Tapered Polyisocyanurate Design: Expectations vs. Limitations

A 4-Way design directly to the drain is the most efficient design for getting water off your roof, but there may be factors that prevent you from utilizing this option. There are countless designs to match your criteria and knowing what they are and what the pros and cons are of each design are will give you an understanding of what to expect.

The first thing to address is: what your main objective for this design is. Getting water off the roof efficiently, budget, minimizing heights, and ease of installation could all be factors. To help determine the main objective for your design, below are three options to consider.

4-Way Design – Best option when getting water off the roof is the biggest priority

Pros:

• Very efficient
• No flat spots occur in this design

Cons:

• Expensive
• Heights can get high pretty fast
• No flexibility to accommodate areas where low heights are required
• Can be difficult to install

Modified 4-Way Design – Preferred option when budget, expense, or heights are a concern

Pros:

• Can minimize heights while still maintaining the integrity of a 4-Way Design
• Good first step at minimizing cost
• Can be used to keep perimeter heights consistent
• Installation can be easier than a full 4-Way Design

Cons:

• Introduces crickets to your design (expect birdbaths at the very least)

2-Way with Crickets Design – Great option when budget, heights, and ease of installation are the priority

Pros:

• Flexibility to keep heights low around areas required
• The most inexpensive design available
• Easy installation

Cons:

• Will be a lot of crickets utilized with this option
• The more crickets used means more areas of birdbaths
• The narrower the cricket, the less effective it becomes at moving water
• Has the potential for areas of sitting water

As you can see, going down the list of designs, the amount of water that can be left on your roof increases. When designing your roof, it is always best to create a checklist of items that can affect the design. Using this list will give you a basic understanding of what to expect when it comes to performance. The best course of action is to forward that list to the manufacturer, and they can create a design based on all of your requirements.

For more information on tapered Polyiso insulation, please contact your Carlisle SynTec Manufacturer's Representative.