Low Slope Roof Insulation

Low slope roof insulation is crucial for improving the energy efficiency, comfort and living standards in buildings.

Find products Contact Us Why ROCKWOOL on the roof? Download our guide
Dual Density Roof Roofing photo

Whether your roofing project is part of a new construction or an existing building rehabilitation or repair, you can begin maximizing your roof’s long-term durability and environmental impact as early as the design phase.

Incorporating stone wool insulation into your roof assembly provides options for enhancing acoustic performance, passive fire protection, reliable long-term R-value and dimensional stability. Moisture-tolerant properties of stone wool even allow for insulation reuse long after other roof assembly materials have reached the end of their service life.

 

 

Table of contents

  1. Roof Insulation Products
  2. Why do we need low slope roof insulation
  3. Why choose ROCKWOOL solutions
  4. Very Severe Hail
  5. Wind Uplift
  6. Solutions
  7. Case Studies
  8. Downloads and resources
  9. FAQ

Assembly Solutions

Stone wool insualtion can be used in either full-height stone wool or hybrid low slope roof assemblies. Explore common stone wool applications 

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Very Severe Hail

ROCKWOOL stone wool insulation can be used as a coverboard in Very Severe Hail (VSH) regions.

Learn more about these systems.

VSH and Stone Wool
Roof Insulation Application Guide
Application Guides

Download our Roofing Insulation Application Guide

Your Application Guide to Roofing Assemblies and Insulation Solutions for Commercial Construction.

Download

Roof Insulation Products

Lionsgate Film Studio Case Study

ROCKWOOL Toprock® DD

Used as a roof insulation or insulating cover board over other insulations, ROCKWOOL Toprock® DD is a high-density stone wool insulation board for low-slope roofs.

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Flat roof, FRI, Metal Box, étanchéité bitume, bitumen roof-board, Rockfleece B Energy

ROCKWOOL Toprock® DD Plus bitumen coated low slope roof insulation

Compatible as the substrate for torched and hot-mopped membrane attachment types, ROCKWOOL Toprock® DD Plus is a high-density, bitumen-coated stone wool insulation board.

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Flat Roof Refurbishment Application - Stopsley High School

ROCKWOOL Multifix™ mineral coated fiberglass faced low slope roof insulation

Multifix™ is a dual-density, mineral wool insulation board with a glass fiber coating for flat roofing applications, compatible with multiple attachment methods including self adhered, cold adhered, liquid applied and torch applied membranes

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Low Slope Roof Fabricated Components Full Roof Render Detail - Unfaced Roof Components

ROCKWOOL Toprock® Tapered, Flute Filler, Cant Strip low slope roof fabricated components

Low slope roof fabricated components compatible with a variety of membranes and membrane types, air/vapor barriers, fasteners, and adhesives

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Why do we need low slope roof insulation?

As heat rises, most energy loss is usually through the roofing area. Low slope roof insulation is an essential tool that can enhance the energy efficiency of a building and reduce fuel costs.

Creating more effective low slope roof barriers also offers your building further protection from the unpredictable outdoor climate, including overheating in warmer climates and rain and snow in cooler regions.

From high rise apartment blocks, to residential designs, industrial units, large commercial facilities and schools or hospitals, flat roofs are an integral part of modern building design.

Constructions such as terraces, rooftop gardens, blue roofing with water retention and roof spaces which are used for solar purposes are becoming ever more popular. This growing trend for functional roof spaces brings even more demand for effective insulation, helping to enrich the space available on top of your building.

Relevant resources
7 facts about. Durability and stone wool insulation
PDF
251.0 kB
8 facts about. Stone wool’s mechanical performance
PDF
293.2 kB
Improving Value with Stone Wool Roof Systems
PDF
2.9 MB
Flat roofs are the umbrella generating spaces to live and work.

Kim Brandt

ROCKWOOL Group Product Manager

Stone Wool Insulation in Low Slope Roofs

When designing and building a roof system, achieving the greatest performance and resilience comes from selecting the right products for your project. ROCKWOOL low slope roof insulation products can be used to help minimize the fire, sound and long term performance risks of your project.

