This is the continuation of “Metal Roofing Performance (Part 1)”. Haven’t read it yet? You can read it from this link here.
Another unfortunate approach to installing a metal roof is to install the new roof over the existing material. This is justified by claiming that this is a green approach, avoiding the cost and mess of a roof tear-off, adding “additional insulation”, and preventing “more landfill debris”. The deficiencies of this approach to the homeowner will become apparent later, and include:
- Additional weight to the roof structure
- Existing roof deck deterioration will continue, but is now hidden under two roof coverings
- Waterproofing membrane cannot be installed over the old roof, reducing protection of the “new” roof assembly from water infiltration
- The old roof covering becomes a sponge if a leak occurs, making it much harder to determine the true source of the leak without disassembling the new roof
- Roof penetrations are usually sealed only with caulking (which can fail in as little as five years), instead of being properly waterproofed and sealed from the deck up.
- The addition of outlet vents does not replace a proper evaluation of the insulation/ventilation behavior of the roof. They may actually reduce the performance of the roof system, if the evaluation was not properly done.
To make a metal roof installation a “green” installation, it will need both longevity and performance. The performance comes from how the product is married to the existing structure, and the repair of deficiencies that may exist. To get a “green” roof, the roof system needs to be properly assessed, deficiencies found and corrected, the preparation of the roof be properly done and the roof covering be installed with all the additional safeguards in place. Only then will you have the longevity and performance that you should expect.
To summarize: To get a “green” roof the following should occur:
- The product used should be long-lasting (with a track record of performance and durability)
- At a minimum, the product should be installed following the manufacturer’s instructions AND current best practices (which are location-specific)
- The roof system should be assessed to ensure that deficiencies are fully identified, and that appropriate actions are taken to minimize or eliminate the deficiencies. This means that a full inspection (both interior and exterior) be done, the insulation and ventilation capacities are measured and compared to the required standards, and observed deficiencies are discussed with the homeowners
- The roof (with very few exceptions) should be stripped to the deck
- The corrective actions identified in #3 above, be performed
- The appropriate layering of waterproofing, flashing and sealing be carried out to counter the usual modes of roofing failure
- If the deficiency correction cannot be done (for budgetary or technical reasons), then appropriate measures be designed to minimize the damage that could be caused by those deficiencies
- The “green” marketing claims can be verified by incorporation of specific features (of either product or installation) that deliver the performance claimed
Renoteck Roofing has years of experience with the Calgary weather and metal roofing. They can be trusted with making the correct assessments of your situation. They will guide you to make the decision that is right for you.