Toasty Feet are insulated with Aerogel, which was developed by Aspen Aerogels for NASA, and is claimed to have the highest thermal insulation value of any solid material available. Their website claims an R-Value per inch for Aerogel of about 12, compared to about 4 for Thinsulate and 2.5 for fiberglass. The Toasty Feet Insole reduces conductive heat loss from the bottom of the foot. So, how do these insoles insulate when you are standing on them?
Aerogel is a silicon-based solid with a porous, sponge-like structure in which 99.8% of the volume is empty space. It’s 1000 times less dense than glass, which is another silicon-based solid. Aerogel is not like conventional foams, but is a special porous material with extreme microporosity on a micron scale. The individual pores are only a few nanometers in size. A nanometer is one billionth of a meter. Aerogel’s insulating power is not dependent on loft. For example, the average sized adult exerts a force of 16-17 psi on a insole, which would result in a significant loss of thermal performance of a closed-cell foam insole, but an insole containing Aerogel is unaffected by pressure.
This is similar to the demo for Toasty Feet Insoles that Polar Wrap has at the Outdoor Retailer Show. The thin insole containing Aerogel insulates a foot from -106 °F dry ice. The normal foot temperature is 72 °F.
The Toast Feet Insole contains Aerogel, developed for NASA, and claimed to have the highest thermal insulation (R-Value/inch = 12) of any solid material available.
A disk of Aerogel (right) is translucent and feels weightless. The Aerogel inside the Toasty Feet is a powder imbedded in the core of the insole (left).
To put Aerogel in an insole, Polar Wrap infuses it as a powder into a carbon-based fabric. So how does it insulate if it’s a powder? The answer is Aerogel is a nanotechnology as explained above - each particle has nanopores (nanometer sized pores) containing air, so the dead air space is there to provide insulation.
The basic Toasty Feet model is a flat insole with a dimpled polyester upper fabric and smooth neoprene lower surface. It does not provide arch support and zonal padding like many replacement footbeds for hiking shoes. Its “sole” purpose seems to be padding and insulation. Cushioned, arch support, and magnetic models, all containing Aerogel, are available.
The top surface of the basic Toasty Feet Insole is dimpled and the lower surface is smooth. Three sizes are available for men, women, and kids respectively; each one is trim-to-fit (right).
We tested the Toasty Feet basic insoles in many different types of footwear as part of our Lightweight Footwear for Snow Travel project. We found them to be very light (2.3 ounces/pair for the men’s model and 1.8 ounces/pair for the women’s model) and noticeably warm. They did their job well, namely keeping the bottom of our feet warm.
The downside of the Toasty Feet Insoles is they are not very durable. Although the bottom is claimed to be neoprene, which is a very durable fabric, it does not appear to be neoprene at all. The patch pulled out of the left insole was from some adhesive in the bottom of a shoe that stuck to the insole. The right insole is cracked around the periphery and the Aerogel is leaking out.
We also note that the toe area (above the first dotted line) is not insulated with Aerogel. Will did not need to trim the insoles to fit his size 12 shoes, which means the toe area was not insulated by the insole. Janet trimed hers down to a women’s size 7, so the toe area of her insoles was insulated with Aerogel.
Overall, we were pleased with the light weight and insulating performance of the Toasty Feet Insoles, but we were disappointed with their lack of durability. Also, for larger foot sizes (larger than a size 7 for both men and women), the toe area is not insulated. The Toasty Feet are a good value at $12.95.
Features and Specifications
- Manufacturer: Polar Wrap (www.polarwrap.com)
- Product: Toasty Feet Insole, basic model
- Models Available: Men’s, women’s, kid’s, arch support, cushioned, and magnetic
- Sizes: Each is one size, cut to fit
- Features: Dimpled top surface for increased comfort and ventilation, Aerogel insulation
- Weight: Measured weight for the men’s basic model is 2.3 oz/pair (65 g), and women’s model is 1.8 oz/pair (51 g); manufacturer specification for the men’s model is 2.7 oz/pair (77 g), and 2.1 oz/pair (60 g) for the women's model
- MSRP: $12.95 for the basic model; cushioned, arch support, and magnetic models are $16.95