With numerous ROCKWOOL stone wool products available, you will find insulation options that support optimizing system cost, thermal performance, fire and acoustic resistance and long term durability.

Fire resistant:
Noncombustible, stone wool roof insulation products can be used in Class 1 roof deck construction and are classified as a non combustible core (NCC) roof insulation under FM 4470.

ROCKWOOL roof products are suitable for WUI zone construction, and are listed within the California Office of the State Fire Marshall’s Building Materials listing.

Learn more about CAL FIRE listings

Sound absorbent:
The non-direction fiber orientation and increased mass effectively reduces sound transmission, with performance that conforms to the 2015 International Green Construction Code’s OITC and STC requirements for buildings in close proximity to high noise sources

Find acoustic rated low slope roof solutions in out assembly catalog.

Download our roof acoustic catalog

Durable:
Dimensionally stable and providing long term thermal efficiency, stone wool roof boards maintain their structural integrity even when exposed to hail and wind.

ROCKWOOL roof board products have been tested for severe and very severe hail (VSH) and is acceptable as a coverboard in VSH regions.

Learn more about stone wool insulation and VSH testing

Vapor-permeable and moisture-resistant:
Structural integrity of stone wool insulation boards are not affected by the presence of water, and the vapor permeability of stone wool can benefit a roof assembly designed to promote drying  

Sustainable:
Stone wool insulation is manufactured from one of the world’s most abundant raw materials without the use of blowing agents or toxic flame retardants, stone wool can contribute towards LEED credits for your project

ROCKWOOL products

Very Severe Hail (VSH)

A roof system must perform against severe weather events, with few being more devestating than hail.

FM Global provides designations for different levels of hail resistance across the US. The Very Severe Hail (VSH) level is the most stringent, followed by the Severe Hail (SH) and Moderate Hail (MH). Different ratings are appropriate where designated by the FM Global map and other requirements outlined in FM Global’s 1-34 Property Loss Prevention Data Sheet.

Stone wool insulation in Very Severe Hail Conditions

ROCKWOOL stone wool roof insulation products are tested and approved in roof assemblies as a coverboard, board stock and as a thermal barrier for use in Severe and Very Severe Hail conditions.

Stone wool insulation as a coverboard in very severe hail applications can provide performance benefits over traditional coverboard materials:

  • Added thermal performance of an insulating coverboard
  • FM4470 noncombustible core rated roof insulation
  • Moisture resistance
  • Dimensionally stable and durable solution
  • Lighter weight and improved handleability compared to many alternative VSH-approved coverboards

ROCKWOOL roof products have been approved in a number of VSH tested assemblies with various membrane manufacturers, including GAF, Siplast, and Tremco CPG. A complete list of VSH tested low slope roof assemblies with stone wool insulation is available by visiting roofnav.com

For a collection of tested assemblies with Severe Hail and Very Severe Hail ratings, download our Roof Application Guide.

Download the guide
ROCKWOOL solutions for flat roofs are durable and proven by more than 40 years of use. ROCKWOOL flat roof insulation is also non-combustible and will protect you, your building and inventory if a fire occurs.

Kim Brandt

Kim Brandt, Global Product Manager, ROCKWOOL

Wind Uplift

Roofs are exposed to elevated uplift pressures during wind events. A roof system can be designed to withstand these pressures by using enhanced
fastening techniques to secure the assembly materials to the structural deck.

FM Global’s 1-28

FM Global’s 1-28 Property Loss Prevention Data Sheet provides general guidelines
and wind pressure recommendations for common building shapes. Roof Navigator (RoofNav) lists all current FM Approved roofing assemblies and products. Visit roofnav.com to see the full list of FM tested assemblies using ROCKWOOL stone wool insulation.

CSA 123.21

CSA 123.21 is a Canadian standard used to evaluate the wind uplift resistance of membrane roof systems when they are subjected to dynamic wind load cycles.

 

ROCKWOOL stone wool products have been approved for use in both FM Global and CS123.21 listed assemblies with a variety of roofing manufacturers to meet your project’s specific uplift needs.

