[Expert advice] PU foam sealant: DIY or professional?

The market for polyurethane foam sealants offers two main types of can: the so-called DIY can with a plastic straw and the professional can with a gun valve. It is commonly assumed that straw foam is used by home improvers who need it very rarely and therefore have no reason to pay for a professional gun, while professional installers prefer professional foam because a gun is more convenient and faster to work with and because the foam itself performs better than the DIY grade. But is professional foam really better on every count?

Where the difference comes from
The difference between DIY and professional foams comes mainly from the different conditions under which the foam passes through a plastic straw and through a gun. Formulators know this and adjust the recipes of DIY and professional foams accordingly, but the difference created by the straw and by the gun cannot be evened out completely.

Foam yield
With the same amount of product in the can, the foam yield is higher for professional foam. The design of the gun and the way it is adjusted also affect the yield and other properties of the foam. An experienced installer will always be able to set the gun up for the best result the foam can give.

Foam structure
Foam from a can with a straw forms a denser structure than foam from a can dispensed with a gun. That follows directly: the lower the yield at the same mass, the higher the density.

Thermal insulation performance
Several factors affect the thermal insulation performance of a foam, and density is one of them. The denser the foam, the better the insulation it provides. So the denser foam from a can with a straw insulates better than foam dispensed with a gun.

Post-expansion
This is an important parameter. It shows how much a fully cured foam grows in volume compared with the freshly applied one. Here the difference between DIY and professional foams is huge: depending on the formulation used by each manufacturer, post-expansion of professional foam ranges from 15 to 60% (15-30% for KUDO^® PROFF ABSOLUT and up to 25% for KUDO^® TREND), while DIY foam expands by 200 and even 300%. This has to be allowed for during application: apply too much foam, and as it expands it will press on the window or door frame and may distort it. DIY foam therefore has to be applied into the opening in smaller amounts, allowing for the fact that it expands 5-10 times more.

Application temperature
The application temperature range of professional foam sealants is considerably wider than that of DIY foams, especially at low temperatures. The professional foam KUDO^® ABSOLUT PROFF 65++ ARKTIKA NORD, for example, still works with the can at temperatures down to -10°C and outside air down to -25°C, while the DIY foam KUDO^® HOME 50+ ARKTIKA works with the can cooled only to 0°C (0°C is the best figure on the market for a DIY foam) and ambient temperatures down to -12°C. KUDO^®'s own technologies make it possible to produce a DIY foam that works at lower temperatures as well, but its other properties would suffer and its price would rise sharply.

So, all other things being equal, professional foam gives a higher yield, lower post-expansion and a wider application temperature range. DIY foam, in turn, has a denser structure and better thermal insulation performance.