Tips to Prevent Condensation in Polycarbonate Sheets

Polycarbonate sheets cannot be sealed completely airtight, so small amounts of condensation are at times unavoidable. Large droplets or excessive condensation, however, can be a sign of incorrect installation or poor drop trim, and can negate the point of installing the polycarbonate structure in the first place, so it’s worth ensuring you’re attempting to avoid condensation as much as possible.

What Causes Condensation in Polycarbonate Sheets?

There are a number of common causes of condensation:

• The drip trim supporting the bar cap is not sealed
• The drop trim has not been sealed with compatible sealant
• The drip trim is cracked or warped and is of poor quality
• The filter tape has become damp before installation (usually due to damp storage conditions or being fitted on a wet day and left in the rain)
• Filter tape has come into contact with detergents in cleaning water which has broken down any water repellent qualities
• Heat has evaporated water from the structure which has re-condensed further up the flute chambers

All of these factors can be immediately apparent but they also may take time to appear once the right temperature or humidity is reached.

6 Ways to Reduce Condensation

1. Before installation, ensure your polycarbonate sheets are clean and dry – any small amount of moisture can turn into condensation once installed.
2. Apply anti-dust filter tape to the ends of the sheet – it is critical this tape adheres properly to the multiwall polycarbonate.
3. Ensure you choose a good quality drip trim that will withstand weather extremes over time. It may be better to choose an aluminium drip trim as opposed to PVC for longevity and added strength.
4. Push a high quality endstop bar over the top of the lower end of your polycarbonate. Ensure this is only pushed part way on, just further than the anti-dust filter tape, then run a continuous bead of quality low-modulus neutral-cure, compatible sealant in front of the upper leading edge of the endstop bar.
5. Push the endstop bar so the leading edge rides over the sealant and forms a watertight seal, leaving a four millimetre gap between the face of the anti-dust filter tape and the inside face of the endstop Bar.
6. Finally, seal the joints between the glazing caps of the endstop bar should be sealed with a low-modulus neutral-cure sealant to prevent any water from entering the end of the trim. There should be no gaps between the endstop bar and glazing caps either side.

Please consider that these steps are intended to assist installers in avoiding condensation upon initial installation – if you already have condensation and repairs and remedial work is needed, ensure the roof sheets  are dried thoroughly before attempting re-installation.

For more help, get in contact with our expert team, or shop polycarbonate sheets here.