Moisture/Vapor Control
Vapor retarders are used to impede the passage of water vapor into roofing systems, thereby preventing condensation and resulting damage to the insulation and roof system. All Atlas Roof Insulation Products may be installed with or without a vapor retarder, the need for which is determined by the designer. The designer may consult the NRCA Roofing and Waterproofing Manual for guidance in determining the need for a vapor retarder. Special consideration should be given to construction-generated moisture, as well.  For example, construction-generated moisture, such as will be released by placing concrete floor slabs after the roof has been installed, can drive large quantities of moisture into the roof system. Therefore, Atlas cannot be responsible for damage to the insulation when exposed to construction-generated moisture. Refer to the NRCA Roofing and Waterproofing Manual for their recommendations for the use of a vapor retarder when construction-generated moisture is present (4th Edition, Volume 1, p. 121). Refer to Atlas Technical Bulletin #00-01.

Concrete Decks
Cast-in-place structural concrete, lightweight insulating concrete and poured gypsum decks require special consideration to address the large amounts of inherent moisture. Consult the NRCA Roofing and Waterproofing Manual for recommendations and instructions.  See "Mechanical Attachment" below.

Single-Ply Membrane Systems

Fully Adhered Single-Ply Membrane Systems
ACFoam® -II, and Tapered ACFoam® are the most commonly specified products in fully adhered single-ply membrane systems. When a single-ply membrane is specified for direct application to ACFoam-II, the ACFoam-II should be installed with the unmarked side up, using only one adhesive application to the insulation. The adhesive should be applied in strict accordance with the manufacturer´s instructions, and must be allowed to dry sufficiently to become tacky to the touch before the single-ply membrane is applied.

For cold weather applications, the membrane adhesive should be applied at the temperature recommended by the membrane manufacturer. Do not thin the adhesive with solvents, which can adversely affect the insulation. Failure to allow the adhesive solvents to evaporate or failure to protect the insulation from damage can cause the facer and membrane to separate from the foam core.

Some designers, consultants, and industry organizations recommend the use of a coverboard in adhered single-ply applications. Consult the membrane manufacturer for recommendations regarding coverboard requirements. The use of a coverboard may change the fastening requirements or fire/wind ratings.

Multi-Layer Application of Insulation - A two-layer application of Atlas Roof Insulation is strongly recommended. The joints in each layer should be offset in order to avoid a vertically continuous joint through the total insulation thickness. Two layers (or more) with joints staggered can provide improved insulation performance by eliminating thermal bridges. This method also reduces condensation potential and thermal stress on the roof membrane (refer to Technical Bulletin #00-01).

Multi-layer Application: A two layer application of ACFoam is strongly recommended for fully adhered membranes. Atlas recommends a maximum 2.7" thick top layer. (Above)

Mechanically Attached Single-Ply Membrane Systems
ACFoam®-II, ACFoam®-III, Tapered ACFoam®, and ACFoam® Supreme® may be used under this membrane system. The insulation should be attached with FM Approved fasteners in accordance with the fastening patterns shown.ACFoam®-III is especially recommended for this application.

Mechanical Attachment
Mechanical fastening is the recommended method of attachment over nailable decks. Fastener frequency and spacing for steel, wood, concrete and poured gypsum decks are covered in the current Atlas Sweet´s Catalog according to the membrane system. Refer to FM Loss Prevention Data Sheet 1-29 for special considerations regarding perimeter and corners of the roof. For fastening patterens in corners and perimeter of roof, see fastening patterns on this website.  For proper attachment of insulation to lightweight insulating concrete decks or poured gypsum concrete decks, follow the instructions outlined in the NRCA Roofing and Waterproofing Manual. Atlas Roof Insulation products must not be adhered directly to these decks by any bitumen or adhesive attachment method.

Loose-Laid Ballasted Single-Ply Membrane Systems
All ACFoam® products may be used with ballasted systems. Atlas does not require attachment of the insulation in this system; however, for projects insured by FM or that require FM compliance, refer to FM Loss Prevention Data Sheets. All installed insulation must fit together tightly to prevent separation, movement and damage during membrane installation. After the membrane is installed, sufficient amounts of ballast must be applied to prevent insulation and membrane movement.