For a collection of tested assemblies with wind uplift ratings for both FM Global and CSA 123.21, download our Roof Application Guide.

Download the Guide ROCKWOOL Roof Products

Low Slope Roof Applications

ROCKWOOL offers product solutions for conventional roof assemblies in new construction and the re-cover or re-roof of existing building projects.

New construction:
Choose a stone wool insulated assembly for maximum fire resistance and acoustic performance. Alternatively, a hybrid insulated roof assembly that incorporates rigid foam plastic insulation allows options for added fire protection and thermal performance by using stone wool as either an insulating coverboard or as the thermal barrier.
Re-cover:
Where allowed by the local building code, a new stone wool insulated roof assembly can be installed directly over an existing assembly that has either a failed membrane system or one at the end of its service life.
Re-roof:
When a full roof assembly replacement is needed, a ROCKWOOL stone wool insulated roof can replace the existing insulation in its entirety or be placed above the existing rigid foam plastic insulation layers that are to remain.

ROCKWOOL stone wool insulation can be used in multiple ways in a roof assembly, utilizing either full-height stone wool or a hybrid approach.

Full Height Stone Wool Assemblies

Utilizing a full height stone wool solution can maximize the fire and acoustic performance of the roof system.  Full stone wool roof systems do not require a separate coverboard in the assembly, and lowers risk of a fire event when using full-height, noncombustible insulation in the assembly. The insulation is also thermally consistent from the deck to the membrane surface.

Download our guide for a list of full-height stone wool assemblies tested for fire performance, hail and wind uplift.

Download the guide

Mechanically attached

  1. Roof membrane system
  2. ROCKWOOL Toprock DD
    (multiple layers as needed)
  3. Air and vapor barrier
  4. *ROCKWOOL Toprock Flute Filler
  5. Structural deck

Mechanically attached assemblies can include single-ply membranes including TPO, PVC, EPDM, KEE. 

*Flute Filler not shown - can be installed in metal deck assemblies

Toprock DD - Metal Deck - Full Height Stone Wool Assembly - Mechanically Fastened

Torch or adhesive assembly

  1. Roof membrane system
  2. ROCKWOOL Toprock DD Plus
  3. ROCKWOOL Toprock DD
    (base layer if multiple layers needed)
  4. Air and vapor barrier
  5. *ROCKWOOL Toprock Flute Filler
  6. Structural deck

Torch or adhesive applied systems for multi-ply roof assemblies including SBS, APP (modified bitumen). 
ROCKWOOL Toprock DD Plus is designed for torch applied memebrane systems, with Toprock DD unfaced insulation as additional thermal insulation in the assembly.

*Flute Filler not shown - can be installed in metal deck assemblies

Toprock DD Plus - Metal Deck - Full Height Stone Wool Assembly - Torch Applied Membrane

Cold-Adhered assembly

  1. Roof membrane system
  2. ROCKWOOL Multifix or *Toprock DD Plus 
  3. ROCKWOOL Toprock DD
    (base layer if multiple layers needed)
  4. Air and vapor barrier (varies)
  5. Structural deck

Cold-adhered assemblies including TPO, PVC and KEE; torch or adhesive applied for multi-ply roof assemblies including SBS, APP (modified bitumen).
The mineral coated fiberglass facer on ROCKWOOL Multifix is compatible with a wide range of membrance attachment methods.

*Toprock DD Plus can be used with certain attachment methods 

Multifix - Concrete Deck - Full Height Stone Wool - Cold-adhered Membrane

Hybrid Roof Assemblies

Utilizing a hybrid insulated assembly that includes stone wool insulation together with rigid foam plastic insulation allows options for added fire protection and thermal performance while minimizing the roof assembly height by using stone wool as either an insulating coverboard or as the thermal barrier.

Download our guide for a list of full-height stone wool assemblies tested for fire performance, hail and wind uplift.

