What do you mean by "our AC units require fresh air ventilation"? Fresh air doesn't come from the attic. If there's an atmospheric combustion appliance in the attic, such as an 80 AFUE furnace, then you shouldn't be encapsulating the attic anyway. If that's the case, you don't want spray foam on the roofline at all. You can either change out the furnace to a sealed combustion unit or do your insulating and air-sealing at the flat-ceiling level. https://www.youtube.com/v/ggLAUsiuI_o&feature=share
I did a LOT of prep before using this product. Cleaned, vacuumed, installed additional insulation etc etc etc. This spray foam was easy to work with, and did it's job as it was supposed to. If you are curious, this kit was purchased because - every "foam insulation company" I contacted either did not call back (due to no interest) OR this was too small of a job. That is why I went DIY on this one, that and: I was advised by one of these companies that they have a minimum $2k job because ... (insert your answer here, but I will choose that everyone needs to eat).
Was hesitant to buy this product because of some of the reviews but glad I did. It does just what it says and we even got the square footage out of it. You just need to read ALL the directions first and it wouldn't hurt to read some of the helpful hints in some of the reviews. It does only cover 1 inch at 600 square feet and is extremely easy to apply. Very satisfied customer!
Polyurethane is a closed-cell foam insulation material that initially contains a low-conductivity gas in its cells. As a result of the high thermal resistance of the gas, spray polyurethane insulation typically has an initial R-value around R-3.4 to R-6.7 per inch. In comparison, blown fiberglass typically has an R-Value of only R-3 to R-4 per inch.
Solvent-based polyurethane coatings have excellent adhesion and when used as a base coat over asphalt, EPDM, TPO or PVC, it eliminates the need for a primer. The resulting savings on labor and material more than offsets the higher cost of the product. When top coated with silicone, it gives you the best of both worlds. It's also an excellent gutter and RV coating.
Acrylic coatings are typically applied in two coats, with the second running perpendicular to the first. 1 gallon per 100 square feet is a good estimate for these coatings, as they do not need to be applied nearly as thick as many other coatings. These coatings can be sprayed or roll-applied. Acrylic coatings generally require a re-coat within 2-3 years of application. http://youtube.com/watch?feature=player_embedded&v=ggLAUsiuI_o
Spray Foam Hot Roof
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I used this for the rim-joist in our home. A couple things: I put 1in solid core foam (cut to size) in each bay before using the spray foam. I also was able to do a relatively 'thick' spray to close off any potential gaps that may have existed. I turned off the HVAC and turned on some fans in the windows to exhaust out the fumes, and wore a mask (3m respirator).
To avoid the expense re-roofing a house that is simply suffering from nail fatigue, and to obtain optimum insulation, an 85mm layer of polyurethane foam can be sprayed onto the underside of the slates or tiles of a pitched roof. This stabilises and weatherproofs the roof by fixing the nails, battens and roofing felt. As the foam is a superior insulant, coupled with just 100mm of insulation at joist level, your roof will also meet the stringent thermal performance standards required for a new home. A typical roof can be insulated using the polyurethane treatment for around half the cost of re-roofing.
These coatings contain various types of acrylic polymer, and are typically formulated to help extend the coating’s life and improve durability. Acrylic coatings are available in a number of colors but are most commonly used as white reflective coatings. Thanks to its durability and low cost, many contractors and facility managers believe this to be the best roof coating.
Silicone based coatings can be spray or roller-applied, and should utilize a medium-nap roller when rolled. These coatings are applied anywhere from 2 to 3.5 gallons per 100 square feet, depending on the substrate. Silicone has two major advantages over the other four types of coatings that should be considered when searching for the best roof coating: 1) it can resist ponding water for extended periods of time and 2) it can adhere to most substrates without a primer. Because of these two major advantages, silicone is the best roof coating that satisfies both quality and cost-effectiveness.
The average price to cover 200 square feet with a foam insulation kit will run between $300 and $600 (about two to three kits). Inside these kits is something called Icynene, a foam made from two liquids that are heated and pushed through a gun on the can. When Icynene is released, it expands up to 100 times its size as it hits the surface area you're covering. These can contain a lot of gasses, making its installation a dangerous process. Even low-pressure sprayers can be harmful to homeowners' health.
Both high and low-pressure, two-component spray foam are applied by professional contractors who are trained to use and apply SPF with the required equipment (protective gear, full eye protection, respirators, and gloves). Contractors should follow the ventilation recommendations by the product manufacturer to avoid overexposure through inhalation, and instruct those without protective gear (homeowners or building occupants) to stay away from the work area during exposure times and to not return until instructed by the professional contractor.
We are turning our roof into an unvented roof assembly by raising the roof and blowing in SPF. We are planning to leave the existing vapor barrier down but remove the fiberglass batting and then adding 6" of SPF in all the cavities, to completely seal and insulate the house. Should we have any concerns about doing it "upside down" and not spraying the foam directly to the underside/sheathing of the roof?
Spray Foam Under House
Yes, a new roof should be coated if the building owner wants to add a highly reflective roof coating to reduce energy costs. The buyer should be aware of any warranties provided for a new roof that may violate that warranty during the period it is in force via the use of a roof coating. This will extend the roof’s service life. A reflective roof coating will reduce the heat load on the roofing assembly. http://www.youtube.com/v/ggLAUsiuI_o?version=3