Which is best for me - 80% or 90% Block?
Some Differences in Performance: The 80% material does a great job rejecting heat and glare. The 90% block is recommended for situations where maximum rejection of heat and glare is desired. The amount of light received is marginally more with the 80% block than it is with the 90%. Outward visibility is achieved with either option.
Interior Lighting Considerations
The 90% material blocks somewhat more solar heat (about 10%) than the 80%, and because of the tighter weave, it blocks slightly more light. If your skylight is the only source of natural light in a particular area, for example, a hallway or bathroom without windows, the 80% material may be the better option. If the room receives natural light from other windows, the 90% material should work well.
Outside Appearance for Dome or Curved Skylights
Because the 90% material is heavier and more rigid, it does not conform to the curvature of the dome shaped lens as well as the 80%. Pleating in the diagonal corners is slightly more pronounced for the 90% material. Over time, as the material relaxes, the pleating effect will lessen. This is not an issue for flat or non curved surfaces.
Your choice depends on your personal preference. The heat blockage and light transfer between the two choices is only about 10%.
Considerations for 80% vs. 90% Material
The 80% material does a great job rejecting heat and glare. The 90% material is offered for situations where maximum heat and glare rejection is the goal while retaining the ability to receive light and see the outside environment.
The 90% material does block slightly more solar heat than the 80% material (about 10%) and because it is made with a tighter weave, it will restrict slightly more light.
If your skylight is the only source for natural light in an area (for example, an interior room and some bathrooms without windows) the 80% choice may be preferable.
If the space is open and receives natural light from other windows, the 90% material may meet your need.
The choice depends on your personal preference, weighing your own heat gain and interior light issue.