility and resistance to shrinking and cracking over time, allowing contractors to apply the caulk on multiple surfaces without worrying about long-term durability.

When applied to windows, it forms a protective layer that helps prevent drafts of outside air from entering the home. Additionally, the sealing properties of this type of caulk help maintain temperature consistency both inside and outside a home by blocking unwanted temperatures outside while preserving the indoor climate.

Thus, polyurethane caulk is an essential component in providing energy savings while helping homeowners protect their homes from weather extremes.

Silane-modified polymers (SMPs)

Polyurethane caulk is a type of sealant specifically designed for windows. It is composed of polyurethane that provides a strong, flexible bond and can fill even the smallest gaps and holes to prevent air and water from seeping through the window frames.

The advantage of using polyurethane caulk versus other types of caulking is that it not only seals around the window frame but also holds up better over time as it is highly resistant to showers and storms.

Additionally, its durability means that it rarely needs to be redone or maintained regularly so once you have sealed your windows with it, you can enjoy the peace of mind of knowing they are protected from dust, wind, rain, and other outdoor elements.

Tools Needed

A carpenter holds glue while attaching a window.
Image by jcomp on Freepik

Caulking Gun

Caulking guns are hand-held applicators that make it easier to use caulking tubes on cracks or gaps in buildings and other structures.

Caulking guns are available at major home improvement stores like Home Depot and Lowe’s, and also from many online retailers specializing in home improvement supplies.

Modern designs of caulking guns allow users to achieve an easy and even flow of the sealant material, making applications faster and more accurate.

These tools come in a variety of features such as adjustable nozzles, smoother release buttons, powerful plunger springs, and ergonomic trigger position for user comfort when operating the gun.

Anyone looking for a caulking gun should be sure to compare these features across different products before making an informed decision on their purchase.

How to repair a broken window seal

A carpenter holds glue as they attach a window.
Image by jcomp on Freepik

Replacing a broken window seal can be an easy process if you know the steps and have the correct tools. The first step is to name the type of window that needs to be sealed- either casement or double-hung.

After this, measure the old seal and purchase a replacement that matches this size in length, width, and thickness. You will also need a measuring tape, utility knife, screwdriver, and caulking of your choice.

Begin by unscrewing the screws on the frame where the old seal is installed and gently removing them. Then clean away dirt or grime from the area with soapy water and dry it completely before installing the new window seal.

Apply a line of silicone caulk along each side of the window opening and then carefully lay the new seal into place. Finally, reinstall any screws removed in Step 1 and use painter’s tape to hold down any remaining open spaces until the sealant dries fully (usually 24 hours).


Interior caulking can be an effective way to add a tidy and professional touch to a space. The key to success is in being meticulous when applying it. Each step of the process, from cutting the tip of the tube at the right angle for an even bead of caulk, to using a damp rag to create an even line should be carried out carefully and by the instructions on the packaging.

When it’s all complete, any excess caulk should be wiped away with a dry cloth for a perfect finish. With this method, interior caulking can look great, effectively preserving overall aesthetics and preventing further damage as well.

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