Lightweight Insulating Concrete Systems FAQs
What is LWIC?
What happens if it rains while the contractor is installing the LWIC system?
Why LWIC Versus other insulation like ISO?
Installing over existing roofs.
How much does LWIC weigh?
How does LWIC provide UL Deck Fire Ratings?
Does LWIC contribute to Acoustic Design for buildings?
How does LWIC impact aging of roof membranes?
What happens if it rains on the lightweight before it is roofed?
How long does it take for the lightweight to cure and be ready to roof?
How long can LWIC stay exposed before installing the roof?
Why are there cracks forming in the LWIC?
Are roof vents required?
How is slope achieved with LWIC?
Can the Insulperm be left our overnight without having the top layer of lightweight concrete completed?
Can LWIC be installed over a painted metal deck?
How do we keep LWIC from pouring into the building below at openings in the deck on New Construction Projects?
What is LWIC?
Lightweight Insulating Concrete Systems combines lightweight concrete and expanded polystyrene foam. They provide a smooth, monolithic surface ideal for roofing, and help to prolong the life of the roof membrane by lowering membrane temperatures. These systems address roof design goals such as slope-to-drain, moisture resistance, compressive strength, stability, and mechanical fastening. They also meeting regulatory requirements for Florida Building Code, Factory Mutual, UL, CSA, and many others.
One significant advantage is their potential reusability. LWIC is high resistant to moisture damage, allowing for reroofing in most cases. This can help reduce the life cycle cost of the roof system and minimize solid waste.
What happens if it rains while the contractor is installing the LWIC system?
In comparison to polyisocyanurate insulation boards where rain may lead to a tear out due to board damage, decreased thermal resistance, and potential mold growth, the remediation required for LWIC systems is less complicated.
- If rain occurs while the contractor is placing the board in the slurry, the system is typically unaffected and can be fixed or touched up the by the LWIC applicator once the rain subsides.
- During the installation of the top coat, if it starts raining, there is a possibility of small pitting occurring. However, this generally does not impact the roof’s attachment, whether it’s nailed base sheet or a single-ply membrane.
- In the event of a heavy rain, there might be some runoff of the top coat. This can be addressed and repaired by the LWIC applicator on the following day.
- Contact your local field tech representative with questions.
Why use LWIC versus traditional insulation like ISO?
LWIC can reduce the need for insulation replacement during reroof cycles. This not only saves you time, effort, and expense of replacing your insulation every time you replace your roof, but it can also help reduce the waste from your project that needs to be disposed of in a landfill. All while potentially extending the life of your roofing membrane by lowering membrane temperatures. A win-win scenario!
Unlike ISO insulation, which demands perfection in substrate surfaces, LWIC application is not affected by superficial imperfections like uneven substrates. With LWIC, an additional slurry coat smooths out any irregularities, providing a smoother surface of the insulation system.
Installing over existing roofs
The preparation of these roof systems involves the following steps:
- Remove loose gravel or overburden
- Making repairs to ensure the roof is watertight, simlar to a temporary roof or vapor barrier.
- Pouring the LWIC system of choice.
How much does LWIC weigh?
LWIC is approximately 8 lbs psf wet and 6 lbs psf dry.
How does LWIC provide UL Deck Fire Ratings?
LWIC has a significant advantage over rigid insulation systems when it comes to deck design and fire ratings. In a typical metal deck assembly with rigid insulation, the entire underside of the metal deck needs to be sprayed with fireproofing. However, with LWIC, only the structural members required fireproofing. This can help eliminate approximately 95% of the fireproofing required for a project.
By reducing the amount of fireproofing required, LIWC can be a cost-saving option compared to rigid insulation systems.
Does LWIC contribute to Acoustic Design for buildings?
Using lightweight insulating concrete for acoustics in a roof can provide several benefits, including:
- Sound insulation: Lightweight insulating concrete is an excellent material for reducing airborne sound transmission. Its dense composition and high mass help absorb and dampen sound waves, helping to prevent them from passing through the roof structure. This can significantly reduce noise from external sources, such as traffic, aircraft, or nearby industrial activities, leading to a quieter indoor environment.
