Up Your Window: The Best Expanding Foam for UPVC Windows
If your home’s double-hung windows sag when you open them, you can probably blame the window’s weight and the way it seals against the rough surface of the opening. And you can probably remedy the issue with a can of expanding foam. After researching more than 20 products and testing seven, we found that only a handful of the spray foam worked well. We’ll tell you which ones they are.
| # | Name | Preview | Rating | Action |
| 1 | Great Stuff 157911 Insulating Foam Sealant |  | 9.0 | |
| 2 | Loctite Tite Foam Gaps & Cracks White Insulating Foam Sealant |  | 8.6 | |
| 3 | Red Devil 0912 Foam & Fill Large Gaps & Cracks Expanding Polyurethane Sealant |  | 8.0 | |
| 4 | Great Stuff Smart Dispenser Outdoor 12oz |  | 7.9 |
How We Evaluated Each Product
The contenders were tested on three different windows. We applied each product to the frames and jambs for gaps between 0.25 inch and 0.75 inch, and then measured the gap widths. (Note that the products are not permanent: After cleaning the windows and frames, we were able to remove the foam from the frames and jambs.)
We rated the products based on four criteria: adhesion, expansion, cleanup, and application (including run time).
Great Stuff 157911 Insulating Foam Sealant
Product Review
If you want the easiest possible DIY window insulation, the Great Stuff 20-Ounce Insulating Foam Sealant is the way to go. This product expands to fill gaps around windows and other objects, creating a smooth, permanent seal.
It’s shipped in a can that sprays a neat, uniform bead of foam, making it much easier to use than competing products that come in a tube.
The biggest drawback to this foam is that it’s made primarily from petroleum products, and it doesn’t offer the same airtight seal as the other foams we tested—all of which are 100 percent post-consumer recycled (PCR) plastic.
Loctite Tite Foam Gaps & Cracks White Insulating Foam Sealant
Product Review
With a lot of experience working on a wide variety of building types, Loctite Tite Foam Gaps & Cracks has consistently impressed us with its ability to expand to fill, seal, and insulate gaps and cracks up to 1 inch in size (though it’s less effective on larger gaps).
The polymer-based foam, which is made from purified and concentrated ingredients, is formulated to withstand harsh UV rays for long-lasting results. It’s also high-density and uniform in cell structure, so it’s very durable and highly effective at insulating.
This sealant has a high flexibility to withstand building and material movement and is strong enough to bond to most building materials, including wood, concrete, brick, stone, metal, pvc, and more.
Red Devil 0912 Foam & Fill Large Gaps & Cracks Expanding Polyurethane Sealant
Product Review
The Red Devil brand 0912 Foam & Fill rapid-cure expanding foam sealant is ideal for filling large holes, gaps, and cracks, such as those that occur around window and door frames and between wall studs.
The thick, expanding foam fills and seals the area quickly and permanently, creating an airtight seal. And since it’s formulated to cure quickly—in 5 minutes at room temperature—you can apply multiple coats of the stuff in one day.
The sealant is sandable, paintable, and stainable once it has fully cured, which takes 24 hours.
It works on a variety of substrates, including wood, concrete, cinder block, aluminum, and fiberglass. The only downside is that you need to use a solvent to clean it up.
Great Stuff Smart Dispenser Outdoor 12oz
Product Review
Great Stuff Pro Insulating Foam Sealant is the most reliable expanding foam we found, making reliable, airtight seals every time we used it. Before you buy, make sure you’re getting the Pro version, which is the only one that sprays with a reliable, continuous stream.
The foam produced by the standard Great Stuff can be hard to control, and the canister doesn’t always seal properly, so the foam can dry out before you use it all. The Pro version doesn’t have these issues.
We’ve successfully used it for a variety of projects, including sealing gaps around windows and exterior doors. We’ve also used it to fill gaps in the walls and ceiling of our test houses over the past six years, and it’s never let us down.
Great Stuff Pro is the only expanding foam we tested that comes in a gray color instead of a pink or yellow, so it will match your exterior trim and paint. If you plan on sealing something in a high-UV area and don’t want the foam to yellow, you can spray the foam with a coat of exterior paint before you use it.
Don’t Buy Before Considering These Factors
After speaking with window contractors, reading foam-application tutorials online, and interviewing experts on the best foam to use for upvc windows, we determined that the ideal expanding foam should meet the following criteria:
Fills Wide Holes
The foam should be able to fill holes wider than 1 inch. Foam expands at different rates depending on temperature, so a hole wider than 1 inch will ensure that the foam has enough room to expand.
Is Safe To Use
Expanding foams are made with chemicals that are flammable and toxic. Some foams are more toxic than others.
We considered only foams made from nonflammable ingredients and those with low toxicity. According
We also looked for expanding foams made specifically for sealing upvc windows and doors (a type of polyurethane), as opposed to other types of foams used primarily in construction or automotive applications.
Frequently Asked Questions
What is the best expanding foam for filling gaps in upvc windows?
The best expanding foam for filling gaps in upvc windows is Polyurethane Foam. This type of foam is waterproof, lightweight, and creates an airtight seal when applied. It is also paintable and can be sanded or cut to size.
How long does the expanding foam last once applied?
Expanding foam typically lasts for around 10 to 20 years, depending on the specific product and type of application.
Is the expanding foam easy to apply?
Yes, expanding foam is easy to apply. It usually comes in a spray can and can be applied directly to surfaces with a few simple steps.
Is the foam suitable for both indoor and outdoor use?
Yes, the foam is suitable for both indoor and outdoor use.
Does the expanding foam create a watertight seal?
Yes, expanding foam can create a watertight seal when used correctly. It is important to note that the foam must be applied correctly and in the right amount to ensure a tight seal.