 

Download the guide

Insulating Coverboard

  1. Roof membrane system
  2. ROCKWOOL Multifix, Toprock DD, or Toprock DD Plus 
  3. Polyisocyanurate insulation
  4. Air and vapor barrier
  5. *ROCKWOOL Toprock Flute Filler
  6. Structural deck

Stone wool when used as the top layer as an insulated coverboard acts as a thermal
buffer for the roof membrane, increasing the acoustic performance of the assembly, and removing the need for a separate coverboard.
ROCKWOOL stone wool insulation products are components of tested and approved roof assemblies as a coverboard in Very Severe Hail rated assemblies, and in assemblies tested for wind uplift. 

*Flute Filler not shown - can be installed in metal deck assemblies

Toprock DD Plus - Metal Deck - Hybrid Roof Assembly - Coverboard - Light Membrane

Thermal Barriers

  1. Roof membrane system
  2. Coverboard
  3. Polyisocyanurate insulation
  4. ROCKWOOL Toprock DD
  5. Air and vapor barrier
  6. *ROCKWOOL Toprock Flute Filler
  7. Structural deck

When using stone wool as the base layer in the roof assembly it acts as a thermal barrier to increase the fire resistance rating of the assembly.
ROCKWOOL Toprock DD unfaced stone wool insulation is the recommended product for this application.

*Flute Filler not shown - can be installed in metal deck assemblies

Toprock DD - Metal Deck - Hybrid Roof Assembly - Thermal Barrier

Recover Assemby

  1. Roof membrane system
  2. ROCKWOOL Toprock DD, Toprock DD Plus or Multifix

Exisiting Roof Assembly

  1. Roof membrane system, to remain
  2. Coverboard, to remain
  3. Insulation, to remain
  4. Air and vapor barrier
  5. Structural deck

Where allowed by the local building code, a new stone wool insulated roof assembly can be installed directly over an existing assembly that has either a failed membrane system or one at the end of its service life.
Stone wool insulation can act as an insulating coverboard in roof recover applications.

Toprock DD - Metal Deck - Hybrid Roof Assembly - Recover Assembly Exploded View

Case Studies

The project

Wayne State University is a nationally recognized metropolitan research institution with nearly 32,000 students. Annual maintenance evaluations identified a number of buildings on the campus with leaking roofs.

The problem

This case study looks into four of these buildings that underwent a re-roof or re-cover application where ROCKWOOL’s asphalt coated stone wool insulation was installed. The result of these upgrades resolved the water penetration issues and improved the long-term thermal performance of the roof assembly.

The solution

ROCKWOOL exclusive dual-density TOPROCK DD Plus with a higher
density top layer, provided a strong point load resistance and effective
load distribution – adding durability to the new re-roof/re-cover assemblies.

In order to meet the new ASHRAE standards, the addition of stone wool
insulation was a cost effective method for Wayne State University to both repair water penetration and improve the energy efficiency of all four
buildings.

Read more about Wayne State University's Thermal Performance

 

 

Find more case studies
Wayne State case study roofing

Downloads and resources

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FAQs

How thick should flat roof insulation be?
Do you need to ventilate a warm flat roof?
What is a cold flat roof?

Contact Us

Dave Lawlor, National Sales Manager

Canada, Mexico Export

dave.lawlor@rockwool.com

905-699-3861

Joseph Donnelly, Technical Sales Specialist

United States

joe.donnelly@rockwool.com

484-426-7444

[1] https://www.rockwoolgroup.com/why-stone-wool/

[2] WHO Housing and Health Guidelines - https://www.ncbi.nlm.nih.gov/books/NBK535294/

[3] https://www.rockwoolgroup.com/why-stone-wool/robustness/

[4] https://www.rockwool.com/applications/marine-offshore/firesafe/

[5] https://www.rockwoolgroup.com/why-stone-wool/thermal-properties/

[6]https://www.rockwoolgroup.com/siteassets/media/brochures/rockwool-product-capabilities-brochure-aw-final.pdf

[7] https://www.nfrc.co.uk/docs/default-source/form-protected-documents/homeowners/householders-guide-to-flat-roofing-2015.pdf

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