After long hours of searching you have finally landed in the right place. At last the elusive answers to questions on insulation and spray foam are here awaiting your approval. These aren't the usual newbie FAQ's. These are the 'technical' questions only the really savvy home renovators ask. No more intense bouts of frustration where you suddenly find you're banging your head on the keyboard. The real answers to the advanced questions are here, so say goodbye to impressions of little squares on the forehead.
Does spray foam release any Volatile Organic Compounds (VOC)?
Polyurethane foam is not considered to emit VOC's. However, during application some spray foams release VOC's through the process of discharge from the canister. After curing there should not be any further emissions. To be sure, check with your foam supplier.
Can spray foam be used to insulate underground water pipes?
Yes! Work closely with the polyurethane manufacturer to determine the best method of application and the most beneficial kind of foam to use. Regional climate changes and projected temperature extremes will be a part of the decision making process. During application, be sure to prepare the trench properly so that no moisture is allowed on or in the foam until it has cured.
Should fibreglass insulation be removed before applying spray foam?
Yes! Many contractors opt for leaving blown in insulation in an attic and spraying the foam on top. The problem that arises is ventilation and temperature control. More clearly, the temperature of the attic floor will be different than amidst the fibreglass and the temperature amidst the fibreglass will be different than above the spray foam. The job of the spray foam is to balance temperature and humidity with the environment so condensation is prevented. With an inner layer of fibreglass, where air flows, the conditions would be perfect for moisture formation.
Does the surface where the spray foam will be applied have to be clean?
Yes! Any oil or dust on the application surface will prevent the spray foam from adhering. For the typical attic in a wood frame home, a careful vacuuming job covering every nook and cranny will often be adequate. For applications where the surface is steel (or any other metal) it is even more important for the surface to be free of dust and oil. In some cases where the steel is very new, a coat of primer will be required. Many spray foam manufacturers offer a simple rule: if it can be painted, it can be spray foamed.
Does an attic need to be vented if spraying foam on the rafters?
That depends. If you are applying the spray foam to the roof deck and gable walls, then you want everything under that surface to be a part of the temperature conditioned space. Vents in an attic with insulation above it would be much like have open windows year round - a total waste of money. If you are applying spray foam to just the attic floor, then the conditioned space is below the attic floor. Vents will be necessary for preventing excess humidity.
Is weather a factor when applying spray foam insulation?
Water is the most important consideration, either as rain or condensation. If there is any moisture present on the application surface, the spray foam will not adhere. Most of the time the problem will be seen right away, and the installer can stop the job until the surface is dry. In the case of applying spray foam to the exterior of roofs and walls during the construction process, wind will be a major factor as well. Overspray carried by wind can not only affect surrounding surfaces, it can mean a loss of yield.
Ambient temperature plays a role as well, albeit in extreme conditions. Exceptionally hot temperatures can cause the foam to not hold shape, cause risk to the installer in enclosed hot places and even risk explosion of the tanks holding the polyurethane. Freezing temperatures, such as in northern Alaska, may cause the applicator to cease working altogether. The substrate temperature is a factor as well. For unique situations such as these, it is best to consult with the manufacturer to see how best to proceed.
There are likely many more advanced questions concerning spray foam insulation out there, and in all good faith we intend to cover them in follow up articles. Nevertheless, the humble offering of information laid out above is here for the benefit of all readers. Go forth and spray your polyurethane foam!