- Noise reduction within the building: Lightweight insulating concrete can also improve sound insulation within the building itself. It helps minimize sound transmission between different floors or rooms, reducing the transfer of unwanted noise and promoting acoustic privacy. This is particularly beneficial in environments where noise control is important, such as offices, hospitals, educational institutions, or residential buildings.
How does LWIC impact aging of roof membranes?
How does the temperature of a roof membrane affect its aging rate?
Raising the temperature of a roof membrane by 18 degrees Fahrenheit doubles it aging rate. Therefor, maintaining a cooler temperature for the roof membrane can significantly extend its lifespan.
How does LIWC contribute to keeping the roof membrane cooler?
LWIC helps maintain the roof membrane’s cooler temperature by absorbing a portion of the energy. This has been coined as an absorption process known as the “mass effect”.
Why does LWIC slow down the aging of roof membranes?
The mass of the LWIC system plays a crucial role in slowing down the aging process of roof membranes. By having the LWIC topping placed above the Insulperm board, the LWIC can absorb some of the energy that would otherwise impact the roof membrane directly. This absorption reduces stress on the membrane over time and helps prolong its lifespan.
How does polyisocyanurate compared to LWIC in terms of energy absorption?Polyisocyanurate, due to its lower mass, lacks the capability to absorb energy effectively. As a result, it fails to alleviate the energy stress on the roof membrane. In contrast, LWIC, with its higher mass, can absorb a significant amount of energy and limit the impact on the roof membrane.
What happens if it rains on the lightweight before it is roofed?
Moderate Rain is a common occurrence that should not pose any major issues for a properly installed LWIC system.
- The drying process will need to be extended depending on the amount of rain that has affected the LWIC deck.
- Generally, an additional day of drying time is required.
In extreme cases, if a severe storm occurs and deposits a significant amount of rain in a short period, some water extraction may be necessary.
- Extraction involves cutting an opening near a drain or a low-lying area on the deck and using a vacuum to remove the water before starting the roofing process.
How long does it take for the LWIC to cure and be ready to roof?
The general guideline for LWIC curing is 48 to 72 hours, although this can vary depending on weather conditions and ambient temperatures. If temperatures consistently average below 50 degrees Fahrenheit, the curing time may be extended.
How long can LWIC stay exposed before installing the roof?
Cellular light concrete roofs system to be roofed over within 10 days. However, extended exposure LWIC substrates is possible in certain cases. For cellular LWIC, roof installation should occur promptly of if the LWIC is dry enough.
Why are there cracks forming in the LWIC?
Cracks in the top pour of Cellular decks are common as the LWIC mix dries and shrinks. These cracks are typically superficial.
Are roof vents required?
Roof vents are required for LWIC systems. They can be achieved through One-Way Vents and venting flashing details at walls and curbs. Place One-Way Vents every 1000 square feet.
How is slope achieved with LWIC?
Slope is achieved by staggering the heights of the Insulperm (EPS)
Can the Insulperm be left out overnight without having the top layer of lightweight concrete completed?
It is common practice to leave the exposed Insulperm set in the slurry overnight to allow the slurry to dry before applying the top coat.
Can LWIC be installed over a painted metal deck?
For proper installation on metal decks, it is crucial to apply LWIC directly to galvanized metal decks only. The PH of galvanized steel stops the oxidation or rusting where paint could flake and rust.
In cases where a painted metal deck has been utilized, the inclusion of a temporary roof assembly becomes necessary to create a barrier between the LWIC and the painted metal deck. Installing LWIC directly over painted metal decks can result in premature rusting of the underlying metal deck.
How do we keep LWIC from pouring into the building below at openings in the deck on New Construction Projects?
LWIC contractors should take the following precautions to prevent excess material flowing into the space.
- Pour stops are utilized by the contractors to surround drains, openings, and penetrations in the deck, including the perimeter, to minimize material overflow.
- In the case of a new construction roof area, during the inital day of pouring, there may be some minor dripping observed.
- Typically, by the second day, the dripping issue subsides allowing work to proceed underneath the roof area.