Recover Board Applications
ACFoam® Recover Board® is specified for recover applications and should be attached as shown when used in a mechanically fastened single-ply system. (Check with the membrane manufacturer regarding approvals of this product as a membrane substrate and fastening rates for fully adhered systems.)

ACFoam Recover Board Fastening Patterns For Mechanically Attached Systems:

When installing any ACFoam product, care should be taken to ensure that joints are placed solidly on the bearing surface of the roof decking.

BUR & Modified Bitumen Systems
ACFoam®-II, ACFoam® Composite and Tapered ACFoam® are used in BUR and modified bitumen membrane systems. Do not torch apply modified bitumen systems directly to any ACFoam product. Membranes may be hot mopped directly to the perlite side of ACFoam Composite. When using ACFoam-II, a separation layer is recommended. Check with membrane manufacturer for recommended installation procedures.

Separation Layer: The use of a separation layer means that ACFoam-II is covered with one of the following prior to membrane application:

• A spot-mopped glass base sheet.
• A strip-mopped glass base sheet with approximately 4" wide strips and approximately 8" wide spaces between strips.
• A vented-glass base sheet, properly applied.
• A mopped minimum 1/2 " wood fiberboard, mopped minimum 1/2" perlite board, glass or mineral fiber board.

The ACFoam should be attached with FM Approved fasteners in accordance with the fastening patterns indicated below:

Bitumen Attachment
For installing ACFoam-II®, ACFoam® Composite and Tapered ACFoam® to a structural concrete deck, bitumen attachment is the recommended method. When using asphalt on concrete decks, priming is necessary. Precautions must be taken to prevent bitumen drippage. When using hot-applied bitumen for attachment, the deck must be dry and care must be taken to apply the bitumen in sufficient quantity to totally cover the available deck surface. Use 18 to 30 pounds of bitumen per square to ensure proper attachment. To ensure embedment, the board must also be "stepped in" at several points while the bitumen is still hot enough to allow positive attachment. The recommended ACFoam insulation size for hot asphalt attachment is 4´ x 4´. Because of the unevenness of structural concrete decks, 4´ x 8´ boards are not recommended for bitumen attachment to the deck. 4´ x 8´ boards may, however, be mechanically fastened.

Bitumen Temperature
The bitumen should be applied at the Equiviscous Temperature (EVT) ±25¡F. The bitumen used must have a temperature no higher than 450F at the point of contact with ACFoam products.

Metal Roof Installation Recommendations

Metal Roof Systems
Any ACFoam® product can be used under metal roof systems fastened through the insulation into the roof deck. ACFoam® Nail Base Insulation (NBI) and Vented-R®, featuring an OSB top surface, are ideal for supporting fastening clips.

Consult the metal roof panel manufacturer for insulation attachment details. In the absence of metal roof panel manufacturers´ recommendations for insulation attachment, pre-secure NBI or Vented-R in accordance with Atlas Guide Details for Nail Base and Vented-R.

Consult the metal roof panel manufacturer for insulation attachment details. In the absence of metal roof panel manufacturers´ recommendations for insulation attachment, fasten ACFoam-II or Supreme as a minimum with FM approved fasteners and insulation plates at the rate of 1 fastener per 6.4 sq.ft., see Mechanically Attached Membrane Systems.

Slab Installation Recommendations

Slab Insulation
ACFoam® Supreme 25 psi features Atlas closed-cell polyiso with tri-laminate foil facers to provide the highest possible per inch R-values. ACFoam Supreme 25 psi is specified for use under the slab of low temperature warehouses and cold storage buildings. The increased compressive strength and highest R-value available makes this product ideal for low temperature applications.

Install the first layer of ACFoam Supreme 25 psi over the sub-slab and vapor retarder. Butt the panels tightly together and stagger the end joints in each row. Install the second layer so that the joints in each layer are offset in order to avoid a vertically continuous joint through the total insulation thickness. If a third layer is specified, repeat the offset process, butting the panels tightly.

The concrete working slab may be applied directly over the ACFoam Supreme 25 psi.The ACFoam Supreme 25 psi should be tightly butted together. Any gaps between insulation boards greater than 1/4" should be taped with foil tape.