Benefits of Foaming the Roof, Should I use Open or Closed Cell Foam?
One of the first jobs I sprayed with foam in 2009 was my own roof. Many people ask me for bids, for their existing home roof and that is something I am always excited to talk about as it is “the best thing they can do to increase comfort, reduce costs of heating and cooling and reduce or eliminate hot/ cold spots in their home” depending on where they are.
So, what is the right answer to the Open vs. Closed Cell on a roof deck? Well, the answer depends on many different factors. I always prefer with approaching these issues with “what is your goal” or “what is the problem to solve.”
Using open-cell spray foam insulation on the underside of roofs in Chicago, as opposed to closed-cell spray foam, offers several significant benefits related to climate adaptation, cost is one but the most important advantage is, that closed cell foam as a moisture/ vapor barrier when sprayed to the appropriate depths at the roof will also stop simple roof maintenance issues from being easily corrected. Inevitably, when a storm comes through, there is always a chance of a shingle getting out of place, a bit of caulking to wear out or come off, a bit of flashing to be out of place… all things that if the roof is foamed with closed cell foam will continue unseen for years until it causes a major issue with the deterioration of the framing, materials that have been soaked. All things that could have been avoided by doing proper moisture management in the home/ roof/ attic and not by using a closed cell moisture barrier foam at the roof.
This list is not comprehensive of all issues and there are many variations that would fall outside of this simple list! This list is meant to hit the highlights that will apply to most potential customers.
1. Moisture Management:
Using open-cell spray foam insulation at a roof (To a proper depth depending on the specific issues, closed cell foam must be used in issues where the framing depth will not allow enough open cell foam) in Chicago, as opposed to closed-cell spray foam, offers several significant benefits related to climate adaptation, cost is one but the most important advantage is, that closed cell foam as a moisture/ vapor barrier when sprayed to the appropriate depths at the roof will also stop simple roof maintenance issues from being easily corrected. Assuming that all of the previously listed items as well as any other issues with moisture intrusion into the home via walls, roof, crawl space, basement slab, sump pits, etc… at some point, a storm comes through, there is always a chance of a shingle getting out of place, a bit of caulking to wear out or come off, a bit of flashing to be out of place… all things that if the roof is foamed with closed cell foam will continue unseen for years until it causes a major issue with the deterioration of the framing, materials that have been soaked. All things that could have been avoided by doing proper moisture management in the home/ roof/ attic and not by using a closed cell moisture barrier foam at the roof. In all structures using spray foam to significantly tighten up the envelope, it is critical that moisture management be part of the overall plan. Use of rain screen materials and proper sealing of water sealing at walls and roofs.
2. Cost Effectiveness:
Open-cell spray foam is significantly less expensive than closed-cell foam per inch and per R (R value measures the resistance to heat flow of all material.. This cost benefit makes it an attractive option for projects AND because it is the right product, where the space allows. In issues where there is not enough framing depth or other issues require more R per inch, then we must use closed cell and do proper evaluations of the roof to ensure there are no shingles out of place, flashing issues or other issues allowing moisture into the roofing assembly.
3. Insulation and Energy Efficiency:
While closed-cell foam has a higher R-value per inch (Closed Cell Foam varies dramatically from 4.5-7.4 per inch for typical name brand products sold and used in residential and Commerical applications for insulation), open-cell foam still provides substantial insulating properties that are appropriate for Chicago’s thermal needs, as an air barrier/ insulation. Open-cell foam has an R-value of approximately 3.5 to 4.5 per inch, which can effectively insulate against Chicago’s winter temperatures when applied at appropriate thicknesses. This helps in reducing heating costs in winter and cooling costs in summer by maintaining a stable internal temperature. The rule of thumb is a foam roof deck can reduce the air conditioning tons of cooling by 50% and BTU needs by 2/3. In my own home when installing a new HVAC I went from 3 tons of cooling to 1.5 and from 180,000 BTU’s to 60,000 BTU’s.
4. Sound Dampening:
Open-cell spray foam provides excellent sound absorption properties. Its softer, more flexible texture helps to reduce the transmission of sound, making it ideal for urban environments like Chicago where planes and helicopters fly overhead regularly or where we desire to listen to our music at our preferred volume and do not want the neighbors to complain. (Not simple for multi family issues between units but it does help dramatically if the lower space ceiling is wide open)
5. Structural Flexibility:
The flexibility of open-cell foam is more accommodating to the natural expansion and contraction of building materials caused by Chicago’s significant temperature swings. Unlike closed-cell foam, which is rigid and can exert pressure on the roof structure as it expands and contracts, open-cell foam compresses and expands, reducing the potential for structural stress. In some cases open cell foam can flex as much as an inch during expansion and contraction and maintain adhesion to the framing. Closed cell foam wil add as much as 200% structural integrity to a building.
6. Sustainability:
Open-cell foam uses water as the blowing agent, which results in a lower environmental impact compared to the hydrofluorocarbons (HFCs) used in some closed-cell foams. This makes open-cell foam a more environmentally friendly choice, aligning with sustainable building practices and potentially contributing to LEED certification points. HFO closed cel foam is our preferred product for closed cell applications but that foam is more expensive and is not always available at a price required for all projects.
7. Extreme Weather and Safety:
In the event of high winds (Tornadoes or straight line winds from storms) or fires around your home, the unvented attic assembly of a foam roof reduces the chance of your roof being torn from the house and it also stops the typical pathways for embers from fires to get into your naturally vented traditional soffit to start a fire in your home! Lots more here on “Unvented Attics”
In summary, while both open-cell and closed-cell spray foam have their respective places in building construction, the specific benefits of open-cell foam—like moisture management, cost-effectiveness, good insulation properties, enhanced sound dampening, structural flexibility, lower environmental impact, and ease of installation—make it particularly suited for residential and commercial buildings in Chicago. This aligns well with the city’s architectural styles, climate conditions, and energy efficiency goals, making it a sensible choice for many projects.
With ten years of experience selling spray foam insulation in Chicago, Tom Decker is THE person to call and the Chicago Green Insulation is the organization to hire when you are looking for top notch quality and performance as well as someone who can deal with the needs of code officials, home owners and general contractors. Call the others in Chicago, if you are interested in the cheapest price, call Chicago Green Insulation if you are interested in using your dollars to make Chicago a better city for all of us!
Chicago Green Insulation
Chicago Green Insulation
Chicago Green Insulation
Chicago Green Insulation
Chicago Green Insulation
Chicago Green Insulation