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Spray Foam Insulation Underside For Metal RoofBy admin
Thursday, 8 November 2018
Metal is one of the best thermal conductors around. There is a reason why pans are made from stainless steel. And it all comes down to metal’s ability to retain as much heat as possible.
Conventional radiators are also made from steel. The goal is to allow the heat to radiate through the surface as quickly as possible. Unfortunately, this tangible temperature discrepancy between the warmth of the metal, and the cold air outside, leads to all manner of issues.
This article explores some of the main issues with metal roofs, and why provided you plump for a professional, spray foam offers a savvy, long-term solution to these common conundrums…
Condensation: The Crux of the Matter
During the summer, since metal is a great conductor, heat easily, and quickly, passes through the metal, making your building extremely hot.
One of the best ways to prevent this is installing spray foam insulation underside for metal roof. Why is spray foam best? Well, when you think of conventional insulation products, such as mineral fibre batts or insulation boards, they are largely unsuccessful in preventing condensation.
Batts and boards are placed edge to edge, meaning they do not form a continuous barrier. Thermal leakage and air leakage are to be expected.
The air that comes carries water vapour, that quickly condenses beneath the metal cladding. Condensation accumulates, and once there is enough, it will drip down onto the insulation, and eventually find its way through joins in the structure.
Spray foam, on the other hand, prevents condensation and eliminates the problem entirely.
Why Spray Foam?
Thankfully, there is a better insulation option for metal roofs than conventional fibre batts and insulation boards. Spray foam forms a continuous, air-tight seal under the metal roof in question. Spray foam fills all the holes, gaps, and cracks. The result is a superior insulation solution.
Spray foamis applied directly to the underside, eliminating any gaps, and preventing the formation of condensation. The thickness is up to the contractor to decide, and mainly depends on the R-value you need to achieve.
The R-value in influenced by the area you live in. Some places require a minimum of 38, while others go up to a minimum of 45.
Another challenge is to limit the thickness on the first pass. Reduce the thickness to a few inches, and then allow it to dry, to reduce the amount of moisture directly against the metal roofing
Challenges to Consider
With every insulation material and project, there are always challenges to consider. Open cell spray foam is the most cost-effective way to insulate a metal roof.
However, any opening over 1/16” can cause the foam to expand onto the roof. Spray foam can be found in both slow expanding, and fast expanding varieties.
The former is perfect for ceilings and roofs, as the foam expands slowly, and fills all cavities in the process.
Another challenge is to limit the thickness on the first pass. Reduce the thickness to a few inches, and then allow it to dry, to reduce the amount of moisture directly against the metal roofing.
This will reduce the amount of heat generated on the panel during the application as well. You do not have to worry, your professional contractor already knows this.
There is a reason why spray foam is not recommended as a D.I.Y project. The biggest reason is that when applied improperly, spray foam is not as effective as advertised.
You can also use closed-cell spray foam, which achieves two times higher R-value per inch. However, the density is also higher, and that means you are using much more material to cover the same area. Considering the price is also higher, open-cell spray foam is a much more cost-effective option.
Can You Increase The Drying Potential?
We touched on the subject of condensation. The question is: can you improve and increase the drying potential of your insulation? The answer is yes. When applying spray foam insulation underside for metal roof, you can take one of the two following approaches:
The first one is to create a vent space from the soffit to the ridge below the roof sheathing. You need at least 1 inch in depth.
You will lose some R-value, but you can make up for it by installing continuous installation on the bottom of the rafters. The move will also reduce thermal bridging.
The second approach is a bit more expensive, and requires creating a vent space, soffit to ridge, on the topside of the roof sheathing, by installing 2x4s, and then another layer of sheathing over the structural sheathing.
Again, a professional contractor will help you with all the questions you have, and make sure you get the best value for your money.
You can use spray foam insulation underside for metal roof, but also for many more purposes. In terms of interior insulation, SPF is well suited for insulating metal walls, and metal roof panels
What is SPF insulation?
Sprayed polyurethane foam is insulation composed of polyol and isocyanate resin. Chemically combined, these two chemicals produce foam that can be applied to surfaces using a spray gun. There are two types of spray foam: open and closed cell.
The former is water and vapour permeable, but provides an air barrier, and noise barrier, for the building. Closed cell does not allow water to enter, but it is much more expensive than open cell spray foam.
You can always install open cell spray foam and a vapour control layer to prevent moisture, and still the price will be much lower than with closed cell foam insualtion.
You can use spray foam insulation underside for metal roof, but also for many more purposes. In terms of interior insulation, SPF is well suited for insulating metal walls, and metal roof panels.
Because of the inherent physical features, as well as the spray application method, SPF can overcome any obstacle, and penetrate the hardest to reach areas.
Here are some advantages of applying spray foam to the underside of a metal roof:
- Reduces your energy bills by 30 to 50 percent, by providing an air-tight seal that prevents heat loss and gain
- Reduces air leakage and air-infiltration. The result is a more consistent temperature in your home
- Increase the lifespan of HVAC equipment, as it reduces the requirements and their load of work
- Reduce dust and pollen infiltration
- Reduce the likelihood of mould
- Spray foam does not sag, shrink, and settle over time. The R-value remains the same
- Spray foam has the highest performance and R-value of all insulation products
- No other product provides air tight seal as spray foam
- Spray foam has a lifespan as long as your home. The product will never sag or settle
- Reduce noise by providing noise barrier for your home
When installed incorrectly, spray foam does not bring the R-value as advertised. Only a certified technician will be able to meet the desired thickness, density, and adhesion
Foam Insulation: Final Thoughts
When you use spray foam for insulation, and sealing a building with metal panels, you have to be careful of several things. Let’s summarise…
For starters, you always need to hire a certified spray foam technician. As mentioned previously, spray foam receives a bad reputation, because of improper installation.
When installed incorrectly, spray foam does not bring the R-value as advertised. Only a certified technician will be able to meet the desired thickness, density, and adhesion.
Your contractor and technician will tell you, but it is important to know that spray foam can be applied only to clean and dry areas.
Always follow the building code requirements for fire protection.
Insist that your technician is careful, and that he prevents SPF chemicals from being drawn into the building’s ventilation system. Be careful of this during, and after installation.
Since you are applying spray foam on your metal roof, make sure to consult your metal panel manufacturer as well.
Ready to take the next step? Request your free roof inspection today by calling 0800 1700 636, or by simply clicking the button below!
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