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What is the Best Way to Insulate a Vaulted or Cathedral Ceilings?

Insulated Vaulted Ceiling Blogs

If your home has vaulted or cathedral ceilings, you already know that things can get toasty in the summer. This article is for homeowners that want to insulate their ceilings, without having to install new drywall that covers exposed members. Is there a way to fix heat trapped in high ceilings? Can 'purple panels' help with insulation? Here we'll show you how Structural Insulation Panels (SIPs) can help insulate your home without changing your existing ceiling.

How to Insulate a Vaulted Ceiling with Ray-Core SIP Panels

SIP Panels - PV Vaulted Ceiling - Before

The best way to insulate vaulted or Cathedral ceilings without covering the exposed beam or wood ceiling. While the project I’m referencing took place in Palos Verdes Estates, it can be applied anywhere. I recently used Ray-Core Inc. SIPs to help us preserve the interior look of the vaulted ceiling while providing the much-needed insulation. 

Homes with vaulted ceilings can experience warmer temperatures as a result of not having insulation, a common problem amongst Mid-Century Modern and California Ranch style homes. Vaulted ceilings with exposed lumber typically have little to no insulation. The lack of insulation causes heat to radiate from the ceiling especially during the hot summer months. The opposite is true in the winter, heat escapes through the ceiling and the roof, causing an increase in heating costs. Historically, contractors andSIP Panels - Traditional drywall remodelers have tried to remedy this by installing insulation between the ceiling purlins and covering the entire ceiling with drywall to hold the insulation in place. But there are issues with this technique, in most cases, the ceiling was not designed or engineered to carry the additional weight of the drywall. That is where SIPs have a clear advantage.

What are structural insulated panels?

Structural Insulated Panels (or SIPs) are a form of 'sandwich panels' that consist of an insulated foam core, sandwiched between two layers of structural board that can be used as a building material. These SIP panels are the best option for owners that want to preserve the unique interior look of an existing vaulted ceiling because SIPs are installed on the exterior side of the roof.

How are structural insulated panels installed?

If you are planning on installing a new roof (complete replacement) you'll really want to get SIPs installed. The added weight will mean you will need a structural engineer to design a 'roof plan' that incorporates SIPs and radiant barrier OSB sheathing to really maximize your results. We highly recommend finding a licensed structural engineer that will provide installation details and will ensure the roof framing will not be overloaded (stressed or too heavy). There are other rigid core insulation products (like EPS & XPS) that are cheaper but don’t offer the same level of performance.

TIP: I don’t recommend using 1-inch purple foam panels that are commonly found in big box stores (Home Depot or Lowes) they will not make much of a difference, you might still experience warmer temperatures radiating from the ceiling.


What benefits do RayCore Structural Insulated Panels (SIPs) provide?

SIP Panels - Raycore polyiso - versus - xps eps SIP panel - wall frame panel

Structural Improvement

The SIP panels are structural members (it's in the name), they are available with oriented strand board (OSB) or structural plywood. They can help improve the home's integrity against lateral (shear) loads and vertical (gravity) loads. Bottom line, it makes your home much stronger. Since they are made of foam, the panels are lightweight and easy to handle, making installation a breeze.

Example: In our Palos Verdes Estates remodel we designed & built a new Spanish clay-tile roof that incorporated Ray-Core SIPs. The SIP Panels provided additional strength (sheathing) to the roof system and provided an R-Value equivalent to nearly 20-inches of traditional fiberglass insulation.

Fire Resistance Qualities

The chemical composition of Polyisocyanurate (the thermoset plastic used in SIPs) has flame retardant qualities. If you were to light a torch against a Ray-Core SIP, the panels would scorch but would not ignite. This is a big plus for homes in high-risk fire zones. Most homes in California are in a high fire hazard zone. During wildfires, fires and fire embers spread from roof to roof. Modern clay tiles also provide a good fire rating that can be improved when paired with SIP panels like those from Ray-Core Inc.


Assembly and Installation

In the picture below you can see a cross-section of a Ray-Core SIP panel assembly. The SIP panel hasSIP Panels - Assembly - Cross Sectionan integrated 2-by lumber stringer that is used to attach the panel to the existing roofing framing. You can also see the plywood sheathing covered by Boral TileSeal, a peel and stick waterproof roof underlayment. Ultimately the roof tile is attached on top of that membrane.



Since the Ray-Core SIP panel is attached externally on the outside of the roof frame, there are no cosmetic changes to the interior ceiling, and there is no damage to the tongue & groove boards. In the picture below, you can see there was no change to the interior ceiling.  

The roof sheathing is attached over the RayCore panels and then the roof tiles or shingles are attached to the OSB. This keeps the roofing nails from penetrating the tongue and groove and keeps the ceiling in the house looking pristine.

SIP Panels - exterior tongue & groove ceiling SIP Panels - osb sheathing - boral tileseal - underlayment

What is the Cost of Insulating a Vaulted Ceiling or Cathedral Ceiling with SIP Panels?

SIP Panels - vaulted ceiling after

Ok, so let's get down to what you’re really wondering! What is the cost? Installing a new roof is a big job. Homeowners will need to consider the total cost of insulating their Vaulted or Cathedral ceilings. In most cases, insulating the roof using Ray-Core SIP panels will add about $24 dollars per square foot to the cost of the new roof project. This equates to roughly between $38,000 to $48,000 for a 2,000 Square foot house. As of April 2021, the panels are made to order from the manufacturer in Idaho with a 4 to 6-week lead-time.

The cost of installing SIP panels and a new roof can be substantial, a purchase that homeowners will need to carefully consider. In my experience, the homeowners that are fed up with high indoor temperatures often choose to invest in a new roof with SIP insulation. Remember, SIP panels can help reduce radiating heat that penetrates your ceiling, all while preserving the open look of a vaulted ceiling. 

Our goal is to provide our clients with the best information so that they know what they are buying.


about the author - alex rodriguez general contractor - best contractor south bay


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