What is polyurethane insulation? Polyurethane spray insulation foam is a heat activated polymer that is formed by two main chemicals usually referred to as Part A and Part B Isocyanate and Polyol Resin, is delivered by two hoses to the installers spray gun. Being mixed on site by the installer other chemicals are also introduced into the mix as flame retardants. There is a chemical reaction between Part A and Part B. The mixture is sprayed on the surface to be insulated as a liquid and expands to fill the void till it cures. There are two types – open cell and closed cell. Open cell makes for a lighter cheaper end product, closed cell allows for a more waterproof end product with an increased R value, this obviously comes at a greater cost.


Isocyanates are toxic chemicals until they have reacted and cured fully. Generally the period of 24 to 72 hours is given for the product to be fully cured. However, the curing time all depends on how it has been mixed and the ambient temperature. Whilst it has not cured it will off gas. You only have to look at the clothing that installers have to wear to protect themselves – full cover overalls including complete head cover, goggles and respirator, gloves so as not to expose any skin – I can only feel compassion for these guys. If chemicals are not mixed properly they could cause delayed curing with lingering odour causing probable health problems to the inhabitants of the home.

In the US OSHA (Occupational Safety and Health Administration) say that exposure to isocyanates can cause respiratory ailments and that isocyanates include compounds classified as potential human carcinogens. These chemicals are the leading cause for work related respiratory ailments, asthma, etc, in some cases fatal reactions have occurred. Occupants of homes who have had polyurethane insulation installed must stay away from the home for at least 24 hours. Permanent asthma can occur very quickly depending on the level of exposure to isocyanates in some cases in just a few hours after exposure.

My personal experience with polyurethane foam insulation – My son and I were commissioned to remove polyurethane foam that had been sprayed in between the tile battens and on top of sarking, however the problem was that the foam came into contact with the roof tiles and with deterioration the insulation was drawing rain water from the tiles and the roof was leaking. As concrete tiles hold their own weight in water when it rains it is best not to have anything come in contact with them.

Over the years the polyurethane had become chalky and at least 40% of it was dust, when we lifted the tiles the dust blew everywhere. It took us 3 days to lift the tiles, remove the polyurethane chunks and vacuum the dust that did not blow away and then replace the tiles to completion.

I understand that once cured SPF will not off gas however as it had lost its integrity and went to dust. My son and I were breathing this over a period of three days. Getting off the subject I had my left kidney removed with 66mil cancerous tumor that was 4 years ago now, at the time I had to wonder how I got this cancer. Was it any number of things that I had been exposed to during my 50 years as a roofer, then on researching for this blog I asked myself did removing that polyurethane foam insulation have something to do with it, I don’t know go figure.

Spraying polyurethane foam to the underside of any roofing material has got to be one of the most ridiculous types of building practice I have ever come across in my 50 years in the roofing industry. In years to come I can see foam dust all over the ceiling of homes after being sprayed to the underside of roofing materials.

There are reports that SPF (spray polyurethane foam) has continued to off gas long after the 24 to 72 hours it is supposed to be fully cured, there are no guidelines for the homeowner for chronic exposure to the chemicals of SPF. I can’t see anything green about this product with all the ingredients being volatile chemicals. It all depends on the onsite installer, and the amount of chemicals in the mix, the ambient temperature, not unlike a witches’ cauldron.


It is my personal opinion this could have the same impact on consumers in the future as asbestos insulation has had. More than 1,000 homes in Canberra are now in the process of being demolished for the mere fact that they had asbestos loose fill insulation installed.

In conclusion I personally do not believe SPF is safe. Is polyurethane spray foam insulation safe? I will leave you to make your own decision.

Whether you have this product installed or not you will still need an effective roof ventilation system, however if you do install this product the need to have an effective roof ventilation system multiplies to become an absolute necessity. Universal Tile Ventilators have a system for tiled roof and we have the Smoothline Ventilator system for corrugated colorbond roofs.